Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Applied Surface Science (v.252, #21)
The electron counting rule and passivation of compound semiconductor surfaces by G.P. Srivastava (pp. 7600-7607).
A brief review is presented of the role of electron counting rule (ECR) in explaining structural stability and passivation of compound semiconductor surfaces. While III–V(1 1 0) and majority of III–V(0 0 1) and III–V(1 1 1) surfaces reconstruct in accordance with the ECR, there are a few low- and high-index surfaces which disobey the ECR but stabilize by sustaining significant elastic deformation in the surface region. We explain the latter scenario with the help of computational results for the geometric and electronic structure of GaSb(0 0 1)-(1×3), GaSb(0 0 1)-c(2×6), InP(1 1 1)A-(3×3), and GaAs(1 1 1)B–Sb(1×3). We also discuss hydrogen passivation of these surfaces. It is pointed out that the recently observed stable InP(1 1 1)A-(3×3) surface can be both chemically and electronically passivated by exposing it to a hydrogen gas of one quarter of a monolayer coverage.
Keywords: PACS; 68.35; 71.15; 73.20Compound semiconductor surfaces; Surface reconstructions; Surface passivation; Density functional theory; Pseudopotential method
Computing surface dipoles and potentials of self-assembled monolayers from first principles by Amir Natan; Leeor Kronik; Yoram Shapira (pp. 7608-7613).
We discuss methodological aspects of first principles calculations of surface dipoles and potentials in general, and surface-adsorbed self-assembled monolayers in particular, using density functional theory with a slab/super-cell approach. We show that calculations involving asymmetric slabs may yield highly erroneous results for the surface dipole and demonstrated the efficacy of a simple dipole correction scheme. We explain the importance of the electrostatic dipole distribution, show how to compute it, and establish conditions for the equivalence of calculations for the dipole distribution and the electrostatic potential distribution.
Keywords: Density functional theory; Dipole layer; Work function; Self-assembled monolayers
Surface structure investigations using noncontact atomic force microscopy by J.J. Kolodziej; B. Such; M. Goryl; F. Krok; P. Piatkowski; M. Szymonski (pp. 7614-7623).
Surfaces of several AIIIBV compound semiconductors (InSb, GaAs, InP, InAs) of the (001) orientation have been studied with noncontact atomic force microscopy (NC-AFM). Obtained atomically resolved patterns have been compared with structural models available in the literature. It is shown that NC-AFM is an efficient tool for imaging complex surface structures in real space. It is also demonstrated that the recent structural models of III–V compound surfaces provide a sound base for interpretation of majority of features present in recorded patterns. However, there are also many new findings revealed by the NC-AFM method that is still new experimental technique in the context of surface structure determination.
Keywords: PACS; 68.35.Bs; 68.37.Ps; 68.47.FgSurface structure; III–V semiconductors; Atomic force microscopy
Rare-earth gate oxides for GaAs MOSFET application by Kwang-Ho Kwon; Jun-Kyu Yang; Hyung-Ho Park; Jongdae Kim; Tae Moon Roh (pp. 7624-7630).
Rare-earth oxide films for gate dielectric on n-GaAs have been investigated. The oxide films were e-beam evaporated on S-passivated GaAs, considering interfacial chemical bonding state and energy band structure. Rare-earth oxides such as Gd2O3, (Gd xLa1− x)2O3, and Gd-silicate were employed due to high resistivity and no chemical reaction with GaAs. Structural and bonding properties were characterized by X-ray photoemission, absorption, and diffraction. The electrical characteristics of metal-oxide-semiconductor (MOS) diodes were correlated with material properties and energy band structures to guarantee the feasibility for MOS field effect transistor (FET) application.Gd2O3 films were grown epitaxially on S-passivated GaAs (001) at 400°C. The passivation induced a lowering of crystallization temperature with an epitaxial relationship of Gd2O3 (440) and GaAs (001). A better lattice matching relation between Gd2O3 and GaAs substrate was accomplished by the substitution of Gd with La, which has larger ionic radius. The in-plane relationship of (Gd xLa1− x)2O3 (440) with GaAs (001) was found and the epitaxial films showed an improved crystalline quality. Amorphous Gd-silicate film was synthesized by the incorporation of SiO2 into Gd2O3. These amorphous Gd-silicate films excluded defect traps or current flow path due to grain boundaries and showed a relatively larger energy band gap dependent on the contents of SiO2. Energy band parameters such as Δ EC, Δ EV, and Eg were effectively controlled by the film composition.
Keywords: GaAs; MOS; Gd; 2; O; 3; (Gd; x; La; 1−; x; ); 2; O; 3; Gd-silicate; S-passivation; Epitaxial growth; Amorphous; Band gap; Band offsetPACS; 81.05.Ea; 85.30.Tv; 81.65.Rv; 61.43.Dq
Charge transient spectroscopy measurements of GaAs metal–insulator–semiconductor structures by S. Kochowski; M. Szydłowski; I. Thurzo; D.R.T. Zahn (pp. 7631-7635).
The Au/Pd/Ti–SiO2–(n)GaAs structures with and without (NH4)2S x treated gallium arsenide surface, previously analysed by impedance spectroscopy (IS) method, have been investigated using charge transient spectroscopy (QTS) technique. The isothermal QTS spectra of MIS structures kept at room temperature under set of quiescent biases have been recorded in response to both negative and positive pulses of fixed small amplitudes. Two types of charge relaxation characterized by time constant values have been evidenced. The attempt to compare QTS results with ones obtained by impedance spectroscopy method has been presented.
Keywords: PACS; 73.20.At; 73.40.QvGallium arsenide; Metal–insulator–semiconductor structure; Charge transient spectroscopy; Electrical properties and measurements
Probing electrical properties of molecule-controlled or plasma-nitrided GaAs surfaces: Two different tools for modifying the electrical characteristics of metal/GaAs diodes by M. Ambrico; M. Losurdo; P. Capezzuto; G. Bruno; T. Ligonzo; H. Haick (pp. 7636-7641).
This work shows how partial monolayer of organic molecules or radio-frequency remote plasma surface treatment affects the electrical transport across Au/ n-GaAs junctions. In the first case, a series of molecules with systematically varying dipole moment were adsorbed on n-GaAs surfaces, whereas in the second case GaN ultra-thin layers with different thickness were formed by N2–H2 GaAs plasma nitridation, prior to contact deposition. The characteristics of electrical charge transport across the resulting interfaces were studied by current–voltage ( I– V), internal photoemission (IPE), and capacitance–voltage ( C– V) techniques. In this way, we find that the simplest description for the experimentally observed data is in terms of two different barrier heights, rather than one barrier height, at the interface. The first could be identified with areas free of modified GaAs, and the second with areas controlled by electrostatic effects of adjacent dipolar domains, which affects also semiconductor regions under the film's pinholes.
Keywords: PACS; 81.07.Pr; 81.15.Gh; 85.30.Kk; 85.65.+hGaAs; GaN; Plasma; Monolayer; Interface; Diode; Barrier height
Micro-Raman spectroscopy of disordered and ordered sulfur phases on a passivated GaAs surface by T. BÅ‚achowicz; G. Salvan; D.R.T. Zahn; J. Szuber (pp. 7642-7646).
The depletion layer width and band bending of passivated n-type Sn doped GaAs(100) between subsequent steps of chemical treatment as well as after a single run treatment were investigated by micro-Raman light scattering by longitudinal optical phonons and coupled phonon–plasmon modes. Experiments were carried out ex situ at room temperature. We conclude that all observed lineshape changes are due to band bending and to an amorphous surface phase represented by a broad spectral component. We applied two passivation methods. One was based on (NH4)2S x solution and lasted 30min. The second was based on the S2Cl2 solution and lasted 10s. These enabled identification of surface regions of different amorphousness and for faster passivation places of enlarged and completely reduced band bending.
Keywords: PACS; 78.30.−j; 81.65.−b; 63.22.+m; 71.55.JvGallium arsenide; Sulfur passivation; Raman spectroscopy; Surface morphology; (NH; 4; ); 2; S; x; S; 2; Cl; 2
Comparative study of the GaAs(100) surface cleaned by atomic hydrogen by P. Tomkiewicz; A. Winkler; J. Szuber (pp. 7647-7658).
In attempt to correlate electronic properties and chemical composition of atomic hydrogen cleaned GaAs(100) surface, high-resolution photoemission yield spectroscopy (PYS) combined with Auger electron spectroscopy (AES) and mass spectrometry has been used. Our room temperature investigation clearly shows that the variations of surface composition and the electronic properties of a space charge layer as a function of atomic hydrogen dose display three successive interaction stages. There exists a contamination etching stage which is observed up to around 250L of atomic hydrogen dose followed by a transition stage and a degradation stage which is observed beyond 700L of exposure. In the first stage, a linear shift in the surface Fermi level is observed towards the conduction band by 0.14eV, in agreement to the observed restoration of the surface stoichiometry and contamination removal. The next stage is characterized by a drop in ionization energy and work function, which quantitatively agrees with the observed Ga-enrichment as well as the tail of the electronic states attributed to the breaking As-dimers. As a result of the strong hydrogenation, the interface Fermi level EF− Ev has been pinned at the value of 0.75eV what corresponds to the degradation stage of the GaAs(100) surface that exhibits metallic density of states associated with GaAs antisites defects. The results are discussed quantitatively in terms of the surface molecule approach and compared to those obtained by other groups.
Keywords: PACS; 81.05.Ea; 79.60.−i; 73.20.−r; 73.20.AtGaAs; Atomic hydrogen cleaning; Photoemission spectroscopy; Auger electron spectroscopy; Mass spectrometry; Surface states; Fermi level pinning; Work function; Ionization energy
XPS analysis of surface chemistry of near surface region of epiready GaAs(100) surface treated with (NH4)2S x solution by S. Arabasz; E. Bergignat; G. Hollinger; J. Szuber (pp. 7659-7663).
In this work we analyze the effect of (NH)2S x wet treatment on the GaAs(100) covered with “epiready� oxide layer without any pretreatment in order to check the removal of oxides and carbon-related contamination, and the formation of sulfur species. The sulfidation procedure consisted of epiready sample dipping (at room and 40°C temperatures) in an ammonium polysulfide solution combined with a UHV flash annealing up to 500°C.The inspection of the XPS As 2p3/2 and Ga 2p3/2 spectra taken at surface sensitive mode revealed: (i) the temperature-dependent reduction of the amount of GaAs oxides and carbon contamination after sulfidation, and almost their complete removal after subsequent annealing, (ii) the creation of sulfur bonds with both Ga and As, with more thermally stable Ga–S bonds, and (iii) the slight reduction in elemental arsenic amount.
Keywords: PACS; 73.61.Ey; 81.65.RvGaAs; Passivation; Sulfidation; XPS
Passivation of InP-based HBTs by Z. Jin; K. Uchida; S. Nozaki; W. Prost; F.-J. Tegude (pp. 7664-7670).
The surface effects, the (NH4)2S and low-temperature-deposited SiN x passivations of InP-based heterostructure bipolar transistors (HBTs) have been investigated. The surface recombination current of InP-based HBTs is related to the base structures. The (NH4)2S treatment for InGaAs and InP removes the natural oxide layer and results in sulfur-bonded surfaces. This can create surface-recombination-free InP-based HBTs. Degradation is found when the HBTs were exposed to air for 10 days. The low-temperature-deposited SiN x passivation of InGaAs/InP HBTs causes a drastic decrease in the base current and a significant increase in the current gain. The improvement in the HBT performance is attributed to the low deposition temperature and the effect of N2 plasma treatment in the initial deposition process. The SiN x passivation is found to be stable. S/SiN x passivation of InGaAs/InP HBTs results in a decrease in the base current and an increase in the current gain. The annealing process can cause the base current to decrease further and the current gain increase.
Keywords: PACS; 73.20.At; 73.40.Kp; 73.50.Gr; 73.61.Ey; 81.65.Rv; 85.30.PqInP; Heterostructure bipolar transistor; Passivation; Sulfur; Silicon nitride
GaN nucleation on (0001)-sapphire via ion-induced nitridation of gallium by A. Sidorenko; H. Peisert; H. Neumann; T. Chassé (pp. 7671-7677).
The growth of epitaxial GaN films on (0001)-sapphire has been investigated using X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED). In order to investigate the mechanism of the growth in detail, we have focused on the nitridation of pre-deposited Ga layers (droplets) using ion beam-assisted molecular beam epitaxy (IBA-MBE). Comparative analysis of XPS core-level spectra and LEED patterns reveals, that nitride films nucleate as epitaxial GaN islands. The wetting of the surface by GaN proceeds via reactive spreading of metallic Ga, supplied from the droplets. The discussed growth model confirms, that excess of metallic Ga is beneficial for GaN nucleation.
Keywords: PACS; 81.05.Ea; 82.80.Pv; 61.14.HgGaN nucleation; X-ray photoelectron spectroscopy (XPS); Low energy electron diffraction (LEED); Epitaxial growth
Atomic geometry, electronic states and possible hydrogen passivation of the InP(1 1 1)A surface by K. Chuasiripattana; G.P. Srivastava (pp. 7678-7683).
We present a first-principles theoretical study of the atomic geometry and electronics states of the InP(1 1 1)A surface under In- and P-rich conditions. The In-rich surface, characterised by an In vacancy per unit (2×2) cell, obeys the electron counting rule (ECR) and is semiconducting. Under P-rich conditions we have considered two surface reconstructions: (2×2) with 3/4 monolayer (ML) P coverage and (3×3) with 1 ML coverage. In complete agreement with a recent experimental work by Li et al., it is found that the (3×3) reconstruction is more stable than the (2×2) reconstruction. However, the (3×3) reconstruction has a metallic band structure and thus does not satisfy the ECR. The stability of this reconstruction is explained to arise from a competition between the ECR and a significant elastic deformation in the surface region. We confirm the suggestion by Li et al. that this surface can be passivated both chemically as well as electronically with 1/4 ML coverage of hydrogen.
Keywords: Density functional calculations; Surface electronic phenomena; Electron counting rule; Surface passivation; InP(1 1 1)
Structure and composition of chemically prepared and vacuum annealed InSb(001) surfaces by O.E. Tereshchenko (pp. 7684-7690).
The InSb(001) surfaces chemically treated in HCl–isopropanol solution and annealed in vacuum were studied by means of X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and electron energy-loss spectroscopy (EELS). The HCl–isopropanol treatment removes indium and antimony oxides and leaves on the surface about 3ML of physisorbed overlayer, containing indium chlorides and small amounts of antimony, which can be thermally desorbed at 230°C. The residual carbon contaminations were around 0.2–0.4ML and consisted of the hydrocarbon molecules. These hydrocarbon contaminations were removed from the surface together with the indium chlorides and antimony overlayer. With increased annealing temperature, a sequence of reconstructions were identified by LEED: (1×1), (1×3), (4×3), and (4×1)/c(8×2), in the order of decreasing Sb/In ratio. The structural properties of chemically prepared InSb(001) surface were found to be similar to those obtained by decapping of Sb-capped epitaxial layers.
Keywords: PACS; 73.61.Ey; 81.65.Rv; 81.65; 81.65.C; 68.35.BsInSb; HCl–isopropanol treatment; Passivation; Low energy electron diffraction; X-ray photoelectron spectroscopy; Electron energy-loss spectroscopy
Silicon surface passivation by static charge by János Mizsei (pp. 7691-7699).
A properly passivated silicon surface is chemically stable, and all interface properties are constant. The silicon dioxide layers fulfil the chemical stability requirements; however, their surface and interface charges have effect on the silicon surface potential barrier. Positive charge is usually assumed at the oxide–silicon interface, thus depletion or inversion layer develops in the case of p and accumulation in the case of n-type silicon.The surface of silicon dioxide can be charged macroscopically by corona charger or by conductive rubber stamp, microscopically by a tip of some scanning probe microscope (STM or AFM). The oxide surface usually retains the charges for a long time, however in the case of ultra-thin or other leaky oxide continuous charging it is necessary to keep the constant surface potential.The main purpose of this work is to summarize the possibilities of charging up the surface, the effect of the surface and interface charge on the surface properties of the silicon. The rearrangement of the surface charges will also be discussed.
Keywords: PACS; 81.65.Rv; 73.30+y; 73.25.+iPassivation; Surface voltage; Vibrating capacitor; SPV; Charge PCD; Native oxide; Silicon surface; Tunnel current; Surface charge
Method of observation of low density interface states by means of X-ray photoelectron spectroscopy under bias and passivation by cyanide ions by H. Kobayashi; T. Sakurai; Y. Yamashita; T. Kubota; O. Maida; M. Takahashi (pp. 7700-7712).
X-ray photoelectron spectroscopy (XPS) measurements under bias can observe low density interface states for metal-oxide-semiconductor (MOS) diodes with low densities. This method can give energy distribution of interface states for ultrathin insulating layers for which electrical measurements cannot be performed due to a high density leakage current. During the XPS measurements, a bias voltage is applied to the rear semiconductor surface with respect to the ∼3nm-thick front platinum layer connected to the ground, and the bias voltage changes the occupation of interface states. Charges accumulated in the interface states shift semiconductor core levels at the interface, and thus the analysis of the bias-induced shifts of the semiconductor core levels measured as a function of the bias voltage gives energy distribution of interface states. In the case of Si-based MOS diodes, the energy distribution and density of interface states strongly depend on the atomic density of silicon dioxide (SiO2) layers and the interfacial roughness, respectively. All the observed interface state spectra possess peaked-structures, indicating that they are due to defect states. An interface state peak near the Si midgap is attributable to isolated Si dangling bonds at the interface, while those above and below the midgap to Si dangling bonds interacting weakly with Si or oxygen atoms in the SiO2 layers. A method of the elimination of interface states and defect states in Si using cyanide solutions has been developed. The cyanide method simply involves the immersion of Si in KCN solutions. Due to the high Si–CN bond energy of ∼4.5eV, the bonds are not ruptured at 800°C and upon irradiation. The cyanide treatment results in the improvement of the electrical characteristics of MOS diodes and solar cells.
Keywords: PACS; 71.55.Cn; 73.40.Qv; 82.80.Pv; 81.60.CpInterface states; XPS bias; Si; Ultrathin silicon oxide; Defect passivation; Cyanide ion
Passivation of Si and a-Si:H surfaces by thin oxide and oxy-nitride layers by E. PinÄ?Ãk; H. Kobayashi; J. Rusnák; M. Takahashi; R. Brunner; M. Jergel; A. Morales-Acevedo; L. Ortega; J. KákoÅ¡ (pp. 7713-7721).
An aim of the contribution is focused predominantly on investigation of electrical interface properties of MIS structures consisting of silicon-based substrates, which were passivated by 1.5–12nm silicon dioxide, silicon nitride and/or silicon oxy-nitride layers. Substrates of different structural properties were used—crystalline Si (c-Si), amorphous hydrogenated silicon (a-Si:H), and silicon layer deposited by plasma enhanced chemical vapor deposition (PECVD). A stress was laid upon structures prepared on n moderately doped c-Si. The paper presents also changes of structural properties of a-Si:H surface after Ar low energy beam impact. For the first time we are presenting important results concerning utilization of X-ray diffraction with β filter in investigation of a-Si:H cluster structure. Considerable part of the contribution is devoted to investigation of electrical properties of Al/Si3N4/Si (2–3nm)/GaAs structures with aim to clarify the particular effect of the ultrathin Si interlayer in the structure. Our observations indicate that the silicon interlayer can act as delta doping of GaAs and/or as quantum well. Therefore, the experimental results are compared and discussed with calculated ones obtained by application of our theoretical description of electron emission of quantum well.
Keywords: PACS; 81.65; 82.30; 78.66; 81.60.CpCrystalline silicon; Amorphous hydrogenated silicon; Silicon dioxide; Quantum well; Interface; Cyanide treatment
On a presence of Si mH n clusters in a-Si:H/c-Si structures by M. Kopáni; E. PinÄ?Ãk; H. Kobayashi; M. Takahashi; N. Fujiwara; R. Brunner; M. Jergel; L. Ortega (pp. 7722-7725).
Dominant aim of the paper was to verify the existence of the Si mH n clusters in a-Si:H layers. Thin layers were deposited by plasma-enhanced chemical vapor deposition (PECVD) on both glass and crystalline silicon substrates. Their IR and structural properties were investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction at grazing incidence angle (XRDGI). We have found that the layer probably consists of larger structurally ordered parts corresponding to Si mH n clusters and separated groups of (Si-H x) N. The ordered parts could be identified as some of Si mH n clusters ranging from (10, 16) to (84, 64) represented by corresponding vibration frequencies in three following IR regions: 600–750, 830–900 and 2080–2180cm−1. XRDGI measurement indicates that diffraction maximum at around 2Θ=28° can be attributed to an existing Si mH n cluster.
Keywords: PACS; 61.72.Dd; 61.43.Dq; 78.30.jAmorphous hydrogenated silicon; X-ray diffraction; Fourier transform infrared spectroscopy; Clusters; solar cell
The intrinsic lifetime of low-frequency zone-centre phonon modes in silicon nanowires and carbon nanotubes by S.P. Hepplestone; G.P. Srivastava (pp. 7726-7729).
Estimates of the intrinsic lifetime of low-frequency zone-centre phonon modes in silicon nanowires and carbon nanotubes have been presented from the application of Fermi’s golden rule formula based upon an elastic continuum model for cubic anharmonicity. In particular, results have been presented for the lowest non-zero mode in both nanostructures, and also the breathing mode in the nanotube. Except for the ultrathin nanowire, the lifetime increases with size and decreases with an increase in temperature. Typically, these modes have a lifetime of the order of nanoseconds, almost a thousand times larger than the lifetimes of optical phonon modes in the corresponding bulk materials. Also, at room temperature the lifetime of the lowest non-zero mode is nearly an order of magnitude larger in the (20,20) nanotube than in the nanowire of similar thickness (width 2.2 nm).
Keywords: Silicon nanowires; Carbon nanotubes; Phonons; Lifetime
XPS depth profiling studies of L-CVD SnO2 thin films by M. Kwoka; L. Ottaviano; M. Passacantando; S. Santucci; J. Szuber (pp. 7730-7733).
In this paper we present the results of the XPS atomic depth profile analysis, using ion beam sputtering, of L-CVD SnO2 thin films grown on an atomically clean SiO2 substrate after annealing at 400°C in dry atmospheric air. From the evolution of the Sn 3d5/2, O 1s, Si 2p and C 1s core level peaks our experiments allowed the determination of the in depth atomic concentration of the main components of the SnO2/SiO2 interface. Thin (few nm) nearly stoichiometric SnO2 films are present at the topmost layer of the thin films, and progressive intermixing with SnO and silicon oxide is observed at deeper layer. The interface between the Sn and the Si oxide layers (i.e. the effective Sn oxide thickness) is measured at 13nm.
Keywords: PACS; 68.55.Jk; 81.70.Jb; 82.80.PvTin dioxide; Thin films; Depth profiling; XPS
Comparative photoemission study of the electronic properties of L-CVD SnO2 thin films by M. Kwoka; L. Ottaviano; M. Passacantando; G. Czempik; S. Santucci; J. Szuber (pp. 7734-7738).
In this work we present the results of comparative XPS and PYS studies of electronic properties of the space charge layer of the L-CVD SnO2 thin films after air exposure and subsequent UHV annealing at 400°C, with a special emphasis on the interface Fermi level position.From the centre of gravity of binding energy of the main XPS Sn 3d5/2 line the interface Fermi level position EF− Ev in the band gap has been determined. It was in a good correlation with the value estimated from the offset of valence band region of the XPS spectrum, as well as from the photoemission yield spectroscopy (PYS) measurements. Moreover, from the valence band region of the XPS spectrum and PYS spectrum two different types of filled electronic band gap states of the L-CVD SnO2 thin films have been derived, located at 6 and 3eV with respect to the Fermi level.
Keywords: PACS; 79.60.−I; 73.20.−r; 73.20.AtTin dioxide; Thin films; L-CVD deposition; Electronic properties of space charge layer; Fermi level position; Electronic band gap states
Formation of photoresist-free patterned ZnO film containing nano-sized Ag by photochemical solution deposition by Chae-Seon Hong; Hyeong-Ho Park; Seok-Joo Wang; Jooho Moon; Hyung-Ho Park; Ross H. Hill (pp. 7739-7742).
Direct patterning of ZnO thin film was realized without photoresist and dry etching by photochemical solution deposition. Photosensitive ortho-nitrobenzaldehyde was introduced into the solution precursors as a stabilizer and contributed to form a cross-linked network structure during photochemical reaction. Ag nanoparticles were prepared with uniform size distribution using trisodium citrate as a capping agent to incorporate into ZnO thin film in order to reduce the electrical resistance of the film. The optical and electrical properties of ZnO film with or without Ag nanoparticles after anneal at various temperatures were investigated. The reduction in transmittance with the increase in anneal temperature was observed and also the increase in the electrical resistance was found. The increase in the surface roughness of ZnO film and the decrease of surface oxygen deficiencies were mainly responsible for the decrease in transmittance and the increase in electrical resistance, respectively.
Keywords: PACS; 73.61.GaZnO thin film; Nano-sized Ag particles; Direct-patterning; Sol–gel process
Differences between surface and bulk refractive indices of a-In xSe1− x by A. Michalewicz; M. Nowak; M. Kępińska (pp. 7743-7747).
Thin films of amorphous indium selenide compounds (a-In xSe1− x) are important, e.g. for photovoltaics. The feature of merit in such applications is also the real part of refractive index n of this material. The data on n in literature are divergent. In this paper, the results of investigations on n in the bulk as well as in the interface layers of thin films of a-In xSe1− x are presented. The measurements had been performed using optical transmittance and reflectance in spectral range from 1.24 to 1.96eV of linear polarized radiation that hit the samples with angles of incidence from 0° to 80°. Investigations had been done for sample temperatures from 80 to 340K. It was found that the refractive index for areas at the free surface nf is bigger than the refractive index nb at the interface of thin film–substrate. The averaged over thin film thickness value of real part refractive indexn¯ have the biggest value in all spectral range. Values of these coefficients increase with increasing the temperature.
Keywords: PACS; 78.20.Ci; 78.40.Fy; 78.66.Jg; 81.05.GcIndium–selenide; Amorphous thin films; Optical properties