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Applied Surface Science (v.256, #14)

A novel chemical synthesis and characterization of Mn₃O₄ thin films for supercapacitor application by D.P. Dubal; D.S. Dhawale; R.R. Salunkhe; S.M. Pawar; C.D. Lokhande (pp. 4411-4416).

Mn₃O₄ thin films have been prepared by novel chemical successive ionic layer adsorption and reaction (SILAR) method. Further these films were characterized for their structural, morphological and optical properties by means of X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), field emission scanning electron microscopy (FESEM), wettability test and optical absorption studies. The XRD pattern showed that the Mn₃O₄ films exhibit tetragonal hausmannite structure. Formation of manganese oxide compound was confirmed from FTIR studies. The optical absorption showed existence of direct optical band gap of energy 2.30eV. Mn₃O₄ film surface showed hydrophilic nature with water contact angle of 55°. The supercapacitive properties of Mn₃O₄ thin film investigated in 1M Na₂SO₄ electrolyte showed maximum supercapacitance of 314Fg⁻¹ at scan rate 5mVs⁻¹.

Keywords: Mn; ₃; O; ₄; thin films; SILAR; Surface morphology; Supercapacitor

Growth and field emission property of coiled carbon nanostructure using copper as catalyst by Zhejuan Zhang; Pingang He; Zhuo Sun; Tao Feng; Yiwei Chen; Huili Li; BengKang Tay (pp. 4417-4422).

Coiled carbon nanostructure (CNS) is prepared by a catalytic chemical vapor deposition (CVD) process on copper/chromium films deposited by radio frequency (RF) sputtering. Uniform CNS with coiled structure is fabricated by changing the size of the catalyst particles. The effects of Cu catalyst size and RF sputtering power, on the growth of the coiled CNS are discussed, and the results importantly conclude that Cu-catalyzed CVD offers a preferable control of coiled CNS to optimize the field emission property for application.

Keywords: Copper catalyst; Coiled carbon nanostructure; Field emission property

Influence of growth temperature of TiO₂ buffer on structure and PL properties of ZnO films by Weiying Zhang; Jianguo Zhao; Zhenzhong Liu; Zhaojun Liu; Zhuxi Fu (pp. 4423-4425).

A series of ZnO films with TiO₂ buffer on Si (100) substrates were prepared by DC reactive sputtering. Growth temperature of TiO₂ buffer changed from 100°C to 400°C, and the influence on the crystal structures and optical properties of ZnO films have been investigated. The XRD results show that the ZnO films with TiO₂ buffer have a hexagonal wurtzite structure with random orientation, and with the increase of growth temperature of TiO₂ buffer, the residual stresses were released gradually. Specially, the UV emission enhanced distinctly and FWHMs (full width half maximum) decreased linearly with the increasing TiO₂ growth temperature. The results all come from the improvement of crystal quality of ZnO films.

Keywords: Buffer layer; TiO; ₂; Growth temperature; ZnO

Fabrication of polyindene and polyindole nanostructures by Shubhra Goel; Nasreen A. Mazumdar; Alka Gupta (pp. 4426-4433).

One-dimensional (1D) nanostructures of fused ring polymeric systems: polyindene (PIn) and polyindole (PInd) were fabricated onto glass substrates using a chemical vapor deposition (CVD) method. Morphology of fabricated PIn and PInd structures studied using Olympus microscope reveals formation of 1D straight tubular, smooth and fluorescent nanostructures. The results obtained were further correlated with scanning electron microscopic (SEM) studies of PIn and PInd nanostructures, indicating appearance of fine nanothread entangled network (having diameter∼50nm) for PIn, and well-defined, straight and aligned nanotubes (having diameter∼60nm) for PInd. A comparative study on the morphology/dimensions of fabricated PIn and PInd nanostructures with the nanosized PIn and PInd structures obtained by oxidative synthetic routes is also discussed. The structural composition of fabricated PIn and PInd nanostructures is confirmed by Fourier transform infrared (FTIR) spectroscopy, thereby indicating existence of all infrared markers corresponding to the characteristic bands present in PIn and PInd. The study suggests that the fabricated PIn and PInd nanodimensional structures may find potential applications in the field of nanotechnology.

Keywords: Polyindene; Polyindole; Nanostructures; Microscopy; Surface morphology; Infrared spectroscopy

Mechanism of aluminum hydroxide layer formation by surface modification of aluminum by Young Ik Seo; Young Jung Lee; Dae-Gun Kim; Kyu Hwan Lee; Young Do Kim (pp. 4434-4437).

In this study, a new, relatively simple and rapid fabrication method for forming an Al(OH)₃ film on Al substrates was demonstrated. This method, i.e., alkali surface modification, is simply comprised of dipping the substrate in a 5×10⁻³M NaOH solution at 80°C for 1min and then immersing it in boiling water for 30min. After alkali surface modification, an Al(OH)₃ film was formed on Al substrate, and its chemical state and crystal structure were confirmed by XPS and TEM. The Al(OH)₃ layer was composed of three regions: an amorphous-rich region, a region of mixed amorphous and crystal domains, and a crystalline-rich region near the Al(OH)₃ layer surface.

Keywords: Akali surface modification; Aluminum hydroxide; Mesoporous surface; Gibbsite

Determination of electrical types in the P-doped ZnO thin films by the control of ambient gas flow by Young Yi Kim; Won Suk Han; Hyung Koun Cho (pp. 4438-4441).

Phosphorus (P)-doped ZnO thin films with amphoteric doping behavior were grown on c-sapphire substrates by radio frequency magnetron sputtering with various argon/oxygen gas ratios. Control of the electrical types in the P-doped ZnO films was achieved by varying the gas ratio without post-annealing. The P-doped ZnO films grown at a argon/oxygen ratio of 3/1 showed p-type conductivity with a hole concentration and hole mobility of 1.5×10¹⁷cm⁻³ and 2.5cm²/Vs, respectively. X-ray diffraction showed that the ZnO (0002) peak shifted to lower angle due to the positioning of P³⁻ ions with a larger ionic radius in the O²⁻ sites. This indicates that a p-type mechanism was due to the substitutional P_O. The low-temperature photoluminescence of the p-type ZnO films showed p-type related neutral acceptor-bound exciton emission. The p-ZnO/ n-Si heterojunction light emitting diode showed typical rectification behavior, which confirmed the p-type characteristics of the ZnO films in the as-deposited status, despite the deep-level related electroluminescence emission.

Keywords: Zinc oxide; p; -Type; Sputtering; Amphoteric doping

Fabrication and hard X-ray photoemission analysis of photocathodes with sharp solar-blind sensitivity using AlGaN films grown on Si substrates by Masatomo Sumiya; Yutaro Kamo; Naoki. Ohashi; Masaki Takeguchi; Yoon-Uk Heo; Hideki Yoshikawa; Shigenori Ueda; Keisuke Kobayashi; Tokuaki Nihashi; Minoru Hagino; Takayuki Nakano; Shunro Fuke (pp. 4442-4446).

Photocathode devices operating in reflection-mode, where the photoemission is detected on the same side as the light irradiation, were developed for the detection of deep ultraviolet light by using p-Al_xGa1−_xN films grown on Si(111) substrates. The external quantum efficiencies were as high as 20–15% at 200 nm and 280nm, while the value was as low as 10⁻²% at 310nm. The on–off ratio was more than four orders of magnitude, which represents high solar-blind sensitivity. The escape probability of Al_xGa1−_xN photocathode was decreased with increase of AlN mole fraction. The effective barrier potential against the photoelectron emission near the surface was reduced due to the upward shift of conduction band of Al_xGa1−_xN. The photoemission from the Al_xGa1−_xN films terminated with Cs–O adatoms will be discussed in terms of band diagrams that were evaluated by hard X-ray photoelectron spectroscopy.

Keywords: Photocathode; III–V nitride; Hard X-ray photoelectron spectroscopy

Adsorption of 2-nitrophenol by multi-wall carbon nanotubes from aqueous solutions by R. Arasteh; M. Masoumi; A.M. Rashidi; L. Moradi; V. Samimi; S.T. Mostafavi (pp. 4447-4455).

Adsorption of 2-nitrophenol in aqueous phase on multi-wall carbon nanotubes (MWNTs) and functionalized multi-wall carbon nanotubes having covalent attachments of carboxylic groups (MWNTs-COOH) has been considered. Adsorption behavior of 2-nitrophenol onto carbon nanotubes was studied by varying the parameters such as agitation time, 2-nitrophenol concentration and pH. The presence of surface functional groups affected the adsorption capacity of MWNTs for this removal of 2-nitrophenol. Kinetic studies were performed and pseudo-second-order kinetic model successfully represented the kinetic data. The Freundlich, Langmuir and Tempkin adsorption models were used for the mathematical description of adsorption equilibrium and it was found that the experimental data fitted very well to the Langmuir model. However, for MWNTs-COOH, Tempkin model may be recommended because of the strong adsorbent–adsorbate interactions arising from the functional groups present on the surface of MWNTs. The results of the study show that the carbon nanotubes can be used as potential adsorbent for phenolic derivate in water/wastewater.

Keywords: MWNTs; 2-Nitrophenol; Adsorption; Kinetics; Isotherms

Molecular imaging of in vivo calcium ion expression in area postrema of total sleep deprived rats: Implications for cardiovascular regulation by TOF-SIMS analysis by Fu-Der Mai; Li-You Chen; Yong-Chien Ling; Bo-Jung Chen; Un-In Wu; Hung-Ming Chang (pp. 4456-4461).

Excessive calcium influx in chemosensitive neurons of area postrema (AP) is detrimental for sympathetic activation and participates in the disruption of cardiovascular activities. Since total sleep deprivation (TSD) is a stressful condition known to harm the cardiovascular function, the present study is aimed to determine whether the in vivo calcium expression in AP would significantly alter following TSD by the use of time-of-flight secondary ion mass spectrometry (TOF-SIMS) and calretinin (a specific calcium sensor protein in AP neurons) immunohistochemistry. The results indicated that in normal rats, the calcium intensity was estimated to be 0.5×10⁵ at m/ z 40.08. However, following TSD, the intensity for calcium ions was greatly increased to 1.2×10⁵. Molecular imaging revealed that after TSD, various strongly expressed calcium signals were distributed throughout AP with clear identified profiles instead of randomly scattered within this region in normal rats. Immunohistochemical staining corresponded well with ionic image in which a majority of calcium-enriched gathering co-localized with calretinin positive neurons. The functional significance of TSD-induced calcium augmentation was demonstrated by increased heart rate and mean arterial pressure, clinical markers for cardiovascular dysfunction. Considering AP-mediated sympathetic activation is important for cardiovascular regulation, exaggerated calcium influx in AP would render this neurocircuitry more vulnerable to over-excitation, which might serve as the underlying mechanism for the development of TSD-relevant cardiovascular deficiency.

Keywords: Calcium; Sleep deprivation; Area postrema; TOF-SIMS; Cardiovascular regulation; Quantitative immunohistochemistry

Influence of temperature annealing on optical properties of SrTiO₃/BaTiO₃ multilayered films on indium tin oxide by T. Supasai; S. Dangtip; P. Learngarunsri; N. Boonyopakorn; A. Wisitsoraat; Satreerat K. Hodak (pp. 4462-4467).

We have prepared SrTiO₃/BaTiO₃ thin films with multilayered structures deposited on indium tin oxide (ITO) coated glass by a sol–gel deposition and heating at 300–650°C. The optical properties were obtained by UV–vis spectroscopy. The films show a high transmittance (approximately 85%) in the visible region. The optical band gap of the films is tunable in the 3.64–4.19eV range by varying the annealing temperature. An abrupt decrease towards the bulk band gap value is observed at annealing temperatures above 600°C. The multilayered film annealed at 650° C exhibited the maximum refractive index of 2.09–1.91 in the 450–750nm wavelength range. The XRD and AFM results indicate that the films annealed above 600° C are substantially more crystalline than the films prepared at lower temperatures which were used to change their optical band gap and complex refractive index to an extent that depended on the annealing temperature.

Keywords: PACS; 78.20.CiPerovskites; Optical properties; Multilayers; Annealing; Sol–gel

Solution-processed p-doped hole-transport layer and its application in organic light-emitting diodes by Xinwen Zhang; Zhaoxin Wu; Dawei Wang; Dongdong Wang; Runlin He; Xun Hou (pp. 4468-4472).

We investigate p-type doping poly(9-vinylcarbazole) (PVK) hole-transport layer (HTL) with tetrafluoro-tetracyano-quinodimethane introduced via cosolution. We found that the performances of devices with doped HTLs are significantly improved. The efficiency and lifetime of the p-doped device are 2.3 and 3.7 times as large as that of the control device with pure PVK as a HTL. Furthermore, the turn-on voltage of the device is reduced from 9.5 to 3.6V by using a p-doped HTL. These improved properties are attributed to the formation of the charge-transfer complex in the HTL, which increases hole injection and conductivity of p-doped films considerably.

Keywords: Organic light-emitting diodes; Solution-processed; p-Doped hole-transport layer; Stability

Efficient epoxidation over cyanocobalamine containing SBA-15 organic–inorganic nanohybrids by Z. Karimi; A.R. Mahjoub (pp. 4473-4479).

SBA-15 mesoporous silica is synthesized using triblock copolymer P123 surfactant and chemically modified by aminopropyl, thiol, ammonium and sulfonic acid functional groups. Functionalization is performed via post synthesize method using 3-aminopropyltriethoxysilane (APTES) or 3-mercatopropyl trimethoxysilane (MPTMS) precursor. The as synthesized mesoporous systems are applied for immobilization of cyanocobalamine. Functionalization effectively improves sorption properties of the supports, while different functional groups exert different effects. The organic–inorganic mesoporous materials are characterized via X-ray diffraction (XRD), nitrogen adsorption and desorption, transmission electron microscopy (TEM), FT-IR and inductively coupled plasma-optical emission (ICP). The newly synthesized systems exhibit high catalytic activity for heterogeneous epoxidation of cyclooctene in presence of hydrogen peroxide. Reaction conditions are optimized, effect of functional groups on performance of the catalysts is taken into consideration and reusability of the designed heterogeneous systems is studied. Systems with chemically modified supports are shown to be more efficient and stable catalysts however; chemical nature of functional groups plays a crucial role.

Keywords: Functinalization; SBA-15; Cyanocobalamine; Heterogeneous catalyst; Epoxidation

p-Chlorophenol adsorption on activated carbons with basic surface properties by Ewa Lorenc-Grabowska; Grażyna Gryglewicz; Jacek Machnikowski (pp. 4480-4487).

The adsorption of p-chlorophenol (PCP) from aqueous solution on activated carbons (ACs) with basic surface properties has been studied. The ACs were prepared by two methods. The first method was based on the modification of a commercial CWZ AC by high temperature treatment in an atmosphere of ammonia, nitrogen and hydrogen. The second approach comprised the carbonization followed by activation of N-enriched polymers and coal tar pitch using CO₂ and steam as activation agent. The resultant ACs were characterized in terms of porous structure, elemental composition and surface chemistry (pH_PZC, acid/base titration, XPS). The adsorption of PCP was carried out from an aqueous solution in static conditions. Equilibrium adsorption isotherm was of L2 type for polymer-based ACs, whereas L3-type isotherm was observed for CWZ ACs series. The Langmuir monolayer adsorption capacity was related to the porous structure and the amount of basic sites. A good correlation was found between the adsorption capacity and the volume of micropores with a width <1.4nm for polymer-based ACs. Higher nitrogen content, including that in basic form, did not correspond to the enhanced adsorption of PCP from aqueous solution. The competitive effect of water molecule adsorption on the PCP uptake is discussed.

Keywords: Activated carbon; Surface basic sites; Adsorption; Phenols

Nitrogen doping-mediated room-temperature ferromagnetism in insulating Co-doped SnO₂ films by X.F. Liu; Javed Iqbal; S.L. Yang; B. He; R.H. Yu (pp. 4488-4492).

Co-doped SnO₂ films codoped with nitrogen (N) have been prepared by magnetron sputtering to investigate the effect of p-type defects on magnetic properties. The incorporation of N modifies the preferential growth orientation of the films. Multiple characterization techniques reveal that the incorporated Co²⁺ and N³⁻ ions substitute for Sn⁴⁺ and O²⁻ sites in SnO₂ lattice, respectively. As N concentration increases, the band gap of the films decreases because of the formation of Sn–N bond. Room-temperature ferromagnetism is observed in (Co,N)-codoped SnO₂ films, and the saturated magnetic moment is sensitive to the incorporated N concentration. The variations in the magnetic properties as a function of N concentration are discussed on the basis of bound magnetic polaron model.

Keywords: Diluted magnetic semiconductor; p; -Type doping; Room-temperature ferromagnetism

Current–voltage characterization of Au contact on sol–gel ZnO films with and without conducting polymer by Yow-Jon Lin; Mei-Jyuan Jheng; Jian-Jhou Zeng (pp. 4493-4496).

This study investigates the current density–voltage ( J– V) characteristics of Au/n-type ZnO and Au/polyaniline (PANI)/n-type ZnO devices. ZnO films were prepared by the sol–gel method. For Au/n-type ZnO devices, native defects and impurities resident within the ZnO depletion region contribute to barrier thinning of, carrier hopping across, and tunneling through the Schottky barrier. This leads to the formation of nonalloyed ohmic contacts. However, rectifying junctions were formed on n-type ZnO by employing the simple technique of spin-coating PANI to act as the electron-blocking layer. Our present results suggest that the ZnO depletion region at the PANI/n-type ZnO interface is not the origin of the rectifying behavior of Au/PANI/n-type ZnO contact. In addition, the presence of the built-in potential of Au/PANI/n-type ZnO devices could result in the shift of the J– V curve toward negative voltage. Excellent agreement between simulated and measured data was obtained when the built-in potential was taken into account in the J– V relationship.

Keywords: Zinc oxide; Schottky emission; Oxides; Polymer

Preparation, characterization and properties of novel covalently surface-functionalized zinc oxide nanoparticles by Moriyuki Sato; Hajime Harada; Shigekazu Morito; Yasuhisa Fujita; Shunsuke Shimosaki; Takeshi Urano; Morihiko Nakamura (pp. 4497-4501).

Novel covalently surface-modified zinc oxide (ZnO) nanoparticles (NP) (ZHIE) were successfully prepared, which have organic chains composed of hydrophilic amide and urethane linkages, and terminal amino groups on the surfaces, using zinc acetate monohydrate. FTIR spectroscopy, X-ray analysis and TEM observation suggested that the resultant ZHIE NPs have the mean sizes of about 10nm in diameters, the organic chains linking the amino groups in the terminals and wurtzite crystal structure. UV–vis absorption spectrum of the ZHIE NPs in methanol showed maximum absorption band at 348nm, supporting the TEM observations. Photoluminescent spectrum measurements depicted that the ZHIE NPs show broad visible emission band on the basis of trapped-electron emission. Cytotoxicity and phagocytosis assays suggested that the ZHIE NPs are noncytotoxic, and the ZHIE-labeled zymosan particles derived by conjugation of the ZHIE NPs with zymosan are internalized into the cells and generate fluorescence based on the ZHIE NPs.

Keywords: Surface functionalization; Zinc oxide nanoparticle; UV–vis absorption; Visible emission; Noncytotoxicity

Dependence of surface nano-structural modifications of Ti implanted by N⁺ ions on temperature by Masoumeh Firouzi-Arani; Hadi Savaloni; Mahmood Ghoranneviss (pp. 4502-4511).

The surface modification of titanium thin foil/sheet samples (0.5mm) implanted by nitrogen ions of 30 keV energy and a fluence of 1×10¹⁸N⁺cm⁻² at different temperatures is studied using XRD, AFM, SEM, and SIMS. XRD patterns showed the development of titanium nitride with different compositions in the implanted samples, while the presence of different titanium compositions such as titanium oxides was also observed. AFM images at 654K showed the formation of grains, that after initial sputtering of the grain boundary at 728K temperature, the morphology of the surface changed from small grains to a bimodal distribution of grains at 793K which consisted of larger grains with bright hillocks within them. This was considered to be due to phase transformation/compositional changes, explained by correlating XRD and SIMS results. The SIMS results showed a maximum at about 730K and a minimum at about 790K for both N⁺ density and depth of N⁺ penetration in the Ti sample. The variation of these results with temperature was explained on the basis of the residual gas, substrate temperature, dissociation of water in the chamber and the gettering property of titanium.

Keywords: PACS; 68.55.Ln; 68.49.Sf; 82.80.Ms; 68.37.PsSEM; AFM; XRD; SIMS; Ion implantation; Depth profile; Ion implantation

Elastic–plastic analyses on the residual stresses and curvature of the film/substrate bilayer system by X.C. Zhang; F.Z. Xuan; Z.D. Wang; S.T. Tu (pp. 4512-4516).

During thermal cycling, the residual stresses are often generated in the film/substrate bilayer due to the material mismatch between the substrate and the film. If the thickness of the film is relatively high, the thermal residual stresses in it may be of different signs. When the film is subjected to elastic–plastic deformation, two plastic zones with different thicknesses may be generated in the film at a significantly high temperature difference. In this paper, a theoretical model which reflects the complete history of thermal residual stresses and curvatures in the elastoplastic film/substrate bilayer system is developed. Solutions are derived to estimate the residual stresses and curvature in the film as functions of temperature difference. The case of Al/Si system is used to illustrate the implementation of this model. Results show that the critical temperature difference at which the second plastic zone near the film surface is generated near the Al film surface is dependent on the film thickness. The strain hardening of the film has an obvious influence on the magnitude of residual stresses within the film at high temperature difference.

Keywords: Film/substrate system; Residual stress; Curvature; Elastic–plastic analyses

Carbon monoxide adsorption on Co deposited Pt(100)-hex: IRRAS and LEED investigations by T. Wadayama; H. Yoshida; K. Ogawa; N. Todoroki; Y. Yamada (pp. 4517-4521).

Infrared reflection absorption spectroscopy (IRRAS) was used to investigate carbon monoxide (CO) adsorption on Pt(100) surfaces deposited with Co layers with different thicknesses. Pt(100) surfaces cleaned in ultrahigh vacuum showed surface reconstruction, i.e., Pt(100)-hex: two absorption bands ascribable to adsorbed CO on the 1×1 surface and hex domains emerge at 2086 and 2074cm⁻¹, respectively, after 1.0L CO exposure. Deposition of a 0.3-nm-thick-Co layer on Pt(100)-hex at 333K changes the low-energy electron diffraction (LEED) pattern from hex to p(1×1), indicating that the deposited Co lifts the reconstruction. The IRRAS spectrum for 1.0-L-CO-exposed Co0.3_nm/Pt(100)-hex fabricated at 333K yields a single absorption band at 2059cm⁻¹. For Co0.3_nm/Pt(100)-hex fabricated at 693K, the LEED pattern shows a less-contrasted hex and the pattern remains nearly unchanged even after CO exposure of 11L, although only 1.0L CO exposure to Pt(100)-hex lifts the surface reconstruction. A Co0.3_nm/Pt(100)-hex surface fabricated at 753K exhibits an absorption band at 2077cm⁻¹, which is considered to originate from CO adsorbed on the Pt-enriched surface alloy. Co0.3_nm/Pt(100)-hex surfaces fabricated above 773K show a clear hex-reconstructed LEED pattern, and the frequencies of the adsorbed CO bands are comparable to those of Pt(100)-hex, indicating that the deposited Co atoms are diffused near the surface region. The outermost surface of the 3.0-nm-thick-Co-deposited Pt(100)-hex is composed of Pt–Co alloy domains even at a deposition temperature of 873K. Based on the LEED and IRRAS results, the outermost surface structures of Co_x/Pt(100)-hex are discussed.

Keywords: Infrared absorption spectroscopy; Low-energy electron diffraction; Carbon monoxide; Platinum; Cobalt; Hex reconstruction; Surface alloy

Comparison of surface films formed on titanium by pulsed Nd:YAG laser irradiation at different powers and wavelengths in nitrogen atmosphere by Naofumi Ohtsu; Kenji Kodama; Kuniyuki Kitagawa; Kazuaki Wagatsuma (pp. 4522-4526).

The nitridation of titanium (Ti) caused by a Q-switched Nd:YAG laser under nitrogen gas atmosphere was investigated in situ using X-ray photoelectron spectroscopy (XPS). A laser having a wavelength of 1064nm and 532nm (SHG mode) was irradiated on a titanium substrate in an atmosphere-controlled chamber, and the substrate was then transported to an XPS analysis chamber without exposing it to air. The characteristics of the surface layer strongly depend on the laser power. When the power is relatively low, a titanium dioxide layer containing a small amount of nitrogen is formed on the substrate. Laser irradiation beyond a certain laser power is required to obtain a stoichiometric titanium nitride (TiN) layer. A TiN layer and an oxynitride layer with a TiO_xN_y-like structure are formed as the topmost and the lower surface layer, respectively, when the laser power exceeds this threshold value. The threshold laser power strongly depends on the wavelength of the laser, and this threshold value for the 532-nm laser is quite lower than that for the 1064-nm laser.

Keywords: Laser nitridation; In situ; XPS; Laser power and wavelength; Titanium nitride

Effects of atomic oxygen treatment on structures, morphologies and electrical properties of ZnO:Al films by Wenwen Wang; Chunzhi Li; Junying Zhang; Xungang Diao (pp. 4527-4532).

ZnO:Al (ZAO) film has a potential application in providing spacecrafts the protection against atomic oxygen (AO) erosion. To advance the understanding of the AO resisting mechanisms and the relationships between the structures, morphologies and conductive properties of ZAO film, direct current magnetron sputtered ZAO films with different thicknesses were treated with AO in a ground-based simulation facility. The microstructure, surface chemical state, morphologies and electrical properties of pristine films and irradiated ones were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and Hall measurement. It is found that AO exposure produces novel, oriented recrystallization of the surface particles. It also increases the content of oxygen ions in fully oxidized stoichiometric surroundings on the surface, resulting in the decrease of the conductivity. As the thickness of ZAO film increases, the crystallinity, conductivity and resistance to AO erosion are all improved.

Keywords: ZnO:Al film; Atomic oxygen; Surface structure; Morphologies; Electrical properties

Improved performance of TiO₂ electrodes coated with NiO by magnetron sputtering for dye-sensitized solar cells by Li Li; Renjie Chen; Ge Jing; Guiyou Zhang; Feng Wu; Shi Chen (pp. 4533-4537).

TiO₂ electrodes are coated with NiO by DC magnetron sputtering, and their structural, optical and electrochemical performance has been investigated. X-ray diffractometry (XRD), UV–vis spectrophotometry, scanning electron microscopy (SEM), AC impedance, and linear sweep voltammetry (LSV) are used to characterize the TiO₂/NiO electrodes. Their performance is evaluated with a computer controlled electrochemical workstation in combination with three conventional electrodes. The experimental results indicate that the surface modification of TiO₂ electrodes with sputtered NiO reduces trap sites on TiO₂ and improves the electrochemical performance of dye-sensitized solar cells (DSSCs). Sputtering NiO for 7min, which is about 21nm thick, on 6.5μm thick TiO₂ greatly improves the DSSC parameters, and the conversion efficiency increases from 3.21 to 4.16%. Mechanisms of the influence of the NiO coating on electrochemical performance are discussed.

Keywords: Dye-sensitized solar cells; Titanium dioxide electrodes; Nickel oxide coating; Magnetron sputtering

Influence of the heating temperature on the properties of nickel doped TiO₂ films prepared by sol–gel method by V. Kisand; U. Joost; V. Reedo; R. Pärna; T. Tätte; J. Shulga; A. Saar; L. Matisen; A. Kikas; I. Kink (pp. 4538-4542).

Formation and properties of nickel doped TiO₂ films prepared by sol–gel method were studied using X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, and energy dispersive X-ray analysis. The results demonstrate that sizes of TiO₂ crystallites increase with increasing heating temperature. Also, at temperatures above 800° C diffusion of nickel onto the surfaces results in increased concentrations of nickel compounds on the surfaces. Similar to pure TiO₂ films the light-induced modification of hydrophilicity is observed also in the case of nickel doped TiO₂ films.

Keywords: Titanium oxide; Nickel; Sol–gel films; XPS

Effect of aging time of ZnO sol on the structural and optical properties of ZnO thin films prepared by sol–gel method by Yaoming Li; Linhua Xu; Xiangyin Li; Xingquan Shen; Ailing Wang (pp. 4543-4547).

In this work, ZnO thin films were prepared by sol–gel method and the effect of aging time of ZnO sol on the structural and optical properties of the films was studied. The structural characteristics of the samples were analyzed by an atomic force microscope and an X-ray diffractometer. The optical properties were studied by a UV–vis spectrophotometer and a fluorophotometer. The results show that the ZnO thin film prepared by the as-synthesized ZnO sol had relatively poor crystalline quality, low optical transmittance in the visible range and relatively weak ultraviolet emission performance. After the as-synthesized ZnO sol was aged for 24h, the degree of the preferred crystal orientation along the c-axis of the ZnO thin film prepared by this aged sol was improved. At the same time, this film had a very smooth surface with uniform grains and both its visible range transmittance and ultraviolet emission intensity were obviously increased. These results suggest that appropriate aging of ZnO sol is very important for the improvement of structural and optical quality of ZnO thin films derived from sol–gel method.

Keywords: PACS; 61.10.Nz; 68.37.Ps; 68.55.−a; 73.61.Ga; 74.25.GzZnO thin films; Sol–gel method; Aging time; Transmittance; Photoluminescence

SiO_xN_y thin films with variable refraction index: Microstructural, chemical and mechanical properties by V. Godinho; M.C. Jiménez de Haro; J. García-López; V. Goossens; H. Terryn; M.P. Delplancke-Ogletree; A. Fernandez (pp. 4548-4553).

In this work amorphous silicon oxynitride films with similar composition (ca. Si_0.40N_0.45O_0.10) were deposited by reactive magnetron sputtering from a pure Si target under different N₂–Ar mixtures. Rutherford backscattering (RBS) studies revealed that the coatings presented similar composition but different density. The mechanical properties evaluated by nanoindentation show also a dependence on the deposition conditions that does not correlate with a change in composition. An increase in nitrogen content in the gas phase results in a decrease of hardness and Young's modulus.The microstructural study by high resolution scanning electron microscopy (SEM-FEG) on non-metalized samples allowed the detection of a close porosity in the form of nano-voids (3–15nm in size), particularly in the coatings prepared under pure N₂ gas. It has been shown how the presence of the close porosity allows tuning the refraction index of the films in a wide range of values without modifying significantly the chemical, thermal and mechanical stability of the film.

Keywords: Silicon oxynitride; Nanostructured coatings; Tailored refraction index; Nanoindentation; Nano-voids

Rubbing effect on surface morphology and thermoelectric properties of TTF–TCNQ thin films by E. Tamayo; K. Hayashi; T. Shinano; Y. Miyazaki; T. Kajitani (pp. 4554-4558).

Thin films of tetrathiofulvalene–tetracyanoquinodimethane (TTF–TCNQ), a typical organic material of charge transfer salts, were prepared on glass substrates by evaporation using TTF–TCNQ powder. The rubbing effect on the surface morphology and thermoelectric properties was studied. TTF–TCNQ films exhibited a bush-like disordered growth on the as-received glass substrate, whereas those on the rubbed glass substrate had extremely flat surfaces tiled with small rectangular TTF–TCNQ single crystals. Due to the ordered alignment of TTF–TCNQ tiles, improvement in the electrical conductivity and enhancement of the Seebeck coefficient were achieved.

Keywords: Organic thin film; TTF–TCNQ; Thermoelectric conversion; Rubbing technique

Characterization of the surface and the interphase of PVC–copper amine-treated wood composites by Haihong Jiang; D. Pascal Kamdem (pp. 4559-4563).

Contact angles and surface energy of wood, as well as interfacial shear strength between wood and polyvinyl chloride (PVC) were investigated and used to monitor the modifications generated on the surfaces of wood treated with a copper ethanolamine solution. An increase in surface energy of wood after treatments promotes wetting of PVC on wood surfaces. Improved interfacial shear strength between treated wood and PVC matrix can be attributed to the formation of a stronger wood–PVC interphase. This suggests that treatment may be used to improve the adhesion between wood surface and PVC in the formulation of wood fiber composites to yield products with enhanced mechanical properties and better biological and physical performance against decay and insect destroying wood.

Keywords: PVC; Interfacial shear; Copper amine; Wood composites; Surface energy; Contact angle

The impact of annealing temperature and time on the electrical performance of Ti/Pt thin films by M. Grosser; U. Schmid (pp. 4564-4569).

In this study, we focus on the influence of annealing time t_PDA (i.e. 30min and 630min) on the room-temperature resistivity of electron-beam-evaporated titanium/platinum thin films when exposed to thermal loads up to temperatures T_PDA of 700°C. The titanium has a fixed thickness of 5nm and serves as an adhesion layer. The thickness d f_,Pt of the platinum top layer is varied between 21 and 97nm. Up to annealing temperatures of 450°C, the film resistivity of the bi-layer system is linearly correlated with the reciprocal platinum film thickness independent of t_PDA, as expected from the size effect. At t_PDA=30min, the change in intrinsic film stress dominates the electrical behavior in this annealing regime, predominantly at large d f_,Pt values. Compared to t_PDA=630min, however, the increase in resistivity especially at low platinum film thickness is substantially larger demonstrating that titanium starts to diffuse at these long annealing times even at moderate temperatures. At T_PDA=600°C, the diffusion of titanium into the top layer leads to an enhanced increase in film resistivity ρ_f, especially at low platinum thicknesses and low annealing times, as the mean penetration depth of diffused titanium is under these conditions in order of d f_,Pt. Above T_PDA=600°C, ρ_f is slightly increased at t_PDA=30min. At t_PDA=630min, however, the film resistivity is decreased at d f_,Pt<58nm. This is attributed to grain growth and re-crystallization effects. Furthermore, the mean penetration depths of titanium substantially exceed d f_,Pt resulting predominantly in Ti_xO_y formation on the top film surface and hence, having low impact on ρ_f.

Keywords: Platinum; Thin film; Resistivity; High-temperature annealing; Diffusion

Surface characterization of acidic ceria–zirconia prepared by direct sulfation by B. Azambre; L. Zenboury; J.V. Weber; P. Burg (pp. 4570-4581).

Acidic ceria–zirconia (SCZ) solid acid catalysts with a nominal surface density of ca 2 SO₄²⁻/nm² were prepared by a simple route consisting in soaking high specific surface area Ce_xZr1−_xO₂ (with x=0.21 and 0.69) mixed oxides solutions in 0.5M sulphuric acid. Characterizations by TPD-MS, TP-DRIFTS and FT-Raman revealed that most of surface structures generated by sulfation are stable at least up to 700°C under inert atmosphere and consist mainly as isolated sulfates located on defects or crystal planes and to a lesser extent as polysulfates. Investigations by pyridine adsorption/desorption have stated that: SCZ possess both strong Brønsted (B) and Lewis (L) acid sites, some of them being presumably superacidic; the B/L site ratio was found to be more dependent on the temperature and hydration degree than on the composition of the ceria–zirconia. By contrast, the reactivity of the parent Ce_xZr1−_xO₂ materials towards pyridine is mostly driven by redox properties resulting in the formation of Py-oxide with the participation of Lewis acid sites of moderate strength ( cus Ce x⁺ and Zr x⁺ cations). Basicity studies by CO₂ adsorption/desorption reveal that SCZ surfaces are solely acidic whereas the number and strength of Lewis basic sites increases with the Ce content for the parent Ce_xZr1−_xO₂ materials.

Keywords: DRIFTS; Pyridine adsorption; Sulfated ceria–zirconia; Acidity; TPD

Adhesion and stress of magnesium oxide thin films: Effect of thickness, oxidation temperature and duration by Sikandar H. Tamboli; Vijaya Puri; R.K. Puri (pp. 4582-4585).

Nanoscale magnesium oxide thin films have been deposited on glass substrate by thermal oxidation (in air) of vacuum evaporated magnesium films. X-ray diffraction (XRD) showed orientation along (200) and (220) directions. The mechanical properties of the MgO thin films were found to be the function of thickness (300, 450 and 600nm), oxidation temperature (573, 623 and 673K) and oxidation duration (90 and 180min). As oxidation temperature and oxidation duration increases, adhesion and intrinsic stress were found to increase. Intrinsic stress decreased whereas adhesion increased due to increase in thin film thickness. The value of intrinsic stress was in range 28.902–73.212 (×10⁷N/m²) and that of adhesion was 12.1–27.4 (×10⁴N/m²) for the thin film of thickness 300nm.

Keywords: Thin films; Oxide materials; Vapour deposition; Adhesion; Intrinsic stress

The influence of polymer concentrations on the structure and mechanical properties of porous polycaprolactone-coated hydroxyapatite scaffolds by J. Zhao; K. Duan; J.W. Zhang; X. Lu; J. Weng (pp. 4586-4590).

Polycaprolactone (PCL)-coated porous hydroxyapatite (HA) composite scaffolds were prepared by combining polymer impregnating method with dip-coating method. Three different PCL solution concentrations were used in dip-coating process to improve the mechanical properties of porous HA scaffolds. The results indicated that as the concentration of PCL solution increases the compressive strength significantly increased from 0.09MPa to 0.51MPa while the porosity decreased from 90% to 75% for the composite scaffolds. An interlaced structure was found inside the pore wall for all composite scaffolds due to the penetration of PCL. The porous HA/PCL composite scaffolds dip-coated with 10% PCL exhibited optimal combination of mechanical properties and pore interconnectivity, and may be a potential bone candidate for the tissue engineering applications.

Keywords: Porous scaffold; Hydroxyapatite; Composite; Polymer coating; Mechanical properties

Structural and optical properties of a-Si1−_xC_x:H films synthesized by dc magnetron sputtering technique by Aïssa Keffous; Abdelhak Cheriet; Youcef Belkacem; Noureddine Gabouze; Assia Boukezzata; Yacine Boukennous; Amer Brighet; Rabah Cherfi; Mohamed Kechouane; Lakhdar Guerbous; Isa Menous; Hamid Menari (pp. 4591-4595).

Hydrogenated amorphous SiC films (a-Si1−_xC_x:H) were prepared by dc magnetron sputtering technique on p-type Si(100) and corning 9075 substrates at low temperature, by using 32 sprigs of silicon carbide (6H–SiC). The deposited a-Si1−_xC_x:H film was realized under a mixture of argon and hydrogen gases. The a-Si1−_xC_x:H films have been investigated by scanning electronic microscopy equipped with an EDS system (SEM-EDS), X-ray diffraction (XRD), secondary ions mass spectrometry (SIMS), Fourier transform infrared spectroscopy (FTIR), UV–vis–IR spectrophotometry, and photoluminescence (PL). XRD results showed that the deposited film was amorphous with a structure as a-Si_0.80C_0.20:H corresponding to 20at.% carbon. The photoluminescence response of the samples was observed in the visible range at room temperature with two peaks centred at 463nm (2.68eV) and 542nm (2.29eV). In addition, the dependence of photoluminescence behaviour on film thickness for a certain carbon composition in hydrogenated amorphous SiC films (a-Si1−_xC_x:H) has been investigated.

Keywords: PACS; 71.20.Nr; 78.20.−e; 78.40.−q; 78.55.−mSilicon carbide; Sputtering; Amorphous film; Structure; Luminescence; SIMS

Immobilization of cholesterol oxidase to finely dispersed silica-coated maghemite nanoparticles based magnetic fluid by Franja Šulek; Željko Knez; Maja Habulin (pp. 4596-4600).

In the recent years, the potential applicability of magnetic nanoparticles (MNPs) has witnessed a significant increase in interest towards the medical field, in particular, towards the usage of novel nanoparticles in diagnostics and disease treatment, respectively. In a present study, cholesterol oxidase (ChOx) was covalently immobilized to magnetic nanoparticles of maghemite (γ-Fe₂O₃) and further functionalized by silica (SiO₂) and amino-silane molecules. The activity of the bound enzyme was retained up to 60%, respectively. The binding of cholesterol oxidase was confirmed using FT-IR spectrophotometer. SEM analysis showed uniformly dispersed functional magnetic nanoparticles, which ranged in size from 22.5 to 50.8nm, surrounded by amorphous silica. In this paper, the potential applications of chemically modified magnetic nanoparticles as carriers for cholesterol oxidase and other enzymes are discussed.

Keywords: Abbreviations; AEAPS; 3-(2-aminoethylamino)-propyl-dimethoxymethylsilane; ChOx; cholesterol oxidase; FT-IR; Fourier transform infrared spectroscopy; E; designation for enzyme; MNPs; magnetic nanoparticles; PBS; phosphate buffer solution; BSA; bovine serum albuminMagnetic nanoparticles; Magnetic carrier; Enzyme immobilization; Cholesterol oxidase

Oxygen influence on sputtered high rate ZnO:Al films from dual rotatable ceramic targets by H. Zhu; J. Hüpkes; E. Bunte; S.M. Huang (pp. 4601-4605).

In this study, the influence of oxygen on high rate (up to 110nmm/min) sputtered aluminum doped zinc oxide films (ZnO:Al) was systematically investigated. Different oxygen gas flows from 0sccm to 8sccm were inputted into the chamber during the preparation of ZnO:Al films from dual rotatable ceramic targets under high discharge power (14kW). The resistivity increases from 4.2×10⁻⁴Ωcm to 4.3×10⁻²Ωcm with the rising oxygen gas flow. While both the carrier concentration and mobility drop by one order of magnitude from 3.4×10²⁰cm⁻³ to 2.5×10¹⁹cm⁻³ and from 43.5cm²/Vs to 5.6cm²/Vs, respectively. The as-grown ZnO:Al films and after-etched ZnO:Al films after a chemical wet etching step in diluted HCl solution (0.5%) exhibit different surface structures. All films show high light transmission and low light absorption but different light scattering properties (diffusion and haze) because of different surface structures. Moreover, ZnO:Al films display different optical bandgaps between 3.51eV and 3.27eV, which are corresponding to different carrier concentrations. The variation of mobility and morphology is related with chemisorption of oxygen in the grain boundaries as well as high energetic oxygen ions bombardment.

Keywords: ZnO:Al films; Ceramic targets; Sputtering; Surface structures

Structure evolution and stoichiometry control of Pb(Zr, Ti)O₃ thick films fabricated by electrospray assisted vapour deposition by Jing Du; Yiquan Wu; Kwang-Leong Choy; Philip H. Shipway (pp. 4606-4611).

Well-crystallized and stoichiometric Pb(Zr, Ti)O₃ (PZT) films, typically ∼5μm thick, with pure perovskite-type rhombohedral structures have been successfully prepared via an electrospray assisted vapour deposition (ESAVD) method. Control of the deposition temperature within a narrow range of 300–400°C resulted in films with the most desirable phases. PZT films with close stoichiometric match with the expected composition ratio and uniform element distribution were obtained by adding the appropriate levels of excess Pb in the precursor solutions. The annealed films were uniform, dense, compact and adherent to the substrates. The dielectric constant, ɛ_r, and loss tangent, tan δ, of the fabricated PZT films measured at 10kHz were 442 and 0.09, respectively. The ESAVD deposited PZT films showed a remanent polarization, P_r, of 15.3μC/cm² and coercive field, E_c, of 86.7kV/cm. These results demonstrate the clear potential of the ESAVD method as a promising technique for the fabrication of thick PZT films.

Keywords: Pb(Zr, Ti)O; ₃; Electrospray assisted vapour deposition; Thick films

Mechanics and energy analysis on molten pool spreading during laser solid forming by Jun Yu; Xin Lin; Junjie Wang; Jing Chen; Weidong Huang (pp. 4612-4620).

This paper studies the issue that the molten pool width gradually increases under some conditions during laser solid forming (LSF), which can decrease the shape and dimension accuracy of LSFed component to a large extent. By using the statics analysis method and calculating the interfacial tensions at the solid–liquid–gas triple point of molten pool, the proposed two-dimensional (2D) cross-sectional model of single deposition layer illustrates qualitatively that the deposition width would increase with the increasing pool temperature at a certain powder feeding rate, which we called the pool spread behavior here. Meanwhile, by calculating the maximum equilibrium contact angle for keeping solid–liquid–gas triple point balance, it is found that the molten pool is solidified during non-equilibrium state. Furthermore, in order to control the pool temperature and decrease pool spread amount, the optimal match of pool energy and mass inputs is determined for obtaining an optimum balance between the energy input and deposition efficiencies.

Keywords: Laser solid forming; Molten pool spreading; Interfacial tensions; AISI-304 stainless steel

Characterization and properties of ZnO1−_xS_x alloy films fabricated by radio-frequency magnetron sputtering by H.L. Pan; T. Yang; B. Yao; R. Deng; R.Y. Sui; L.L. Gao; D.Z. Shen (pp. 4621-4625).

A series of ZnO1−_xS_x alloy films (0≤ x≤1) were grown on quartz substrates by radio-frequency (rf) magnetron sputtering of ZnS ceramic target, using oxygen and argon as working gas. X-ray diffraction measurement shows that the ZnO1−_xS_x films have wurtzite structure with (002) preferential orientation in O-rich side (0≤ x≤0.23) and zinc blende structure with (111) preferential orientation in S-rich side (0.77≤ x≤1). However, when the S content is in the range of 0.23< x<0.77, the ZnO1−_xS_x film consists of two phases of wurtzite and zinc blende or amorphous ZnO1−_xS_x phase. The band gap energy of the films shows non-linear dependence on the S content, with an optical bowing parameter of about 2.9eV. The photoluminescence (PL) measurement reveals that the PL spectrum of the wurtzite ZnO1−_xS_x is dominated by visible band and its PL intensity and intensity ratio of UV to visible band decrease greatly compared with undoped ZnO. All as-grown ZnO1−_xS_x films behave insulating, but show n-type conductivity for w-ZnO1−_xS_x and maintain insulating properties for β-ZnO1−_xS_x after annealed. Mechanisms of effects of S on optical and electrical properties of the ZnO1−_xS_x alloy are discussed in the present work.

Keywords: Rf-magnetron sputtering; ZnO; 1−; _x; S; _x; alloy films; Crystal structure; Optical and electrical properties

Composition, morphology and surface recombination rate of HCl–isopropanol treated and vacuum annealed InAs(111)A surfaces by V.G. Kesler; V.A. Seleznev; A.P. Kovchavtsev; A.A. Guzev (pp. 4626-4632).

X-ray photoelectron spectroscopy and atomic force microscopy were used to examine the chemical composition and surface morphology of InAs(111)A surface chemically etched in isopropanol–hydrochloric acid solution (HCl–iPA) and subsequently annealed in vacuum in the temperature range 200–500°C. Etching for 2–30min resulted in the formation of “pits” and “hillocks” on the sample surface, respectively 1–2nm deep and high, with lateral dimensions 50–100nm. The observed local formations, whose density was up to 3×10⁸cm⁻², entirely vanished from the surface after the samples were vacuum-annealed at temperatures above 300°C. Using a direct method, electron beam microanalysis, we have determined that the defects of the hillock type includes oxygen and excessive As, while the “pits” proved to be identical in their chemical composition to InAs. Vacuum anneals were found to cause a decrease in As surface concentration relative to In on InAs surface, with a concomitant rise of surface recombination rate.

Keywords: Etching; Annealing; InAs; XPS; AFM

Comparison of the laser ablation process on Zn and Ti using pulsed digital holographic interferometry by E. Amer; P. Gren; A.F.H. Kaplan; M. Sjödahl; M. El Shaer (pp. 4633-4641).

Pulsed digital holographic interferometry has been used to compare the laser ablation process of a Q-switched Nd-YAG laser pulse (wavelength 1064nm, pulse duration 12ns) on two different metals (Zn and Ti) under atmospheric air pressure. Digital holograms were recorded for different time delays using collimated laser light (532nm) passed through the volume along the target. Numerical data of the integrated refractive index field were calculated and presented as phase maps. Intensity maps were calculated from the recorded digital holograms and are used to calculate the attenuation of the probing laser beam by the ablated plume. The different structures of the plume, namely streaks normal to the surface for Zn in contrast to absorbing regions for Ti, indicates that different mechanisms of laser ablation could happen for different metals for the same laser settings and surrounding gas. At a laser fluence of 5J/cm², phase explosion appears to be the ablation mechanism in case of Zn, while for Ti normal vaporization seems to be the dominant mechanism.

Keywords: Laser ablation; Metals; Pulsed digital holographic interferometry

A comparative study of field emission properties of carbon nanotube films prepared by vacuum filtration and screen-printing by Min Qian; Tao Feng; Kai Wang; Hui Ding; Yiwei Chen; Zhuo Sun (pp. 4642-4646).

A comprehensive comparative study of electron field emission properties of carbon nanotube (CNT) films prepared by vacuum filtration and screen-printing was carried out. Field emission performance of vacuum filtered CNT films with different filtered CNT suspension volumes was systematically studied, and the optimum electron emission was obtained with a low turn on field of ∼0.93V/μm (at 1μA/cm²) and a high field enhancement factor β of ∼9720. Comparing with screen-printed CNT films, vacuum filtered CNT films showed better electron emission performance, longer lifetime, and greater adhesive strength to substrates. This work reveals a potential use of vacuum filtered CNT films as field emission cathodes.

Keywords: PACS; 79.70.+qCarbon nanotube; Field emission; Vacuum filtration; Screen-printing

Influence of hydrogen bonds and double bonds on the alkane and alkene derivatives self-assembled monolayers on HOPG surface: STM observation and computer simulation by Xinrui Miao; Chumin Chen; Jian Zhou; Wenli Deng (pp. 4647-4655).

The adsorption structure and hydrogen-bonded complexes of alkane and alkene derivatives self-assembled on HOPG were studied by scanning tunneling microscopy (STM) and Molecular Mechanics (MM) simulations. The effect of different interior –CHCH– conformations and functional groups in molecules on the structure and stability of self-assembled monolayers was considered. It was found that octadecanol and trans-oleic acid could form stable structure on HOPG and their high-resolution images could be obtained by STM. Octadecanol exhibited two kinds of packing by alkyl–alkyl and adsorbate–substrate interactions. The interior trans–CHCH– group in trans-oleic acid had a slight influence on the self-assembly configuration. However, owing to the cis-double bond in the interior of cis-oleyamine molecule, the ordered monolayer could not be easily imaged by STM at ambient conditions. The adsorption conformations of three kinds of molecules on HOPG surface were optimized by MM simulation, respectively. The analysis of hydrogen-bond interactions by computation stimulation also revealed that the stability of cis-oleyamine on HOPG was the worst. These results demonstrated that molecular self-assembly and its stability could be significantly tailored by changing the molecular structure.

Keywords: PACS; 07.79.Fc; 33.80.−b; 87.15.nr; 33.15.FmSelf-assembly; Scanning tunneling microscopy (STM); Hydrogen bonding; Alkane and alkene derivatives; Computer simulation; Structure and stability

Optimization of laser patterning of textured gallium-doped zinc oxide for amorphous silicon photovoltaics by Q. Qiao; K. Ma; Y.Q. Wang; G.C. Zhang; Z.R. Shi; G.H. Li (pp. 4656-4660).

Laser scribing process of in-house textured gallium-doped zinc oxide (GZO) is optimized, aiming to improve the performance of amorphous silicon (a-Si:H) photovoltaic (PV) modules. The reasons for different scribing quality of textured GZO and SnO₂:F scribed at 1064nm with pulse duration of 40ns were analyzed. Apart from separation resistance, quality of the scribed lines was evaluated by laser scan microscopy from three-dimensional images. Other types of lasers, such as laser with shorter pulse duration, laser at 355nm and laser with Gaussian-to-tophat converter, were used to smooth the edges and flatten the bottoms of the scribed lines. The proper laser scribing realizes the advantages of textured GZO films used as front contacts in PV modules. A short-circuit current density of 14.3mA/cm² and an initial aperture area efficiency of 8.8% were obtained on 16cm×16cm textured GZO coated glass scribed at 355nm with pulse duration of 40ns.

Keywords: Amorphous silicon photovoltaics; Laser scribing; Gallium-doped zinc oxide

Spectroscopic characterization approach to study surfactants effect on ZnO₂ nanoparticles synthesis by laser ablation process by Q.A. Drmosh; M.A. Gondal; Z.H. Yamani; T.A. Saleh (pp. 4661-4666).

Zinc peroxide nanoparticles having grain size less than 5nm were synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3% H₂O₂. The effect of surfactants on the optical and structure of ZnO₂ was studied by applying different spectroscopic techniques. Structural properties and grain size of the synthesized nanoparticles were studied using XRD method. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7, 3.7, 3.3 and 2.8nm in pure H₂O₂, and H₂O₂ mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO₂ nanoparticles prepared with and without surfactants show a characteristic ZnO₂ absorption at 435–445cm⁻¹. FTIR spectrum revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM while it appears in case of SDS. This could be due to high critical micelles SDS concentration comparing with others which is attributed to the adsorption anionic nature of this surfactant. Both FTIR and UV–vis spectra show a red shift in the presence of SDS and blue shift in the presence of CTAB and OGM. The blue shift in the absorption edge indicates the quantum confinement property of nanoparticles. The zinc peroxide nanoparticles prepared in additives-free media was also characterized by Raman spectra which show the characteristic peaks at 830–840 and 420–440cm⁻¹.

Keywords: Zinc peroxide; Nanoparticles; Surfactants; Optical properties; Laser ablation

Size dependent 2p_3/2 binding-energy shift of Ni nanoclusters on SiO₂ support: Skin-depth local strain and quantum trapping by Yanguang Nie; Jisheng Pan; Zheng Zhang; Jianwei Chai; Shijie Wang; Chiam Sing Yang; Daniel Li; Chang Q. Sun (pp. 4667-4671).

An in situ X-ray photoelectron emission investigation revealed that the size trend of the 2p_3/2 binding-energy shift (BES) of Ni nanoclusters grown on SiO₂ substrate follows the prediction of the bond order–length–strength (BOLS) correlation theory . Theoretical reproduction of the measurements turns out that the 2p_3/2 binding energy of an isolated Ni atom is 850.51eV and its intrinsic bulk shift is 2.70eV. Findings confirmed that the skin-depth local strain and potential well quantum trapping induced by the shorter and stronger bonds between under-coordinated surface atoms provide perturbation to the Hamiltonian and hence dominate the size dependent BES.

Keywords: Nanostructures; Ni; Surface core level shift

Humidity effect on the interaction between carbon nanotubes and graphite by David Chabrier; Bharat Bhushan; Sophie Marsaudon (pp. 4672-4676).

An atomic force microscope is used to study the effect of humidity on the interaction between carbon nanotubes anchored to atomic force microscopy tips and various samples. Commercial silicon tips were also used for comparison. Adhesion force and dissipative energy were measured between these tips and highly oriented pyrolytic graphite (HOPG) and PMMA in contact mode. The data provides a detailed understanding of carbon nanotube interactions as a function of humidity.

Keywords: SWNT; MWNT; HOPG; Force curve

Excellent stability of plasma-sprayed bioactive Ca₃ZrSi₂O₉ ceramic coating on Ti–6Al–4V by Ying Liang; Youtao Xie; Heng Ji; Liping Huang; Xuebin Zheng (pp. 4677-4681).

In this work, novel zirconium incorporated Ca–Si based ceramic powder Ca₃ZrSi₂O₉ was synthesized. The aim of this study was to fabricate Ca₃ZrSi₂O₉ coating onto Ti–6Al–4V substrate using atmospheric plasma-spraying technology and to evaluate its potential applications in the fields of orthopedics and dentistry. The phase composition, surface morphologies of the coating were examined by XRD and SEM, which revealed that the Ca₃ZrSi₂O₉ coating was composed of grains around 100nm and amorphous phases. The bonding strength between the coating and the substrate was 28±4MPa, which is higher than that of traditional HA coating. The dissolution rate of the coating was assessed by monitoring the ions release and mass loss after immersion in the Tris–HCl buffer solution. The in vitro bioactivity of the coating was determined by observing the formation of apatite on its surface in simulated body fluids. It was found that the Ca₃ZrSi₂O₉ coating possessed both excellent chemical stability and good apatite-formation ability, suggesting its potential use as bone implants.

Keywords: Plasma spraying; Ca; ₃; ZrSi; ₂; O; ₉; Chemical stability; Apatite formation

Characterization of a-plane orientation ZnO film grown on GaN/Sapphire template by pulsed laser deposition by Xiangyun Han; Jiangnan Dai; Chenhui Yu; Zhihao Wu; Changqing Chen; Yihua Gao (pp. 4682-4686).

In this study, the authors have investigated the structural and optical properties of ZnO layer grown by pulsed laser deposition on GaN/ r-plane sapphire. X-ray diffraction results demonstrate the ZnO film to be highly preferentially deposited at a-axis orientation; the different rocking curve values along the two orthogonal directions indicate the low C2_v symmetry in the growth a-plane ZnO. From free stress to large tensile stress (about 1.34×10⁹Pa) distribution along the growth direction of ZnO is revealed by visible Raman mapping spectra. The enhanced significantly high-order longitudinal-optical (LO) phonon modes up to 4th and no TO phonons have been observed in Raman spectrum under UV 325nm by resonance conditions; an intense and broad disorder activated surface phonon mode is also observed, resulting from the increased disorder on the film surface with stripe-like growth features. Low-temperature photoluminescence measurements reveal that the band-edge emission of ZnO is dominated by neutral donor-bound exciton and free electrons to neutral acceptor emissions. Interfacial microstructure of ZnO/GaN has been examined by transmission electron microscopy, with the epitaxial relationship (101¯0) ZnO//(0002¯) GaN. All these results indicated that GaN template played an important role in the growth of ZnO film, with full advantage of small lattice mismatch.

Keywords: a; -Plane ZnO thin film; Pulsed laser deposition; X-ray diffraction; Raman scattering; Photoluminescence; Transmission electron microscopy

Micromould based laser shock embossing of thin metal sheets for MEMS applications by Huixia Liu; Zongbao Shen; Xiao Wang; Hejun Wang; Maoke Tao (pp. 4687-4691).

Laser shock forming is a new material processing technology. Micro-channel with dimension of 260μm×59μm was successfully fabricated on metallic foil surface using laser-generated shock wave. The work piece has a high spatial resolution at the micron-level. A series of experiments was conducted to validate the finite element model. An analysis procedure including dynamic analysis performed by ANSYS/LS-DYNA and static analysis performed by ANSYS is presented in detail to attain the simulation of laser shock embossing to predict the surface deformation. Micromould based laser shock embossing holds promise for achieving precise, well-controlled, low-cost, high efficiency of three-dimensional metallic microstructures. In addition, this technique can fabricate complex 3D microstructures directly by single pulse.

Keywords: Laser-generated shock wave; Mould based microforming; Laser shock embossing; Finite element method

Aligned synthesis of multi-walled carbon nanotubes with high purity by aerosol assisted chemical vapor deposition: Effect of water vapor by Hao Liu; Yong Zhang; Ruying Li; Xueliang Sun; Fengping Wang; Zhifeng Ding; Philippe Mérel; Sylvain Desilets (pp. 4692-4696).

Aligned multi-walled carbon nanotubes (MWCNTs) with high purity and bulk yield were achieved on a silicon substrate by an aerosol-assisted chemical vapor deposition. The introduction of specific amounts of water vapor played a key role in in situ controlling the purity and surface defects of the nanotubes. The morphology, surface quality and structure of MWCNTs were characterized by secondary and backscattered electron imaging in a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). Crystallinity and defects of the MWCNTs’ were investigated by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. In this work, water vapor was found to provide a weak oxidative environment, which enhanced and purified the MWCNTs’ growth. However, excessive water vapor would inhibit the MWCNTs growth with a poor surface quality. In addition, it has been found that the surface morphology of the CNTs can be modified intentionally through producing some surface defects by tuning the amount of the water vapor, which may offer more nucleation sites on the chemically inert CNT surface for various applications such as catalyst support.

Keywords: Catalysts; Chemical vapor deposition; Corrosion and oxidation; Nanomaterials

The wetting behaviour of silver on carbon, pure and carburized nickel, cobalt and molybdenum substrates by Robert C. Hula; Christian Edtmaier; Markus Holzweber; Herbert Hutter; Christoph Eisenmenger-Sittner (pp. 4697-4701).

Properties such as thermal and electrical conductivity or the expansion behaviour of silver matrix composites with carbon based inclusions are strongly affected by the contact angle between carbon and silver. In order to promote wetting of carbon, insertion of metallic interlayers such as nickel, cobalt or molybdenum is a feasible approach. This paper presents contact angle measurements done with the sessile drop method on carbon substrates (glassy carbon, polycrystalline graphite) and on pure nickel, cobalt and molybdenum foils. The ability of these interlayer elements to lower the high contact angles of silver on glassy carbon (117°) and polycrystalline graphite (124°) under vacuum conditions was verified. Unlike nickel (30°) and cobalt (26°), molybdenum (107°) nevertheless was not wettable by liquid silver (at 1273K) under vacuum conditions. ToF-SIMS was used to identify oxygen on the surface, causing higher contact angles than expected. After oxide reduction a contact angle of 18° on molybdenum was detected. Furthermore, the influence of carbon diffusion on the contact angle was investigated by gas phase carburization of the metal foils. ToF-SIMS and XRD identified dissolved carbon (Ni, Co) and carbide formation (Mo). However, only nickel and cobalt showed a slight decrease of the contact angle due to carbon uptake.

Keywords: Contact angle; Sessile drop method; Silver; Carbon; MMC; Interface thermal conductance

Preparation and optical properties of ZnGa₂O₄:Cr³⁺ thin films derived by sol–gel process by Weiwei Zhang; Junying Zhang; Yuan Li; Ziyu Chen; Tianmin Wang (pp. 4702-4707).

ZnGa₂O₄:Cr³⁺ thin films with bright red emission were synthesized using a sol–gel process, characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Auger electron spectroscopy (AES) and UV–vis and fluorescence spectrophotometry measurements. Effects of calcining temperature, film thickness, calcining duration and substrates on the crystal structure and photoluminescent property have been investigated. It is found that the crystallinity, Ga/Zn ratio and band gap energy ( E_g) are significant factors influencing optical characteristics, while the nature of substrates affect the surface morphologies of ZnGa₂O₄:Cr³⁺ thin films.

Keywords: ZnGa; ₂; O; ₄; :Cr; ³⁺; Photoluminescence; Thin film; Sol–gel process

Laser induction hybrid rapid cladding of WC particles reinforced NiCrBSi composite coatings by Shengfeng Zhou; Xiaoqin Dai (pp. 4708-4714).

In order to investigate the microstructure characteristics and properties of Ni-based WC composite coatings containing a relatively large amount of WC particles by laser induction hybrid rapid cladding (LIHRC) and compare to the individual laser cladding without preheating, Ni60A+35wt.% WC composite coatings are deposited on A3 steel plates by LIHRC and the individual laser cladding without preheating. The composite coating produced by the individual laser cladding without preheating exhibits many cracks and pores, while the smooth composite coating without cracks and pores is obtained by LIHRC. Moreover, the cast WC particles take on the similar dissolution characteristics in Ni60A+35wt.% WC composite coatings by LIHRC and the individual laser cladding without preheating. Namely, the completely dissolved WC particles interact with Ni-based alloy solvent to precipitate the blocky and herringbone carbides, while the partially dissolved WC particles still preserve the primary lamellar eutectic structure. A few WC particles are split at the interface of WC and W₂C, and then interact with Ni-based alloy solvent to precipitate the lamellar carbides. Compared with the individual laser cladding without preheating, LIHRC has the relatively lower temperature gradient and the relatively higher laser scanning speed. Therefore, LIHRC can produce the crack-free composite coating with relatively higher microhardness and relatively more homogeneous distribution of WC particles and is successfully applied to strengthen the corrugated roller, showing that LIHRC process has a higher efficiency and good cladding quality.

Keywords: Laser induction hybrid rapid cladding (LIHRC); Carbides; Cast WC particles; Individual laser cladding; Crack-free

CO₂ sensing properties of semiconducting copper oxide and spinel ferrite nanocomposite thin film by A. Chapelle; F. Oudrhiri-Hassani; L. Presmanes; A. Barnabé; Ph. Tailhades (pp. 4715-4719).

A new active layer for CO₂ sensing based on semiconducting CuO–Cu_xFe3−_xO₄ (with 0≤ x≤1) nanocomposite was prepared by radiofrequency sputtering from a delafossite CuFeO₂ target using a specific in situ reduction method followed by post annealing treatment in air. The tenorite–spinel ferrite nanocomposite layer was deposited on a simplified test device and the response in a carbon dioxide atmosphere was measured by varying the concentration up to 5000ppm, at different working temperatures (130–475°C) and frequencies (0.5–250kHz). The results showed a high response of 50% (Rair/RCO2=1.9) at 250°C and 700Hz for a CO₂ concentration of 5000ppm.

Keywords: Gas sensor; Carbon dioxide; Nanocomposite; Thin film; Sputtering; CuO; Spinel ferrite

Reversible wettability of nanostructured ZnO thin films by sol–gel method by Jianguo Lü; Kai Huang; Xuemei Chen; Jianbo Zhu; Fanming Meng; Xueping Song; Zhaoqi Sun (pp. 4720-4723).

Nanostructured ZnO thin films were deposited on Si(111) and quartz substrate by sol–gel method. The thin films were annealed at 673K, 873K, and 1073K for 60min. Microstructure, surface topography, and water contact angle of the thin films have been measured by X-ray diffractometer, atomic force microscopy, and water contact angle apparatus. XRD results showed that the ZnO thin films are polycrystalline with hexagonal wurtzite structure. AFM studies revealed that rms roughness changes from 2.3nm to 7.4nm and the grain size grow up continuously with increasing annealing temperature. Wettability results indicated that hydrophobicity of the un-irradiated ZnO thin films enhances with annealing temperature increase. The hydrophobic ZnO surfaces could be reversibly switched to hydrophilic by alternation of UV illumination and dark storage (thermal treatment). By studying the magnitude and the contact angle reduction rate of the light-induced process, the contribution of surface roughness is discussed.

Keywords: ZnO; Sol–gel; Surface topography; Reversible wettability; Hydrophobicity

Low-temperature growth of ZnO nanorods on PET fabrics with two-step hydrothermal method by Zhaoyi Zhou; Yaping Zhao; Zaisheng Cai (pp. 4724-4728).

An effective low-temperature growth method to fabricate hexagonally oriented ZnO nanorod arrays onto PET fabrics is reported. The effect of substrate pre-treatment and C₆H₁₂N₄ concentration on the structure of ZnO nanorod arrays were investigated in details by X-ray diffraction (XRD), FE-SEM and ultraviolet protection factor (UPF). The results show that substrate pre-treatment, C₆H₁₂N₄ concentration indeed have great influence on the growth of ZnO nanorod arrays. It is indispensable to introduce a ZnO seed layer on the substrate and under growth condition of n(C₆H₁₂N₄): n[Zn(NO₃)₂]=1:1, T=90°C, t=3h, the well-aligned ZnO nanorod arrays with 40–50nm in diameter and 300–400nm in length were achieved on the pre-treated PET fabrics. The ZnO nanorods grown on PET fabrics possessed an ultrahigh ultraviolet protection factor of 480.52 in this study, indicating an excellent protection against ultraviolet radiation in comparison with the untreated PET fabrics.

Keywords: ZnO nanorods; Hydrothermal; ZnO seed; UV-blocking

Molecular modeling study on inhibition performance of imidazolines for mild steel in CO₂ corrosion by Jinxiang Liu; Weizhao Yu; Jun Zhang; Songqing Hu; Long You; Guimin Qiao (pp. 4729-4733).

Corrosion inhibiting performance of 1-hydroxyethyl-2-heptadecylimidazoline (A) and 1-aminoethyl-2-heptadecylimidazoline (B) for mild steel was evaluated by combination of quantum chemistry calculation, molecular mechanics, and molecular dynamics simulation. The calculated results by quantum chemistry method demonstrated that frontier orbitals of A and B molecules are mainly located on imidazoline rings, and molecule B possesses higher reactivity than molecule A. The calculated results by molecular mechanics and molecular dynamics simulation presented that these two inhibitor molecules could form dense and high-coverage membranes to prevent diffusion of reactive corrosive species to metal surface. Furthermore, the adsorption energy, cohesive energy, and adsorption angle demonstrated that the binding affinity and stability of B membrane was remarkably greater than that of A, which indicated that B had better inhibition performance in CO₂ corrosion. The calculated results were well accorded with previous reported experimental results. These researches implied that molecular modeling might be an effective approach to assess inhibition performance, which has potential application in design of new inhibitors.

Keywords: Imidazoline; Corrosion inhibitor; Molecular modeling

Thermal stability of CdZnO thin films grown by molecular-beam epitaxy by L. Li; Z. Yang; Z. Zuo; J.H. Lim; J.L. Liu (pp. 4734-4737).

CdZnO thin films with near-band-edge (NBE) photoluminescence (PL) emission from 2.39eV to 2.74eV were grown by plasma-assisted molecular-beam epitaxy on c-plane sapphire substrates with 800°C in situ annealing. CdZnO thin films evolve from pure wurtzite (wz) structure, to mixture of wz and rock-salt (rs) structures confirmed by X-ray diffraction studies. Rapid-thermo-annealing (RTA) was performed on in situ annealed CdZnO samples. Pure wz CdZnO shows insignificant NBE PL peak shift after RTA, while mixture structure CdZnO shows evident blue shifts due to phase change after annealing, indicating the rs phase CdZnO changes to wz phase CdZnO during RTA process.

Keywords: PACS; 78.55.Et; 68.60.Dv; 81.15.Hi; 81.40.Ef; 81.40.TvZnO; Thermal stability; Molecular-beam epitaxy; II–VI semiconductors; X-ray diffraction; Photoluminescence

Manipulation and behavior modeling of one-dimensional nanomaterials on a structured surface by Sen Wu; Xing Fu; Xiaodong Hu; Xiaotang Hu (pp. 4738-4744).

Different diameters of multiwall carbon nanotubes (CNTs) are manipulated by a cantilever tip of an atomic force microscope (AFM) to investigate the motion properties of one-dimensional nanomaterials on a structured surface. To describe the mechanical behaviors of this kind of samples, two mechanical models based on continuum mechanics are proposed. Through foreseeable manipulation procedures, we are able to position the tubes onto pre-etched micro trenches, and then measure their Young's moduli by the three-point bending method. Both string-like and beam-like deformation forms are observed on the tested samples. Additionally, we present a reparable ‘collapse’ phenomenon of the nanotube bridges.

Keywords: AFM; Behavior modeling; Nanomanipulation; One-dimensional; Structured surface

Surface treatments toward obtaining clean GaN(0001) from commercial hydride vapor phase epitaxy and metal-organic chemical vapor deposition substrates in ultrahigh vacuum by Azusa N. Hattori; Katsuyoshi Endo; Ken Hattori; Hiroshi Daimon (pp. 4745-4756).

We studied processes of cleaning GaN(0001) surfaces on four different types of wafers: two types were hydride vapor phase epitaxy (HVPE) free-standing substrates and two types were metal-organic chemical vapor deposition (MOCVD) films grown on these HVPE substrates and prepared by annealing and/or Ar ion sputtering in ultra high vacuum. We observed the surfaces through treatments using in situ low-energy electron diffraction (LEED), reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), and Auger electron spectroscopy, and also using ex situ temperature programmed desorption, X-ray photoelectron spectroscopy, X-ray diffraction, and secondary ion mass spectrometry. For HVPE samples, we obtained relatively clean surfaces under optimized three-step annealing conditions (200°C for 12h+400°C for 1h+500°C for 5min) without sputtering, after which the surface contamination of oxide and carbide was reduced to∼20% of that before annealing. Clear GaN(0001)1×1 patterns were obtained by LEED and RHEED. STM images showed flat terraces of∼10nm size and steps of∼0.5nm height. Upon annealing the HVPE-GaN samples at a much higher temperature (>550°C), three-dimensional (3D) islands with facets were formed and the surface stoichiometry was broken down with the desorption of nitrogen in the form of ammonia, since the samples include hydrogen as an impurity. Ar⁺ sputtering was effective for removing surface contamination, however, postannealing could not recover the surface roughness but promoted the formation of 3D islands on the surface. For MOCVD/HVPE homoepitaxial samples, the surfaces are terminated by hydrogen and the as-introduced samples showed a clear1×1 structure. Upon annealing at 500–600°C, the surface hydrogen was removed and a3×3 reconstruction structure partially appeared, although a1×1 structure was dominant. We summarize the structure differences among the samples under the same treatment and clarify the effect of crystal quality, such as dislocations, the concentration of hydrogen impurities, and the residual reactant molecules in GaN films, on the surface structure.

Keywords: PACS; 68.37.Ef; 68.47.Fg; 68.43.Vx; 68.55.agGaN; Scanning tunneling microscopy; Low-energy electron diffraction; Reflection high-energy electron diffraction; Surface structure; Surface preparation

Influence of dopant level on structural, optical and magnetic properties of Co-doped anatase TiO₂ nanoparticles by K. Karthik; S. Kesava Pandian; K. Suresh Kumar; N. Victor Jaya (pp. 4757-4760).

Cobalt-doped TiO₂ nanoparticles were synthesized by sol–gel method. The associated structural, optical, compositional and magnetic properties of the nanoparticles as a function of cobalt concentration have been systematically studied. The X-ray powder diffraction reveals that all samples have pure anatase phase tetragonal system and the lattice parameter analysis indicated that Co ions may substitute into the lattice of TiO₂. The average particle size is 15nm, when found through transmission electron microscope. Optical spectroscopy measurement showed that the bandgap value decreases upon increasing Co concentration. The magnetic measurements revealed that the enhanced room temperature ferromagnetism (RTFM) strongly depends on the doping content.

Keywords: Nanoparticles; Sol–gel method; Anatase TiO; ₂; Magnetic measurements

Erratum to “The effect of lanthanide impurities on the physical properties of half-metallic ferromagnet Co₂MnSi” [Appl. Surf. Sci. 255 (2008) 685–687] by R. Tetean; L. Chioncel; E. Burzo; N. Bucur; A. Bezergheanu; I.G. Deac (pp. 4761-4761).

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Applied Surface Science (v.256, #14)

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Applied Surface Science (v.256, #14)