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Applied Surface Science (v.241, #1-2)

Author Index (pp. i-iv).

Subject Index (pp. v-xix).

Characterization of artificial nanostructures and nanomaterials by Daisuke Fujita; Giyuu Kido; Masahiro Tosa; Michiko Yoshitake; Yasushi Yamauchi (pp. 1-1).

Mechanical distinction and manipulation of atoms based on noncontact atomic force microscopy by Seizo Morita; Insook Yi; Yoshiaki Sugimoto; Noriaki Oyabu; Ryuji Nishi; �scar Custance; Masayuki Abe (pp. 2-8).

Using noncontact atomic force microscopy (NC-AFM), we have succeeded in imaging two-dimensional (2D) Ge islands as well as Ge atom clusters on Si(111)-(7�7) surface with atomic resolution. We have investigated the tip-sample distance dependence of NC-AFM images of oxygen adsorbed Si(111)-(7�7) surface, and achieved the chemical distinction between oxygen and Si atom species. Besides, using a soft nanoindentation based on the NC-AFM method for mechanically manipulating Si adatoms of the Si(111)-(7�7) surface, we have achieved atom removal, i.e., vertical manipulation, at tip and sample temperature of 78K as well as at room temperature (RT). In addition, as an application of this soft nanoindentation method, we have produced the lateral displacement of Si adatoms towards metastable positions in the half unit cell of the Si(111)-(7�7) reconstruction at 78K.

Keywords: PACS; 68.37.Ps; 68.35.Bs; 39.25+k; 39.30.+w; 62.25.+gNoncontact atomic force microscopy (NC-AFM); Atomic resolution; Atom distinction; Atom manipulation; Mechanical atom manipulation; Nanoindentation

Cross-sectional scanning tunneling microscopy observation of atomic arrangement in triple period-A type ordered AlInAs alloy by Shunsuke Ohkouchi; Takahisa Furuhashi; Akiko Gomyo; Kikuo Makita; Tohru Suzuki (pp. 9-13).

Atomic arrangements in a triple-period (TP)-A type ordered AlInAs layer were investigated by a cross-sectional scanning tunneling microscope (XSTM) for the first time. The distributions of cation atoms in the ordered layer were distinguished using the tunneling spectroscopy method. The XSTM image on the cleaved surface of the ordered AlInAs layer revealed the presence of ragged short-range ordering domains comprising periodic structures aligned along the [112¯] direction on the whole surface, separated by three-fold periodicity along the [111] direction. This three-fold periodic structure comprises units of In–In–Al and/or In–Al–Al. That is, the TP-A type ordered AlInAs layer comprises two kinds of three-fold periodic planes; one is composed of two InAs-like planes and one AlAs-like plane, and the other is composed of one InAs-like plane and two AlAs-like planes. In addition, a local two-fold ordered structure having alternating InAs-like and AlAs-like planes can be observed in the STM image.

Keywords: PACS; 68.35.Bs; 68.37.Ef; 73.61.EyScanning tunneling microscopy; Ordering; AlInAs; Surface reconstruction

Conductance of Pd single-atom contacts by T. Minowa; A. Fujii; M. Takeda; S. Kurokawa; A. Sakai (pp. 14-17).

We have measured the conductance of Pd single-atom contacts (SACs) at room temperature in UHV using a contact-breaking method. Transient conductance traces displayed some marginal plateaus at unspecified positions, resulting featureless conductance histograms for applied biases 0.2–0.6V. Our experimental results are consistent with our previous experiments on Pd contact relays but apparently not with the previous observations of 1 G₀ and 0.5 G₀ peaks in the conductance histogram of Pd. We consider that the structure sensitivity of the conductance of Pd SACs partly dissolves this discrepancy.

Keywords: PACS; 73.63Rt; 81.07.Lk; 73.40Jn; 66.30.QaSingle-atom contacts; Conductance; Palladium

Nanometer-scale mapping of local work function with a photon-assisted STM technique by Yasuo Nakayama; Hiroshi Kondoh; Toshiaki Ohta (pp. 18-22).

Local work-function mapping has been performed using scanning tunneling microscopy (STM) combined with visible laser light. Spatial distribution of the work function was visualized for inhomogeneous alkali-metal overlayers on a patterned Cu surface in a nanometer scale formed by nitrogen ion implantation. The spatial resolution of this technique is estimated to be in a sub-nanometer range.

Keywords: PACS; 68.37.Ef; 73.30.+yScanning tunneling microscopy; Photo-assisted STM; Work function; N implantation; Cu(1; 0; 0); Alkali metals

Non-contact atomic force microscopy study of the Sn/Si(111) mosaic phase by Y. Sugimoto; M. Abe; K. Yoshimoto; O. Custance; I. Yi; S. Morita (pp. 23-27).

We have analyzed the height dependence of the Si and Sn atoms on the 1/6 monolayer (ML) Sn/Si(111)-(√3×√3) R30° surface, also known as Sn/Si(111) mosaic phase, by means of non-contact atomic force microscopy (NC-AFM) technique. By preparing samples in which the Sn/Si(111) mosaic phase and the Si(111)-(7×7) surfaces coexist, and taking account of the proportion of bright and dim contrast atoms when comparing NC-AFM images of both surfaces, we have been able to discriminate between the two atom species forming the mosaic phase. Additionally, we have found a pronounced variation of the height of the Si adatoms with the number of first neighboring Sn adatoms in the Sn/Si(111) mosaic phase.

Keywords: PACS; 68.37.Ps; 68.35.Bs; 39.25+k; 39.30.+w; 62.25.+gNon-contact atomic force microscopy; NC-AFM; Atomic resolution; Atom identification; Si; Sn; Charge transfer

STM-induced light emission from the surface of H₂TBP porphyrin/PFP porphyrin/Cu(100) by X.-L. Guo; Z.-C. Dong; A.S. Trifonov; K. Miki; K. Kimura; S. Mashiko (pp. 28-32).

Molecular fluorescence from the surface of H₂TBP porphyrin (H₂TBPP) monolayer on the top of PFP porphyrin (PFPP) multilayers on Cu(100) substrate is studied by an ultrahigh-vacuum scanning tunneling microscope. H₂TBPP molecular luminescence spectra are well defined and in perfect matching with conventional photoluminescence spectra excited from the corresponding bulk molecule. The electronic states of H₂TBPP monolayer are effectively decoupled from the metal surface by controlling the thickness of PFPP multilayers in a nanoscale regime. The excitation mechanism is probably attributed to the hot electron injection. These results provide a new way for the development of nanoscale molecular light source and spectroscopy.

Keywords: PACS; 34.80.Gs; 68.37.Ef; 73.20.−rMolecular fluorescence; Ultrahigh-vacuum scanning tunneling microscope (UHV-STM); H; ₂; TBPP molecules; PFPP molecules; Cu(1; 0; 0) substrates

Growth and characterization of isolated nanoclusters on mixed self-assembled monolayers by Yukihiro Sakotsubo; Taizo Ohgi; Daisuke Fujita; Youiti Ootuka (pp. 33-37).

Using scanning tunneling microscope, we have investigated the formation of Au nanoclusters on self-assembled monolayers of octanethiol (CH₃(CH₂)₇SH) molecules modified with octanedithiol (HS(CH₂)₈SH). By changing the modification condition and the amount of Au deposition, it is found that the density and the size of the clusters can be controlled. The cluster-formation mechanism is discussed.

Keywords: PACS; 73.22.−f; 73.23.Hk; 61.46.+w; 68.43.−hGold nanoclusters; Self-assembled monolayer; Octanedithiol; Au(1; 1; 1); STM

Fabrication of Ti-nanowires in sapphire single crystals by Atsutomo Nakamura; Katsuyuki Matsunaga; Takahisa Yamamoto; Yuichi Ikuhara (pp. 38-42).

We report electrical conductivity of Ti-nanowires in sapphire fabricated by utilizing lattice dislocations. We evaporated metallic Ti on a sapphire plate containing high density of uniaxial dislocations, and annealed the plate at high temperatures. As a result, it was found that Ti atoms intensely segregated along the dislocations within about 5nm in diameter, indicating the formation of Ti-nanowires inside sapphire. Furthermore, the nanowires were confirmed to have significant electrical conductivity even in sapphire insulator.

Keywords: PACS; 61.72.Ff; 73.63.Nm; 68.37.LpDislocations; Sapphire; Scanning probe microscope (SPM); Electric conductivity; Quantum wires

Scanning tunneling microscopy and spectroscopy studies of graphite edges by Y. Niimi; T. Matsui; H. Kambara; K. Tagami; M. Tsukada; Hiroshi Fukuyama (pp. 43-48).

We studied experimentally and theoretically the electronic local density of states (LDOS) near single-step edges at the surface of exfoliated graphite. In scanning tunneling microscopy measurements, we observed the(3×3)R30° and honeycomb superstructures extending over 3–4 nm both from the zigzag and armchair edges. Calculations based on a density-functional-derived non-orthogonal tight-binding model show that these superstructures can coexist if the two types of edges admix each other in real graphite step edges. Scanning tunneling spectroscopy measurements near the zigzag edge reveal a clear peak in the LDOS at an energy below the Fermi energy by 20 meV. No such a peak was observed near the armchair edge. We concluded that this peak corresponds to the “edge state�? theoretically predicted for graphene ribbons, since a similar prominent LDOS peak due to the edge state is obtained by the first principles calculations.

Keywords: PACS; 61.16.Ch; 61.72.Ff; 73.20.AtEdge state; Scanning tunneling microscopy; Scanning tunneling spectroscopy; Graphite

Metal-induced nanostructures on surfaces of layered chalcogenides by S. Hollensteiner; E. Spiecker; W. J�ger (pp. 49-55).

The development of layered dichalcogenide crystal surfaces during early stages of metal deposition has been investigated, using ultra-high vacuum electron beam evaporation of copper at ambient temperature onto (0001) VSe₂ crystal surfaces as model case. Analytical transmission electron microscopy techniques, scanning electron microscopy, and atomic force microscopy have been combined to characterize the microscopic nature of the surface structures and the self-assembled formation of surface nanostructures that form as large nanostructures (lateral dimensions>100nm) and as networks of smaller nanostructures (lateral dimensions∼several 10nm). Nearly contiguous ultrathin layers of a copper-rich crystalline surface phase are observed for deposition stages at a nominal Cu coverage of 1nm and above. The observations indicate that compressive in-plane strains are induced in the VSe₂ surface layers by the formation of a copper-rich crystalline phase by intercalation, with possible contributions of an electronic charge transfer from copper atoms to the substrate during the earliest deposition stages. Above a critical value the surface layer strains are relaxed by formation of surface folds, nanostructure networks and interface dislocations.

Keywords: PACS; 81.15.Ef; 81.16.Dn; 81.05.Bx; 68.55.Jk; 68.37.LpMetal deposition; Surfaces; Self-assembled nanostructures; Layered chalcogenides; Strain relaxation; Intercalation; Transmission electron microscopy

Selective growth and characterization of nanostructures with transmission electron microscopes by M. Shimojo; S. Bysakh; K. Mitsuishi; M. Tanaka; M. Song; K. Furuya (pp. 56-60).

A new type of electron beam-induced reactions is reported. Focused electron beams, the probe size of which is about 0.8nm, were irradiated on carbon and Si substrates with an introduction of an aluminum trichloride or a gold trichloride gas in the chamber. Nanometer-sized carbon and Si rods were formed using carbon and Si substrates, respectively, by moving the beam position at a certain speed. As no aluminum, gold or chlorine was found in the rods, it is considered that chloride gases behaved as a sort of catalysis.

Keywords: PACS; 85.40Ux; 07.78+sElectron beam-induced reaction; Catalysis; Nano-fabrication; Aluminum trichloride

Electron energy-loss spectroscopic study of the surface of ceria abrasives by Shelley R. Gilliss; James Bentley; C. Barry Carter (pp. 61-67).

Surfaces of ceria (CeO₂) particles have been studied by electron energy-loss spectroscopy in a field-emission gun scanning transmission electron microscope. All the ceria particles analyzed contained Ce³⁺ at the surface. Rare-earth impurities such as La were enriched at the surface and were observed for particles ranging from tens to hundreds of nanometers in size. Fluorine in the abrasives corresponded to a lower average cerium valence. Time series investigations indicate that fluorine substitutes on the oxygen sub-lattice and is charge-balanced by some cerium changing from Ce⁴⁺ to Ce³⁺.

Keywords: PACS; 68.35DvCMP; Ceria; EELS; Segregation; Non-stoichiometry

TEM in situ observation of fracture behavior in ceramic materials by S. Ii; C. Iwamoto; K. Matsunaga; T. Yamamoto; Y. Ikuhara (pp. 68-74).

The atomic structures of crack walls due to cleavage fracture in silicon nitride (Si₃N₄) and magnesium oxide (MgO) have been investigated by in situ straining transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM) at room temperature. In the case of Si₃N₄, the crack walls on the (11�00) plane were atomically flat, which indicates that the crack propagated along a particular crystal plane without deflection. On the other hand, the cleaved crack walls in MgO were not atomically flat but contained a number of square-shaped steps with a few {010} atomic layers in height. Thus, it can be said that the cleavage crack was deflected at the atomic level during its rapid propagation. The origin of their step structures is discussed using results from molecular dynamics (MD) simulations.

Keywords: PACS; 68.37.Lp; 81.40.NpSilicon nitride (Si; ₃; N; ₄; ); Magnesium oxide (MgO); Cleavage fracture; In situ observation; Transmission electron microscopy; High-resolution electron microscopy

HRTEM study on grain boundary atomic structures related to the sliding behavior in alumina bicrystals by K. Matsunaga; H. Nishimura; S. Hanyu; H. Muto; T. Yamamoto; Y. Ikuhara (pp. 75-79).

Al₂O₃ bicrystals containing [0001] symmetric tilt Σ7 grain boundaries with different grain boundary planes of {45¯10} and {23¯10} were fabricated by diffusion bonding, and the grain boundary structures were investigated by high-resolution transmission electron microscopy (HRTEM). From HRTEM observations combined with atomistic simulations, it was found that the grain boundaries exhibited characteristic atomic arrangements, and the Σ7/{23¯10} boundary contained large open spaces at its core. In compressive creep experiments for the bicrystals, these boundaries showed quite different creep behavior, although they have the same Σ value. The measured sliding rate of Σ7/{23¯10} was much larger than that of Σ7/{45¯10}, which may be due to the open core structure formed in Σ7/{23¯10}.

Keywords: PACS; 61.72.M; 61.16.B; 62.20.HHRTEM; Grain boundary; Alumina; Creep

Surface damage induced by focused-ion-beam milling in a Si/Si p–n junction cross-sectional specimen by Zhouguang Wang; Takeharu Kato; Tsukasa Hirayama; Naoko Kato; Katsuhiro Sasaki; Hiroyasu Saka (pp. 80-86).

Focused-ion-beam (FIB) technique has been widely used to prepare device specimen for transmission electron microscopy (TEM)-based microanalysis. One artifact induced by high-energy FIB milling is surface damage in the specimen. We systematically studied the damaged amorphous layers induced by gallium FIBs with different energies in Si/Si p–n junction cross-sectional specimens. The damaged amorphous layers in the top surface during depositing protective layers by 30 and 40keV FIBs were measured to be 48 and 65nm thick, respectively. In the sidewall, the amorphous layers were observed to be 9.4, 14.5, 20.0 and 25.3nm, respectively, for the 10, 20, 30 and 40keV FIB milling. In the n- and p-type side of the p–n junction, no difference was observed for the sidewall amorphous layers. A comparison shows the top surface and the sidewall amorphous layers can be estimated simply by formulae R_p+ n·Δ R_p and n·Δ R_t by taking n=3. Our experimental results suggest that the sidewall damage can be reduced largely by using a low-energy FIB at final milling step.

Keywords: PACS; 68.37.Lp; 61.72.Tt; 06.60.WaTEM; FIB; Sample preparation; Damage effect

HRTEM and EELS characterization of atomic and electronic structures in Cu/α-Al₂O₃ interfaces by T. Sasaki; T. Mizoguchi; K. Matsunaga; S. Tanaka; T. Yamamoto; M. Kohyama; Y. Ikuhara (pp. 87-90).

Interfacial atomic structures of Cu/Al₂O₃(0001) and Cu/Al₂O₃(112¯0) prepared by the pulsed-laser deposition technique were characterized by high-resolution transmission electron microscopy (HRTEM). It was found that (111) and (001) planes of Cu were epitaxially oriented to Al₂O₃(0001) and Al₂O₃(112¯0) planes, respectively. Chemical bonding states at the interfaces were analysed by electron energy-loss spectroscopy (EELS). In oxygen–K edge energy-loss near-edge structure (O–K ELNES) of the Cu/Al₂O₃(0001) and Cu/Al₂O₃(112¯0) interfaces, a shoulder peak appeared at the lower energy side of the main peak. This indicates that Cu–O interactions were formed across these Cu/Al₂O₃ interfaces. In fact, the simulated HRTEM images based on the O-terminated interface models agreed well with the experimental ones. It can be concluded that the O-terminated interfaces were formed in the present Cu/Al₂O₃ interfaces.

Keywords: PACS; 68.37.Lp; 79.20.Uv; 61.72.MmHigh-resolution transmission electron microscopy (HRTEM); Electron energy-loss spectroscopy (EELS); Cu/Al; ₂; O; ₃; interfaces; Atomic structure; Electronic structure

Characterization of metal nanoparticles fabricated in ordered array pores of anodic porous alumina by electron-beam-induced selective deposition by Guoqiang Xie; Minghui Song; Kazutaka Mitsuishi; Kazuo Furuya (pp. 91-95).

The ordered arrays of Au nanoparticles were fabricated by electron-beam-induced selective deposition process in an ordered pore arrays of anodic porous alumina membrane. The microstructure of the as-deposited nanoparticles was characterized using high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and microdiffraction technique. It was determined that the as-deposited nanoparticles consisted of many nanocrystallites of Au metal. The size of these nanocrystallites in the as-deposited nanoparticles was smaller than 5nm.

Keywords: PACS; 81.07.−b; 61.46.+W; 68.37.LpElectron-beam-induced deposition; Anodic porous alumina; Nanoparticle; HRTEM; Microdiffraction

Structure variation of nanometer-sized Xe particles embedded in Al crystals by M. Song; K. Mitsuishi; K. Furuya; C.W. Allen; R.C. Birtcher; S.E. Donnelly (pp. 96-101).

Nanometer-sized Xe particles embedded in Al are observed with an off-Bragg condition high resolution transmission electron microscopy. It is found that a Xe particle with size of about 1nm shows quite different structural properties from those with larger sizes. It changes structure from an f.c.c. to another one, changes orientation with the same f.c.c. structure, or changes shape and sizes. These changes are attributed to (1) a high mobility of atoms on Xe/Al interface due to irradiation of 1MeV electron beam and irradiation enhanced interfacial diffusion; (2) a smaller barrier in energy for shape change of a smaller Al void where the Xe particle is constrained; (3) a larger fraction of atoms on Xe/Al interface for a smaller Xe particle.

Keywords: PACS; 61.72.Ff; 61.72.Qq; 61.46.+w; 61.82.RxXe; Al; Nanoparticle; Nanostructure; HREM

Reduction mechanism of surface oxide films and characterization of formations on pulse electric-current sintered Al–Mg alloy powders by Guoqiang Xie; Osamu Ohashi; Minghui Song; Kazutaka Mitsuishi; Kazuo Furuya (pp. 102-106).

The microstructure of interfaces between powder particles in Al–Mg alloy specimens sintered by pulse electric-current sintering (PECS) process was characterized using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). The crystalline precipitates with nano-size in the interface were observed in all of Al–Mg alloy specimens. The composition was determined to be MgAl₂O₄ or MgO, or both of them, which depended on Mg content in alloy powder and sintering temperature. The precipitates were suggested to contribute to reduction reaction of Mg with oxide films originally covered at powder particles surface.

Keywords: PACS; 68.37.−d; 68.35.Dv; 81.30.MhReduction reaction; HRTEM; Pulse electric-current sintering; Al–Mg alloy; Oxide film

Characterization of nanometer-sized dendritic form structures fabricated on insulator substrates with an electron-beam-induced deposition in a TEM by M. Song; K. Mitsuishi; M. Takeguchi; K. Furuya (pp. 107-112).

Nanometer-sized dendrite-like structures with a designed element, W, is fabricated on an insulator substrate, Al₂O₃, with an electron-beam-induced decomposition (EBID) in a transmission electron microscope (TEM). The fabricated structures are characterized with convention and high resolution TEM. The dendritic structure with tips in about 3nm grows radially at convex surface of a substrate. The bcc structural W crystal grains in nanometers are composed in the dendrites. A mechanism is proposed to explain the growth and morphology of the deposit involving a charge-up on surface, a movement to and an accumulation of charges at convex surface or tips of substrate or the branched deposit.

Keywords: PACS; 81.01.−b; 07.78; 81.15.Gh; 81.16.−cElectron-beam-induced deposition; TEM; Nanostructure; Dendrite; Nanofabrication

Characterization of nanolayers by sputter depth profiling by Siegfried Hofmann (pp. 113-121).

Sputter depth profiling of nanostructures requires quantitative thin film analysis with high accuracy and with optimum resolution. More recently, powerful quantification models, such as the so-called mixing roughness information depth (MRI) model, have increased the accuracy of depth profiling to the sub-monolayer region. Using the MRI model, interdiffusion coefficients at nanolayer interfaces can be determined based on a mean diffusion path length of the order of 1nm. After summarizing the progress to date, focus is on new developments with respect to experimental improvements such as ultra-low ion energy and glancing incidence, cluster ion sputtering, and improvements in theoretical modeling and quantification of nonlinearities with respect to the intensity scale and to the time scale of a depth profile, and the change of important quantification parameters such as electron escape depth in AES and XPS, mixing length and roughness during profiling, particularly when sputtering through interfaces. Today, the accuracy of quantification of sputter depth profiles of layered nanostructures is typically about 20% of a monolayer, or 0.06nm on the elemental layer thickness scale.

Keywords: PACS; 68; 68.55.−a; 68.65.−kDepth profiling; Sputtering; Nanostructures; AES; SIMS

Quantitative evaluation of surface damage on SiO₂/Si specimen caused by electron beam irradiation by S. Tanuma; T. Kimura; K. Nishida; S. Hashimoto; M. Inoue; T. Ogiwara; M. Suzuki; K. Miura (pp. 122-126).

We have developed an accurate and easy method for the evaluation of electron beam damage of SiO₂ thin films on Si in Auger microprobe analysis. The critical dose of SiO₂ specimens can be determined from a curve fit with a proposed equation to the normalized measured metallic-like Si LVV peak intensities to that of a Si standard as a function of total electron dose. We found the inverse values of the resulting critical electron doses for 5% decomposition of SiO₂ thin films (10 and 100nm) on Si substrate are proportional to the electron stopping powers in the 3–15keV energy range.

Keywords: PACS; 82.80.Pv; 79.20.RfSurface damage; SiO; ₂; /Si; Electron beam irradiation; Stopping power; AES; Critical electron dose

Electron irradiation effect on depth profiling of a SiO₂/Si(100) surface by Auger electron spectroscopy by T. Yakabe; D. Fujita; K. Yoshihara (pp. 127-130).

Electron irradiation effect on depth profiling of a SiO₂/Si(100) surface has been studied. A theoretical model for electron stimulated desorption (ESD) and gas adsorption on the solid surface has been proposed. The ESD process on the solid surface has been evaluated by Auger electron spectroscopy (AES) combined with a depth profiling technique. Our model can explain the observed ESD effect in low electron current densities less than 30A/m². In higher current densities, the deviation from the model appears because dynamic diffusion process becomes dominant. Furthermore the dependencies of the ion sputtering rate and the depth resolution on the current density of the electron radiation have been observed quantitatively, whose origin has been discussed based on a model.

Keywords: PACS; 82.80.Pv; 82.20.Pm; 82.65.Yh; 61.80.Az; 61.80.−xAuger electron spectroscopy; Electron stimulated desorption; Adsorption; Ion sputtering rate; Depth resolution

Development of imaging energy analyzer using multipole Wien filter by H. Niimi; M. Kato; T. Tsutsumi; T. Kawasaki; H. Matsudaira; S. Suzuki; W.-J. Chun; Y. Kitajima; M. Kudo; K. Asakura (pp. 131-134).

We discussed a new design of a Wien filter energy analyzer for an energy-filtered X-ray photoemission electron microscopy system. We have demonstrated that the second-order aberration and the third-order aperture aberration can be corrected by the multipole Wien filter by adjusting multipole components of electric and magnetic fields up to octupole components. The three-dimensional charge simulation method indicated that 12 electrodes and magnetic poles can effectively reproduce these ideal electric and magnetic fields.

Keywords: PACS; 07.78.+s; 29.30.Dn; 42.15.FrdXPEEM; Wien filter; Multipole; Aberration correction

X-ray photoelectron spectroscopic analysis of HfO₂/Hf/SiO₂/Si structure by Ruiqin Tan; Yasushi Azuma; Isao Kojima (pp. 135-140).

A stoichiometric HfO₂ film was successfully prepared using direct reactive sputtering deposition on a native SiO₂/Si wafer, before which an ultrathin Hf metal film was deposited as a buffer layer. X-ray photoelectron spectroscopy depth profiling technique was employed to investigate the interface chemistry of the obtained structure. It was observed that Hf silicates were formed in the interfacial layer. The binding energies of Hf 4f and O 1s shifted to higher binding energy side synchronously during the removal of the contaminant layer. These shifts were attributed to the modification of the surface potential by Ar⁺ sputtering.

Keywords: PACS; 77.55.+f; 79.60.Jv; 81.15.Cd; 81.70.JbHafnium dioxide; X-ray photoelectron spectroscopy; Sputtering deposition; Depth profiling

Metastable-atom-stimulated desorption from dodecanethiolate self-assembled monolayers by Y. Yamauchi; T. Noro; M. Kurahashi; T. Suzuki; X. Ju (pp. 141-145).

The potential curves for the dissociation of dodecane cation are calculated in order to discuss the indirect mechanism of metastable-atom-stimulated desorption of CH_x⁺ from dodecanethiolate self-assembled monolayers. A single excitation configuration interaction method is used for drawing up the potential diagrams in two different reaction coordinates: CH and CC. The potential barrier height obtained for the ejection of CH₃⁺ was smaller than that of H⁺, suggesting that CH_x⁺ desorption can be triggered by the excitation of molecular orbitals even if a molecule is only locally stimulated.

Keywords: PACS; 31.25; 79.20.L; 79.20.R; 85.40.HCI; Potential curve; DIET; SAM; Metastable atom; Nanolithography

Characterization of alkanethiol/ZnO structures by X-ray photoelectron spectroscopy by K. Ogata; T. Hama; K. Hama; K. Koike; S. Sasa; M. Inoue; M. Yano (pp. 146-149).

1-Propanethiol (CH₃CH₂CH₂SH) was connected with O-polar zinc oxide (ZnO) surfaces toward biofunctional devices. X-ray photoelectron spectroscopy (XPS) measurement revealed that the SO bonds were formed between 1-propanethiol and ZnO layers. Although the surface coverage of the molecule is less than a few percent, 1-propanethiol/ZnO structures were stable even at thermal treatment of 400�C.

Keywords: PACS; 79.60.Fr; 81.07.PrOrganic–inorganic structure; ZnO; XPS; Thermal stability

Chiral metal surfaces from the adsorption of chiral and achiral molecules by V. Humblot; R. Raval (pp. 150-156).

Chiral surfaces, capable of existing in two distinguishable mirror forms that cannot be superimposed, are attracting worldwide attention. The adsorption of complex organic molecules provides a means of introducing the ultimate discrimination function of chirality to a metal surface. Here, a comparison of the chiral tartaric acid (HOOC–CHOH–CHOH–COOH) molecule and the achiral succinic acid (HOOC–CH₂–CH₂–COOH) molecule on a Cu(110) surface is presented. For both molecules, two-dimensional assembly is found to depend strongly on molecule–metal bonding interactions, whereas the presence/absence of the OH groups causes subtler, second-order effects on the self-assembled structure. The driving force for creating chiral organisations is shown to arise from adsorption-induced asymmetrisation, via molecular distortion and/or metal reconstruction of the local adsorption unit. The macroscopic chirality of the surface is then determined by whether nucleation points of both chirality can be equally created, or whether non-degeneracy can be introduced to favour one chirality.

Keywords: PACS; 68.43.−h; 87.15.ByChirality; Surfaces; Chemisorption; Carboxylates

Fabrication of nano-pits and the measurement of their local surface potentials by Michiko Yoshitake; Chandra Bose; Sinjiro Yagyu (pp. 157-163).

An Au(111) surface was irradiated with 500eV argon ions in a controlled manner to fabricate nano-pits. The surface morphology of nano-pits formed after 6ML removal by ion irradiation under various temperatures was studied with STM. The depth distribution of pits at various irradiation temperatures was analyzed. There was a specific irradiation temperature at which the depth of pits became very deep in comparison with other temperatures. The results were compared with other fcc metals. The local barrier height (LBH) on surfaces with pits was measured. The LBH images were compared with the topographic images. The width where surface potential was modified near steps was found wider than the topographic width of steps. For pits lager than the critical size, the LBH value at the bottom of pits was same as that on a flat terrace except at step edges.

Keywords: PACS; 81.65.CGold; Surface diffusion; Ion irradiation; Local barrier height; STM; Atomic step

Effects of surface cleaning on oxidation of NiAl(110) by Weijie Song; Michiko Yoshitake (pp. 164-168).

The effects of Ar⁺ ion sputtering on the surface of NiAl(110) and its oxidation behaviors were investigated using XPS and LEED. The surface roughness increased and the surface aluminium concentration decreased after several times of cleaning and oxidation of the NiAl(110) surface. This surface was shown to be less reactive under 1020K oxidation but more reactive under 500K than the first-cleaned NiAl(110) surface. After heating the samples with oxide over-layer to about 1320K for about 15min, the oxide over-layer was completely disappeared and a clean NiAl(110) surface was obtained. This result provided a new way to clean the NiAl(110) surface.

Keywords: PACS; 81.65.Mq; 61.14.Hg; 68.43.−hAlumina; NiAl(1; 1; 0); XPS; Surface cleaning

Estimation of adsorbed hydrogen on Ni(111) surface by slow-positron beam by Y. Oishi; T. Wada; I. Kanazawa; K. Fukutani; Y. Murata; Y. Ito; K. Nozawa; F. Komori (pp. 169-173).

We have measured reemitted slow-positrons from clean Ni(111) surface and hydrogen saturated one, and have observed the reduction of reemitted slow-positron by adsorbed hydrogen atoms in the case of saturated coverage. The origin of the reduction has been discussed, taking into account of electrostatic repulsion between hydrogen adatoms.

Keywords: PACS; 34.50.Dy; 68.49.−h; 34.85+xAdsorbed hydrogen; Ni surface; Reemitted slow-positrons

Pattern formation induced by Ar⁺ sputtering on Au(111) by A. Chandra Bose; M. Yoshitake (pp. 174-178).

Ion sputtering is employed to produce structures on the nanometer scale. The surface morphology of Au(111) after sputtering with 500eV Ar⁺ ions at various sputtering temperatures (from room temperature (RT) to 150�C with variation of 25�C) has been investigated by scanning tunneling microscopy (STM). It is shown that the sputtering temperature can be used to determine the final surface morphology. At all sputtering temperatures, the surface is characterized by random distribution of pits. The shape and size are briefly discussed. The obtained surface morphology is explained with diffusion processes at various sputtering temperatures. The final surface morphology is the result of the diffusion processes.

Keywords: PACS; 79.20.R; 61.16.C; 68.35.FScanning tunneling microscopy; Surface morphology; Sputtering; Surface diffusion

Effect of evaporation on surface morphology of epitaxial ZnO films during postdeposition annealing by I.W. Kim; S.J. Doh; C.C. Kim; Jung Ho Je; J. Tashiro; M. Yoshimoto (pp. 179-182).

We investigated the effect of evaporation on the surface morphology of c-oriented epitaxial ZnO (40nm thick)/Al₂O₃(0001) films during postdeposition annealing using real time synchrotron X-ray scattering and atomic force microscopy (AFM). We find that evaporation as well as grain coalescence play crucial roles on the surface morphology of the ZnO/Al₂O₃(0001) films. Grain growth occurring in initial stage of annealing forms facets with higher surface energies than the (0001) planes. By the preferential evaporation of the prism planes, the surface morphology of the ZnO film eventually evolves into 2D flat (0001) surface at 800�C, as confirmed by AFM. The real time measurement of the film thickness during annealing also supports the effect of the evaporation on the morphology. The evaporation rate is high in initial stage by the preferential evaporation from high energy facets but slows down after transition to the flat (0001) surface.

Keywords: PACS; 68.43.Vx; 68.35.Md; 68.35.−p; 61.10.Nz; 68.55.AcZnO; Evaporation; Annealing; Surface morphology

Thermal stability of succinate and acetate on a Cu(110) surface by S. Yagyu; M. Yoshitake; T. Chikyow (pp. 183-188).

We made a helium atom beam scattering (HAS) apparatus to study the thermal dynamics of adsorbed organic molecules on a surface. The apparatus had an angular resolution of 6° and energy resolutions of 20%, with an incident energy of E_i=63meV. We measured the thermal stability of acetic acid (CH₃–COOH) and succinic acid (HOOC–CH₂–CH₂–COOH) structures on a Cu(110) using the DW-plot technique (the temperature variation of intensity of the He beam specularly reflected from the surface). We found that the desorption temperatures derived from DW-plots are 540K for low-coverage acetate, 550K for c(2×2) acetate and 590K at succinate. The desorption temperature of succinate is higher than acetate, which is interpreted by a larger number of carboxylates in one molecule.

Keywords: PACS; 34.50.DyCopper; Carboxylic acid; Temperature programmed desorption; Helium atomic beam scattering

Tunneling-current-induced reaction of mercaptobutanol on Au(111) by K. Tsukamoto; H. Nozoye (pp. 189-193).

Tunneling-current-induced reaction in self-assembled monolayers of mercaptobutanol (HS(CH₂)₄OH:C4OH) has been investigated using ultra-high vacuum scanning tunneling microscopy (STM). Two different reaction channels (decomposition and translation of molecules) were observed depending on the coverage of C4OH. The threshold tunneling bias voltages of the two reaction channels are the same, ±2.5V. The possible channels for decomposition and translation of molecules are the rupture of the C–S bonding and the local heating of the ensemble of C4OH, respectively.

Keywords: PACS; 61.16.CScanning tunneling microscopy; Self-assembled monolayers; Organic thin films; Lithography; Reaction

Characterization and control of molecular ordering on adsorbate-induced reconstructed surfaces by Woei Wu Pai; C.L. Hsu; K.C. Lin; L.Y. Sin; Tong B. Tang (pp. 194-198).

Understanding molecular ordering is a critical step in achieving molecular self-assembly for the fabrication of nanomaterials, and molecular ordering in the adsorption of large molecules on atomically flat surfaces can be characterized with precision by scanning tunneling microscopy (STM). Complications arise therein from the expanded possibility of various adsorption structures, conformations and surface reconstructions. Here we present two cases of C₆₀ adsorbed on Ag(100) and Cu(111) that illustrate the importance of competitive interactions in the presence of adsorbate-induced reconstruction. In both studies, strong STM contrasts derive from topographic features arising from reconstructed substrates. C₆₀/Ag(100) presents a unique uniaxially incommensurate molecular packing. We have also found that one can control molecular ordering with a stepped surface to produce a single-domain film. In C₆₀/Cu(111), we are able to obtain metastable, yet well-defined, molecular ordering with precise annealing procedures. These metastable states exhibit a clear correlation between molecular contrast patterns and the adlayer rotation angle, as a consequence of competitive interactions between optimizing C₆₀ bonding at preferred reconstructive sites and C₆₀–C₆₀ repulsion. Finer control of selective preparation of these metastable structures offers a plausible way of fabricating nanostructures by design.

Keywords: PACS; 68.43.−h; 68.43.Fg; 68.37.Ef; 64.60.MyFullerenes; Surface reconstruction; Surface steps; Incommensurate structure; Scanning tunneling microscopy

X-ray absorption near edge structure of small FePt atomic clusters by Sher Alam; Javed Ahmed; Yoshio Matsui (pp. 199-204).

X-ray absorption near edge structure of small FePt atomic clusters has been studied using a full multiple scattering, a self-consistent field, and the real-space Green’s function approach realized via the ab initio FEFF8.20 code. We show theμ difference spectra of the Pt L3 edge with respect to the size and shape of the small FePt atomic clusters. The difference spectra at the Fe L3 edge also shows variation, but is less pronounced as compared with the results from the Pt L3 edge. Calculations are made with and without core-hole. It is shown that the white line intensity is reduced for both the Pt and Fe L3 edges with the core-hole. In the case of Pt L3 edge the shape of the spectra without the core-hole agrees much more closely with the experimental results.

Keywords: PACS; 78.20.; −; e; 78.30.; −; j; 74.76.BzXANES; SCF; FEFF8.20; Ab initio

Preparation of Coumarin 6 and ZnTPP micro dots on PBMA films by laser molecular implantation by Y. Pihosh; T. Oishi; M. Goto; A. Kasahara; M. Tosa (pp. 205-208).

A pulsed dye laser was used to implant Coumarin 6 (C6) and tetraphenyl-porphine zinc functional organic molecules (ZnTPP) into poly (butyl methacrylate) (PBMA) polymer films. The resulting films were patterned with a matrix of well-formed dots several micrometers in diameter. The dependence of the size of implanted dots on the laser intensity has been studied at different concentrations of the dopants in the source films. The mass distribution of each particular dot on PBMA target film was inferred using the fluorescence intensity distribution of the implanted dots. The dependence of the lower and upper limits of the dot's size was determined when source films having different dopant concentrations were used. Based on the results obtained the optimum parameters for creation of extended “two colour�? complex patterns consisting of both, C6 and ZnTPP, molecular dots were established.

Keywords: PACS; 81.15.F; 36.40; 79.20.D; 42.82.CLaser molecular implantation; Coumarin 6; Tetraphenyl-porphine zinc; Fluorescence molecule; Polymer; Micro-pattering

Characterization of binary gold/platinum nanoparticles prepared by sonochemistry technique by M. Nakanishi; H. Takatani; Y. Kobayashi; F. Hori; R. Taniguchi; A. Iwase; R. Oshima (pp. 209-212).

Aqueous solutions with Au³⁺and Pt⁴⁺ ions and additives of surfactants (SDS or PEG-MS) were irradiated with an ultrasound at 200kHz with an input power of 4.2W/cm², and colloidal nanoparticles were prepared. The prepared nanoparticles were characterized by XRD, TEM, HRTEM, EDX and¹⁹⁷Au Mössbauer spectroscopy. It was found that the structures of nanoparticles were changed with the surfactants; Au and Pt nanoparticles were prepared individually by using SDS, and bimetallic Au/Pt alloy nanoparticles with a core–shell structure were produced in the presence of PEG-MS.

Keywords: PACS; 61.46.+wSonochemistry; Gold–platinum alloy; Nanoparticle; Core–shell structure; HRTEM; ¹⁹⁷; Au Mössbauer spectroscopy

Optical monitoring of nanoparticle formation during negative 60keV Cu ion implantation into LiNbO₃ by O.A. Plaksin; Y. Takeda; H. Amekura; N. Umeda; K. Kono; N. Okubo; N. Kishimoto (pp. 213-217).

Spectra of the optical transmission and ion-induced photon emission (IIPE) of LiNbO₃ were measured during implantation of 60keV Cu⁻ ions at ion fluxes from 1 to 50μA/cm² up to a fluence of 2×10¹⁷ions/cm². The optical transmission in the range of surface plasmon resonance (SPR) and the IIPE are good monitors of the nanocomposite formation and the chemical composition change, respectively. Copper atoms precipitate at fluences lower than 6×10¹⁵ions/cm². Further formation of nanocomposite comprises two easily distinguishable stages: the slope of fluence dependencies of SPR abruptly decreases at about 10¹⁷ions/cm². Lithium-depleted regions are created in the substrates, and concentration of Nb increases. The formation of nanocomposite is most efficient at a flux of 1μA/cm².

Keywords: PACS; 61.46.; +; w; 78.67.; −; n; 81.07.Bc; 81.16.; −; cHeavy-ion implantation; Metal nanoparticles; Lithium niobate; In situ optical transmission; Ion-induced photon emission

Size-controlled synthesis of nickel nanoparticles by Y. Hou; H. Kondoh; T. Ohta; S. Gao (pp. 218-222).

A facile reduction approach with nickel acetylacetonate, Ni(acac)₂, and sodium borohydride or superhydride leads to monodisperse nickel nanoparticles in the presence of hexadecylamine (HDA) and trioctylphosphine oxide (TOPO). The combination of HDA and TOPO used in the conventional synthesis of semiconductor nanocrystals also provides better control over particle growth in the metal nanoparticle synthesis. The size of Ni nanoparticles can be readily tuned from 3 to 11nm, depending on the ratio of HDA to TOPO in the reaction system. As-synthesized Ni nanoparticles have a cubic structure as characterized by power X-ray diffraction (XRD), selected-area electron diffraction (SAED). Transmission electron microscopy (TEM) images show that Ni nanoparticles have narrow size distribution. SQUID magnetometry was also used in the characterization of Ni nanoparticles. The synthetic procedure can be extended to the preparation of high quality metal or alloy nanoparticles.

Keywords: PACS; 81.05.Y; 75.50.K; 61.46Synthesis; Nickel; Nanoparticles; Magnetism

Silicon microstructure fabricated by laser micro-patterning method combined with wet etching process by T. Oishi; M. Goto; Y. Pihosh; A. Kasahara; M. Tosa (pp. 223-226).

A simple method for silicon microfabrication has been successfully developed. Polypropylene (PP) film as a resist was prepared on a surface of silicon (Si) (100) plate by an rf magnetron sputtering method. A pulsed laser light was focused and irradiated to the PP film and a part of the film was removed by laser ablation process in the spot at certain laser intensity. When the sample was immersed in a potassium hydroxide solution, etching occurred only at the part that the PP film was removed by laser ablation. These results raise the possibility of this method as a process for Si microfabrication.

Keywords: PACS; 85.40.HpMicrofabrication; Silicon; Micro-machine; Micro-patterning; Laser ablation

Particle size distribution analysis for nano-SiO₂ powder by ultra-small angle X-ray scattering (USAXS) using synchrotron radiation by Hisayuki Hashimoto; Toshiaki Nagumo; Tohru Inaba; Yoichiro Furukawa; Masato Okui; Sei Fukushima (pp. 227-230).

Ultra-small angle X-ray scattering (USAXS) experiments were conducted with the BL15XU beamline (SPring-8) to perform a particle size distribution analysis of nano-powder, i.e. aggregations of particles with dimensions on the order of nanometers. The samples measured were amorphous nano-SiO₂ powders of varying specific surface areas. Since a highly collimated and high-intensity X-ray beam is available, it is possible to obtain USAXS spectra that are only slightly affected by background noise. The USAXS spectra obtained from nano-SiO₂ powders were analyzed by a modified Fankuchen technique, a method for particle size distribution analysis adapted by the authors. Using this technique, particle size distribution measurements can be performed over a wide range of particle diameters from 1 to 200nm. Since this method enables the particle size distribution of nano-powder to be accurately and easily determined, it is expected to be useful in a wide variety of fields.

Keywords: PACS; 07.85.Qe; 81.07.WxNano-powder; Ultra-small angle X-ray scattering (USAXS); Particle size distribution; Modified Fankuchen technique; Synchrotron radiation; SPring-8

Microstructures and IR spectra of long amorphous SiO₂/Si nanowires by T. Noda; H. Suzuki; H. Araki; W. Yang; Ying Shi; M. Tosa (pp. 231-235).

Long Si nanowires were tried to form using a thermal gradient evaporation method. Amorphous SiO₂/Si nanowires longer than 6mm were formed at 1403–1433K. The long nanowires consist of a silicon single core of 50–100nm in diameter and an amorphous SiO₂ outer layer of 10–15nm in thickness. The growth direction of the long Si nanowires was 〈111〉. The nanowires showed IR absorption peaks at 1130, 1160 and 1200cm⁻¹ due to the disordered structure of SiO₂/Si nanowires.

Keywords: PACS; 60; 61.82.RxAmorphous SiO; ₂; /Si nanowires; Thermal gradient evaporation method; IR spectrum

In situ synthesis and characterization of pure SiC nanowires on silicon wafer by W. Yang; H. Araki; S. Thaveethavorn; H. Suzuki; T. Noda (pp. 236-240).

A simple template/catalyst-free chemical vapor growth process was developed for growing SiC nanowire directly on silicon wafers. The nanowires were identified as single crystalline β-phase SiC growing along <111> direction. The nanowires possess Si–C chemistry. The length and thickness of the nanowires are generally from several tens to over 100μm and ∼80nm, respectively. The process also demonstrated the possibility of in situ deposition of thin graphite coatings on the SiC nanowires. A contribution of present work to the applications of SiC nanowires, especially as reinforcement materials in ceramic nanocomposites, is expected.

Keywords: PACS; 60; 61.82.RxSiC nanowires; Chemical vapor growth; In situ graphite coating

Fabrication of a gold pattern with a nanoscale edge by using heptanethiol self-assembled monolayers and a metastable helium beam by X. Ju; M. Kurahashi; T. Suzuki; Y. Yamauchi (pp. 241-245).

By exposure to a metastable helium beam, latent images of the patterns were formed in the heptanethiol (HT) self-assembled monolayer (SAM) resists on Au(111) films, and then the patterns were transferred to the underlying gold films by wet chemical etching. Negative patterns, as well as positive patterns with lower doses, were fabricated with higher exposures to a metastable-atom beam. The smallest width of edge, ∼40nm, among alkanethiol SAM resists was achieved in the condition of negative pattern formation. According to the metastable-atom-stimulated desorption (MSD) measurement of alkanethiol SAMs on Au(111), the SAMs were damaged under the irradiation of metastable-atom beam losing either H atoms or CH₃ groups. Thus, the highly concentrated energy deposition by a metastable-atom beam, which induced crosslinking of the main molecular chain in the SAM resists and increased the resistance to etching, could lead to the negative pattern formation at higher doses.

Keywords: PACS; 81.16.Nd; 81.16.Dn; 61.80.LjMetastable atom; Self-assembled monolayers; Heptanethiol

B–C–N hybrid synthesis by high-temperature ion implantation by Md. Nizam Uddin; Iwao Shimoyama; Yuji Baba; Tetsuhiro Sekiguchi; Krishna G. Nath; Masamitsu Nagano (pp. 246-249).

In order to synthesize B–C–N hybrid thin films, borazine (B₃N₃H₆) ion plasma was implanted in graphite at room temperature (RT) and 600°C. The X-ray photoelectron spectroscopy (XPS) study suggested that B atoms in the deposited films are in a wide variety of atomic environment such as BC₃, BN₃ and B–C–N hybrid. The ratios of these coordinations strongly depend on the temperature during the ion implantation. It was found that the B–C–N hybrid is predominantly synthesized by the implantation at 600°C where the surface [B]/([B]+[C]+[N]) ratio ranges from 0.1 to 0.35. The results imply that it is possible to control the composition of B–C–N hybrid by changing the fluence of the ion plasma and the temperature of graphite during ion implantation.

Keywords: PACS; 81.15.Jj; 33.60.FyBoron carbon nitride; X-ray photoelectron spectroscopy; Ion implantation

Formation of epitaxial Al₂O₃/NiAl(110) films: aluminium deposition by Y. Lykhach; V. Moroz; M. Yoshitake (pp. 250-255).

Structure of epitaxial Al₂O₃ layers formed on NiAl(110) substrates has been studied by means of reflection high-energy electron diffraction (RHEED). The elucidated structure was compared to the model suggested for 0.5nm-thick Al₂O₃ layers [K. M�ller, H. Lindner, D.M. Zehner, G. Ownby, Verh. Dtsch. Phys. Ges. 25 (1990) 1130; R.M. Jaeger, H. Kuhlenbeck, H.J. Freund, Surf. Sci. 259 (1991) 235]. The stepwise growth of Al₂O₃ film, involving deposition and subsequent oxidation of aluminium onto epitaxial 0.5nm-thick Al₂O₃ layers, has been investigated. Aluminium was deposited at room temperature, whereas its oxidation took place during annealing at 1070K. The Al₂O₃ thickness was monitored by means of Auger electron spectroscopy (AES). It was found that Al₂O₃ layer follows the structure of 0.5nm thick Al₂O₃ film, although a tilting of Al₂O₃(111) surface plane with respect to NiAl(110) surface appeared after Al deposition.

Keywords: PACS; 68.55.Jk; 81.15.−z; 61.14HAluminium deposition; Al; ₂; O; ₃; Epitaxy; RHEED

First steps in the growth of Cu thin films on the five-fold surface of the icosahedral Al–Cu–Fe quasicrystal by H.R. Sharma; M. Shimoda; V. Fourn�e; A.R. Ross; T.A. Lograsso; A.P. Tsai (pp. 256-260).

The growth of Cu on the five-fold surface of the icosahedral Al–Cu–Fe is investigated by scanning tunneling microscopy. The clean surface exhibits atomically flat terraces separated by steps of different heights. The steps are found to be frequently bunched. For a coverage close to a monolayer, Cu forms a nearly closed film of a height corresponding to a monolayer of Cu. The film, however, does not exhibit long-range order.

Keywords: Scanning tunneling microscopy; Epitaxy; Metallic surfaces; Copper; Alloys

Effect of ultra-thin buffer on the structure of highly mismatched epitaxial ZnO during sputter growth by I.W. Kim; H.S. Kim; Y.B. Kwon; S.J. Doh; C.C. Kim; Jung Ho Je; P. Ruterana; G. Nouet (pp. 261-265).

We investigated the microstructural evolution of ZnO/Al₂O₃(0001) films with and without an ultra-thin (4nm) ZnO buffer that was grown at a low temperature (LT) of 300�C using real time synchrotron X-ray scattering, atomic force microscopy, and high resolution electron microscopy. It is shown that the ultra-thin two-dimensional (2D) layers play a critical role for improving the ZnO layer quality, by inducing 2D growth mode instead of 3D mode at 500�C in early stage. The ZnO films grown on the ultra-thin buffer exhibited structural coherence between the surface and the interface in the substrate normal direction in early stage. The great enhancement of the structural quality was attributed to the strain accommodation by the 2D ultra-thin buffer.

Keywords: PACS; 68.55.Ac; 68.55.Jk; 68.37.LpZnO; Sapphire; Low temperature Buffer; Strain

Formation of isotope controlled SiC thin film by plasma chemical vapor deposition and its characterization by H. Suzuki; H. Araki; W. Yang; T. Noda (pp. 266-269).

Formation of isotope controlled SiC thin film by plasma chemical vapor deposition has been examined with SiF₄ and CH₄ and characterization of film was performed. From scanning electron microscope observation, the surface of film showed fine granular morphology and the cross section view of film showed a pillar-shaped structure. The X-ray diffraction measurement showed that thin film consisted of polycrystalline 3C–SiC. The crystallinity and crystalline diameter of microcrystalline thin film increased with substrate temperature and reached maximum value at 1023K. At higher temperature, crystallinity and crystalline diameter decreased.

Keywords: PACS; 80;81.15.GhSiC thin film; Plasma chemical vapor deposition

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Applied Surface Science (v.241, #1-2)