Atsushi Koma

The University of Tokyo | Todai · Faculty of Science and Graduate School of Science

Epitaxial thin film multilayers are limited by the need for both lattice and thermal expansion matching. Recently, a new deposition technique, known as van der Waals epitaxy , has been developed to overcome these limitations. Van der Waals Epitaxy (VDWE)promises the ability to deposit multilayers based on the property of interest without being limi...

A highly insulating CaF2 surface was investigated by Auger electron spectroscopy (AES) and electron energy loss spectroscopy (EELS). Reduction of primary electron current could suppress the surface deterioration during electron spectroscopy, which enabled the AES measurement of a stoichiometric CaF2 surface for the first time. Combination of AES an...

The interaction between pentacene molecules and organic self-assembling monolayers formed on silicon oxides (SiO2) was studied by measuring the surface scattering time profile of the pulsed molecular beam of pentacene. It was found that the surface residence time (SRT) of pentacene was significantly reduced on a surface treated with hexamethyl sila...

Thin films of C60 were grown under laser irradiation at various intensities 0–200 mW∕mm2 and their growth shapes were investigated by ex situ atomic force microscopy (AFM) observation. The nucleation density of the first layer decreases with increasing laser intensity, probably due to the temperature rise of the migrating clusters. In addition to t...

We studied the effect of a direct electric field with an intensity gradient during the thin film deposition of liquid crystal molecules under ultrahigh vacuum. Alignment of elongated islands was observed when the electric field was higher than the threshold value of 4×105 to 5×106 Vm−1, which was dependent on the substrate temperature. Layer-by-lay...

Ultraviolet photoelectron spectroscopy of epitaxial films of squaric acid (H2C4O4), a two-dimensional antiferroelectric organic material, is reported. The band structure parallel to the two-dimensional molecular plane was derived, in which the dispersion of the HOMO-2 band was found to be as large as 0.7 eV. The molecular orientation was estimated...

Ultraviolet photoelectron spectroscopy (UPS) of C60 thin-film field-effect transistors was measured with biasing gate voltages. A time-dependent change in the electronic structure of the C60 film was observed during the UPS measurement, which has never been observed in a C60 film grown on a conductive substrate. The change was attributed to the acc...

Methyl-terminated Si(111) (Me–Si(111)) and bilayer-GaSe terminated Si (BGS) surfaces were investigated to explore their usefulness as the protection layer in the fabrication process of nanometer-scale self-assembled monolayers (SAMs). BGS was not stable in the reagent involved in the alkyl SAM formation, whereas Me–Si(111) was suitable for the prot...

LiBr/Si(001) heterostructure has been investigated by scanning tunneling microscopy and spectroscopy (STM and STS). In the initial stage of LiBr growth, rectangular islands are observed consisting of accumulation of about 0.2 nm-thick unit layers. The STM results indicate that LiBr grows on Si(001) in a single layer fashion. The STS measurement sho...

CsCl has been known to show extraordinary photoemission by visible (VIS) light only after ultraviolet (UV) light irradiation. To elucidate this phenomenon, photo yield and photoemission spectrum of a single-crystalline CsCl thin film were measured in ultrahigh vacuum. Photo yield measurements confirmed that photoelectrons were emitted from F-center...

Atomic and electronic structures of a polar surface of MgO formed on Ag(111) was investigated by using reflection high-energy electron-diffraction, Auger-electron spectroscopy, electron energy-loss spectroscopy (EELS), and ultraviolet photoemission spectroscopy (UPS). A rather flat unreconstructed polar MgO(111) 1×1 surface could be grown by altern...

It was found that electrochemical deposition of copper from a [Cu(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline)2]+ ([Cu(bcp)2]+) complex can be induced by photoirradiation at a certain cathode potential. It can be used for photopatterning of copper and controlling electrodeposition of copper in microelectronics applications. The mechanism of the p...

Breakdown properties of thin insulating films of LiF were studied by the 2-probe method in vacuum. A LiF film was found to grow heteroepitaxially on a Ag(001) substrate at 700 K, while an amorphous LiF film grew at room temperature. The breakdown strength depended on the crystallinity of LiF, but was not related to the film thickness. The single-cr...

In order to search for states specific to insulator/metal interfaces, we have studied epitaxially grown interfaces with element-selective near edge x-ray absorption fine structure. An extra peak is observed below the bulk edge onset for LiCl films on Cu and Ag substrates. The nature of chemical bonds as probed by x-ray photoemission spectroscopy an...

We use real-time measurement of substrate curvature and reflection high energy electron diffraction (RHEED) methods to observe the film stress/strain behavior during epitaxial growth of Sr metal films and their oxidation process. The film stress and the thickness of the strained layer are minimized by using hydrogen-terminated Si substrates. The us...

Interferometric microscopy was used to observe the initial stage of the crystal growth of an organic charge transfer salt (DMe-DCNQI)2Cu by electrochemical reaction. It was found that concentric patterns started to appear after applying the potential difference between the electrodes. Bright rings of the concentric pattern moved outward for about 1...

A single crystalline LiCl film grows heteroepitaxially on Cu(0 0 1) in a layer-by-layer fashion at 300 K. The LiCl–Cu(0 0 1) system provides a well-defined insulator–metal interface. Electronic structure of the LiCl film grown on Cu(0 0 1) was studied using Cl K-edge near edge X-ray absorption fine structure (NEXAFS). A pre-peak was observed on the...

Thin film growth and electronic structure of C60 on Ni(111) and Cu(111) were studied by reflection high-energy electron diffraction (RHEED) and electron energy loss spectroscopy (EELS). A single-crystalline C60 film is found to grow heteroepitaxially on Ni(111) with a 4×4 structure. The EELS results show peak broadening and energy shifts of π-plasm...

Thin films of ionic compounds of ZnS clusters were measured by electron energy loss spectroscopy (EELS) and ultraviolet photoelectron spectroscopy (UPS). A size effect was observed in the valence plasmon energy measured by EELS from which the coherence length of the plasmon excitation can be estimated. The difference between the lowest excitations...

Angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) of a Si(1 1 1) surface regularly terminated by methyl groups is reported. The electrochemical methylation was performed in inert atmosphere. The cleanliness and 1×1 ordering of the surface were confirmed by Auger electron spectroscopy and reflection high-energy electron diffraction, resp...

Epitaxial growth of CoO films was studied using reflection high-energy electron diffraction (RHEED), electron energy loss spectroscopy (EELS), ultraviolet photoelectron spectroscopy (UPS) and Auger electron spectroscopy (AES). The RHEED results indicated that an epitaxial CoO film grew on semiconductor and metal substrates (CoO (001)∥GaAs (001), Cu...

Atomic and electronic structures of CsBr films grown on LiF(0 0 1) and KBr(0 0 1) were studied by reflection high energy electron diffraction, electron energy loss spectroscopy (EELS) and ultraviolet photoelectron spectroscopy (UPS). On a LiF(0 0 1) substrate, an α-CsBr film with a cesium chloride structure grew heteroepitaxially at 300 K, while a...

Electronic structure of the heteroepitaxial LiCl thin film grown on Cu(0 0 1) was studied using electron energy loss spectroscopy (EELS) and ultraviolet photoelectron spectroscopy (UPS), as a model system of the insulator/metal interface. The EELS results did not show any change in the band gap of the LiCl film, though the Anderson’s prediction ind...

We use real-time measurement of substrate curvature to observe the film stress behavior during epitaxial growth of Sr metal films and their oxidation process at room temperature. The lattice mismatch stress and the thickness of strained layer are controlled to be minimized by using hydrogen-terminated Si whose surfaces have no active dangling bonds...

Thin-film growth of alkali halides on (001) surfaces of fcc transition metals was studied using reflection high-energy electron diffraction. Alkali halide grew with its [100] axis rotated by 45° from that of the metal substrate ([100]film//[110]substrate) for LiCl/Cu(001) and LiCl/Ni(001). On the contrary, alkali halide grew without azimuthal rotat...

The characteristics of interaction between a monolayer C60 epitaxial film and a Si(1 1 1)-7×7 surface have been studied using electron energy loss spectroscopy (EELS). The EELS measurement in the π–π* transitions region indicates that the interaction between C60 molecules and the Si(1 1 1)-7×7 surface largely modifies the electronic structure of a...

Nano-scale oxide patterns were fabricated on a bilayer-GaSe terminated Si(1 1 1) surface using an atomic force microscope (AFM) in air. The Si(1 1 1) surface regularly terminated by bilayer-GaSe is very stable in air, although it can be oxidized through the electrochemical reaction when positive sample bias voltage is applied between the surface an...

Thin film growth of MgO on Ag(0 0 1) was studied using reflection high-energy electron diffraction, Auger electron spectroscopy, electron energy loss spectroscopy (EELS), and ultraviolet photoemission spectroscopy (UPS), as a model system of the oxide/metal interface. At a substrate temperature of 450 K, a single-domain MgO film ([1 0 0]film//[1 0...

The prospects of electron spectroscopy of working organic electronic device structures are discussed. The experimental consideration and the result of actual measurement are presented.

As a stable and ‘epitaxial’ passivation of a Si surface, we propose the bilayer-GaSe termination of a Si(111) surface. This surface is fabricated by depositing one monolayer of Ga on a clean Si(111) surface and subsequent annealing in a Se flux at around 520°C, which results in unreconstructed 1×1 termination of the Si(111) surface by bilayer-GaSe....

Electron spectroscopy experiments were attempted to the measure the electronic structure of organic field effect transistors (FETs) under a gate bias. Sample structure, experimental condition and results of FETs made of C60 are described. C60 FET structures showed irreversible change of the valence spectra during the ultraviolet photoelectron spect...

Interatomic potential of ionic bonds in alkali halide solid solutions has been studied by temperature dependent EXAFS (extended X-ray absorption fine structure). As a typical ionic bond in alkali halide solid solutions, K-Br bond of KCl0.8Br0.2 and KBr0.2I0.8 solid solutions have been focused. The K-Br bond was contracted for KCl0.8Br0.2, while it...

Heteroepitaxial growth of alkali halide solid solution on GaAs(100) was studied using reflection high-energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectroscopy. In past studies, a higher substrate temperature has been needed for the epitaxial growth of alkali halides on semiconductor substrates. We could grow a...

Heteroepitaxial growth of LiF on LiBr or NaCl has been investigated by using reflection high-energy electron diffraction, Auger electron spectra, electron energy loss spectra and ultraviolet photoelectron spectra. In the case of LiF on LiBr, [100] axis of LiF is parallel to [110] axis of LiBr, while LiF grows on NaCl with [100]LiF∥[100]NaCl. The az...

We have fabricated a vacancy-ordered Ga 2Se 3 epitaxial film by molecular beam epitaxy on a vicinal Si(0 0 1) surface tilted toward the [1 1 0] direction by 4°. It was found by reflection high-energy electron diffraction observations that Ga 2Se 3 films grown around 470°C with Se/Ga flux ratios higher than 100 show excellent ordering of Ga vacancie...

New-type nanostructures of organic molecules and inorganic semiconductors have been successfully fabricated on 'inactive' substrate surfaces such as layered material surfaces and dangling-bond terminated semiconductor surfaces. In this article we introduce two examples of our methods. One is the fabrication of C_<60> molecular nanostructures on a G...

Monolayer and multilayer LaatC82 films were epitaxially grown on MoS2 substrates, and their growth features together with electronic states were investigated using atomic force microscopy and electron energy loss spectroscopy. It was found that the interaction between a LaatC82 molecule and a MoS2 surface is stronger than that between LaatC82 molec...

Growth of NiO films was examined on various crystal faces of GaAs by using a single electron bombardment source. Use of alkali halide buffer layers achieved good quality of epitaxial growth on GaAs (001). Electron spectroscopies (Auger electron spectroscopy, ultraviolet photoelectron spectroscopy, electron energy loss spectroscopy) revealed that th...

We demonstrate and analyze the epitaxial film formation of a molecular material that cannot be evaporated in vacuum due to thermal decomposition. A solution of the material is sprayed onto single crystalline van der Waals surfaces using a pulse valve under controlled vapor pressure of the solvent. Monolayer epitaxial films are obtained and we propo...

The effect of impurity atoms on the surface electronic structure of semiconducting transition metal dichalcogenides, MoS2 and MoSe2, has been investigated by a scanning tunneling microscope (STM) and by its spectroscopic mode, scanning tunneling spectroscopy. The following impurity atoms have been studied: (1) alkali metal atoms deposited by using...

Thin film growth of LiCl on a Cu(001) substrate is studied using reflection high-energy electron diffraction and Auger electron spectroscopy. A LiCl film was found to grow heteroepitaxially on a Cu(001) substrate. At a substrate temperature of 300 K, a single-domain LiCl film ([100]film//[110]substrate) grows in a layer-by-layer fashion, while a do...

We have developed a novel method to fabricate self-assembled quantum dots (QDs) of compound semiconductors on a Si(111) substrate using the so-called `droplet epitaxy' technique. In order to fabricate QDs on a Si substrate by droplet epitaxy, we examined the termination of a Si (111) surface with a bilayer-GaSe. This surface is formed by depositing...

Kinetics of epitaxial thin film growth was analyzed from the experiments using pulsed organic molecular beams. It was found that a minimum appears in the nucleation density as a function of on-off cycle time when the substrate temperature is near the threshold between growth and reevaporation. This feature can be explained by assuming desorption of...

Ordered films of tris-8-hydroxyquionolate-aluminum (Alq3) were grown by molecular beam deposition on cleaved KCl and KBr surfaces. The local molecular arrangements in the films were characterized by two-dimensional analysis of multiazimuth reflection medium energy electron diffraction (RMEED). A new type of curved one-dimensional crystallographic o...

We have investigated the electronic structure of KxC60 (x=0–6) using low-energy electron energy loss spectroscopy (LEELS), especially focusing on the K3p core-electron excitation spectra. It is found that the structure of the K3p-excitation spectrum of KxC60 quite differs from that of KCl. Furthermore, the K3p-excitation LEELS of K3C60 has been rev...

Initial oxidation process of Mg films was investigated by Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS) and ultraviolet photoelectron spectroscopy (UPS). A polycrystalline Mg film was exposed to oxygen at room temperature. An inspection of EELS reveals that the initial oxidation process could be classified according to...

The characteristics of interaction between C60 molecules and Si(111)-7×7, Ag/Si(111)-√3×√3 R30° and layered material MoS2 surfaces have been investigated using electron-energy-loss spectroscopy (EELS). The EEL spectrum of C60/Si(111)-7×7 shows a new peak at loss energy of 2.7eV. This indicates the existence of charge transfer from the substrate to...

The initial stage of heteroepitaxial growth of alkali halide on other alkali halide was studied using reflection high energy electron diffraction, electron energy loss spectroscopy and Auger electron spectroscopy. The lattice distortion relaxed more rapidly for the system where the lattice constant of the film was larger than that of the substrate...

Pulsed molecular beam scattering technique was applied to analyze the dynamics of a large planar molecule migrating on various surfaces (Au(111), graphite(0001), mica (001), amorphous silicon oxide). It was found that molecules can stay on the surface for seconds without condensation. Activation energies have a magnitude comparable to those of a si...

Sub-monolayer films of layered semiconductor InSe were grown on MoS2 substrates by molecular beam epitaxy, and the change in their growth features with Se/In flux ratio was investigated using scanning tunneling microscope in vacuum. It was found that InSe domains grown at 340°C have a hexagonal shape when the Se/In ratio is about 17. Detailed image...

Molecular arrangement and electronic structure of a La@C82 film epitaxially grown on an MoS2 surface have been studied using reflection high-energy electron diffraction and electron energy-loss spectroscopy (EELS). It was revealed that La@C82 molecules form a close-packed hexagonal lattice on a cleaved face of MoS2 with the intermolecular distance...

Micro-channel plate (MCP) was used to intensify the image on the fluorescent screen in reflection high-energy electron diffraction. The primary electron current could be reduced by four orders of magnitude to get the image of the same intensity as in the measurement without MCP. The reduction of electron beam enabled observation of ionic crystal su...

The temperature and doping dependences of photoemission spectra of polycrystalline HgBa2CuO4+δ samples are investigated for several doping levels near the optimum (Tc=98K). As doping increases, we observed a systematic shift of the core levels and an increase in the density of states at the Fermi level (EF). Nonlinear shifts of the core levels with...

Epitaxial growth of SrO films on hydrogen-passivated Si (100) surfaces has been demonstrated. The hydrogen-passivated Si, whose surface dangling bonds are saturated with hydrogen atoms, is chemically inactive, especially against oxidation. The alternate supply of Sr and O-2 gas during growth has made it possible to grow good epitaxial SrO films at...

Sharp interface structure of SrO film on hydrogen-terminated Si(100) is obtained by an alternate supply of Sr metal and O2 gas. The hydrogen-terminated Si is chemically inactive, especially against oxidation. The method of alternate supply of Sr and O2 gas makes it possible to cover Si surface with the first Sr layer for prevention of formation of...

Enhancement of the selectivity in organic molecular beam epitaxy was achieved by using pulsed molecular beams. It utilizes the nucleation kinetics before reaching stationary state of the growth. The time scale needed for the stationary state is estimated by changing the cycle time of the pulses.

The effect of chemical etching with a HCl/methanol solution on a polished sample of single-crystal YBa2Cu3Oy (001) was investigated by emission-angle-dependent X-ray photoemission spectroscopy (XPS). By chemical etching, the extrinsic Ba state in the surface region was removed without the effect of halogen. The bulk state of Y was also restored in...

The surface atomic and electronic structures of cuprous halide CuX (X=Cl, Br, and I) films, which were grown on various GaAs faces, have been studied by reflection high-energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectroscopy. Epitaxial growth in a layer by layer fashion was observed commonly on all GaAs faces...

Polarization dependence of transient absorption chane was investigated on a planary oriented vanadylphthalocyanine (VOPc) thin film grown heteroepitaxially on a KBr (001) surface by organic molecular beam epitaxy. Since the molecules were oriented planary on the surface and arranged with fourfold symmetry, two-dimensionality of the molecule, i.e. t...

Layered materials, represented by graphite, mica, MoS2 or GaSe, have a lamellar structure consisting of two-dimensional unit layers. Each unit layer is formed via strong covalent or ionic type bonds, while there is no strong bond between two unit layers; they are bound together via van der Waals-type weak interaction. Then layered materials can be...

We report photoemission spectra for the polycrystalline HgBa2CuO4+δ samples with various doping levels. As doping increases, we observed an increase in intensities around the Fermi level. The shift of leading edge about 10 me V was observed at 20K, but it persists well above T c ., indicating the existence of a normal state pseudogap

Single crystalline Ga2Se3 thin films were grown on GaAs(100) by molecular beam epitaxial (MBE) under Se-rich atmosphere. Reflection high-energy electron diffraction (RHEED) analysis suggests that the Ga2Se3 thin film is epitaxially grown on GaAs(100) with their 〈100〉 crystallographic directions aligned with each other. The electronic structure dete...

The growth of Mg has been examined on H-terminated Si (111) and the grown film was characterized by reflection high-energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectroscopy. Mg grows epitaxially on H–Si (111) in island form with an epitaxial orientation of Mg (0001) [112¯0]//Si (111)[11¯0]. At the very initial...

One of the major obstacles to realize various kinds of heterostructures is the lattice matching between constituent materials. This difficulty has been proved to be overcome if one uses the interface having van der Waals nature. This kind of interface can be formed when a layered material is grown on a cleaved face of another layered material. More...

The MoSe2/MoS2 system is investigated by scanning tunneling microscope (STM) and by its spectroscopic mode, scanning tunneling spectroscopy (STS). STM images show a hexagonal wagon-wheel-like pattern, which is made of bright lines and dark triangles. High-resolution STM images show that the bright line consists of twin lines separated by about 1 nm...

Ultrathin films of liquid crystal 12CB with monolayer-order thickness were grown on cleaved (001) surfaces of NaCl, KCl and KBr substrates by molecular beam deposition. The molecular arrangement and the morphology of the films were analyzed by high sensitivity reflection high energy electron diffraction and atomic force microscopy (AFM), respective...

Velocity distribution of the molecules emitted from effusion cells commonly used in molecular beam epitaxy was measured by using time-of-flight technique. The result for organic molecular phthalocyanine can be fitted by a shifted Maxwellian distribution. The effects of the temperature and the aspect ratios of the sources are discussed. © 1999 Ameri...

Selective epitaxial growth of organic materials is found and analyzed. It is observed during the molecular beam epitaxy of organic molecules and charge transfer complexes on ionic surfaces. The selectivity comes from lattice matching condition on critical nuclei formation in contrast to compound semiconductors for which covalent chemical bonding pl...

We propose a new method to fabricate nano-scale devices consisting of C 60 . C 60 molecules have a spherical shape with a diameter of 0.7 nm. It may be possible to consider each molecule as a quantum dot to fabricate a single-electron-tunneling de-vice which will work at room temperature. In order to control the position of a C 60 molecule on a dev...

Ultrathin films of vanadyl-naphthalocyanine (VONc) have been prepared on the (001) faces of RbI, KI, and KBr by molecular beam epitaxy. Molecular arrangements were determined by reflection high-energy electron diffraction. VONc molecules form square lattices ( square root 10* square root 10-R+or-18.4 degrees ) on these substrates. The lattices are...

A single-crystalline MgO film was grown on GaAs(001) by constructing a complex heterostructure with two alkali halide buffer layers. The growth temperature was decreased to 150°C as compared with direct growth of MgO on GaAs(001). Electron energy loss spectrum of the grown film agreed well with that of bulk MgO, indicating that surface stoichiome...

The growth of thick ZnSe films with high crystalline quality on a Si substrate is impaired by the 4.4% lattice mismatch at the interface. Based on the concept of van der Waals epitaxy, an InSe buffer layer was inserted between ZnSe and Si. The three-monolayer-thick buffer layer was grown by molecular beam epitaxy on a hydrogen-terminated Si(111) su...

Epitaxial growth of coronene ( C ₂₄ H ₁₂) was studied on substrates having no dangling bonds, such as hydrogen-terminated Si (111), MoS ₂, MoTe ₂, and muscovite by using reflection high-energy electron diffraction. It was found that the sticking coefficient and the maximum thickness of the epitaxi...

Ultrathin film growth of squaric acid (H2C4O4) has been attempted on (001) surfaces of various alkali halides. Epitaxial films were obtained on KCl, NaBr and KBr substrates. Ultraviolet optical absorption spectra of the films were strongly dependent on the substrates, suggesting a possibility of modifying correlated hydrogen bonding by `epitaxial p...

We report the molecular beam epitaxy (MBE) growth of the manganese(II) phthalocyanine thin films with unique crystal structure and the measurement of their magnetic properties. The epitaxial films were grown on hydrogen-terminated Si(111) substrates. Reflection high energy electron diffraction observations showed that the crystal structure of the f...

By molecular beam epitaxy, a thin (≈200 nm) ZnSe film was grown on a p-type Si substrate covered with an InSe buffer layer. The InSe buffer is used to bypass the huge lattice mismatch of 4.4% between ZnSe and Si in order to ensure the growth of a stress-free optically smooth ZnSe film. Reflection, photoluminescence and photocurrent properties at 30...

C60 molecules were deposited on a submonolayer InSe film which was grown on a MoS2 substrate. In the previous experiment on the growth of a C60 thin film on a GaSe/MoS2 heterostructure, C60 grew only on exposed MoS2 regions and never nucleated on GaSe domains at substrate temperature above 180°C. In the present case, however, C60 molecules grow onl...

The lattice mismatch at the heterostructure CdS/Si(111) is close to 8%. To relieve the structural stress at this interface, an InSe van der Waals-type buffer layer was grown between the Si substrate and the CdS film. After the Si(111) substrate surface was passivated by hydrogen, the InSe-buffer layer was grown on top by molecular beam epitaxy with...

Copper phtalocyanine (CuPc) films with the thickness controlled in molecular scales have been grown epitaxially on (0001) surfaces of layered materials, and electronic interaction at the interfaces have been studied by photoelectron spectroscopy. Materials with different electronic properties having different work functions (Evac) were chosen as th...

Electronic structure of a cadmium fluoride (CdF2) crystal was studied by low-energy electron-energy-loss spectroscopy. A new peak was observed in the valence excitation region, which may be ascribed to optically forbidden Γ′25 → Γ1 excitation. This result suggests that the Γ′25 state is located 1.5 eV below the Γ15 state.

The interaction between C60 molecules and a Si(111)7×7 surface has been investigated for various stages of C60 coverage by using high-resolution electron-energy-loss spectroscopy (HREELS). In the case of 0.2- and 0.6-ML films, their HREELS spectra indicate the formation of chemical bonds between C60 molecules and Si dangling bonds. After the comple...

Thermal desorption of epitaxial films of vanadyl phthalocyanine (VOPc:C32N8H16VO) and squaric acid (SQ:C4O4H2) was measured by using temperature programmed optical absorption spectroscopy. The activation energies for the desorption and pre-exponential factors were determined by measuring the amount of the molecules remaining in the film. Change in...

Electron energy-loss spectroscopy (EELS) has been applied to in situ prepared (DMe–DCNQI)2Cu (DMe–DCNQI=2,5-dimethyl-N,N-dicyanoquinonediimine). The intensity of the loss peaks changed significantly with the primary electron energies. It is probably due to the matrix element effects of the EELS. In conjunction with photoelectron spectroscopy using...

A novel method of fabricating organic material nanostructures using selective growth on patterned layered material surfaces has been developed. First, an epitaxial monolayer film of layered semiconductor GaSe was gown on a cleaved face of MoS2. Then, nanosize patterns were drawn by scratching only the grown GaSe film using an atomic force microscop...

Heteroepitaxial films of lamellar semiconductor GaSe were grown on MoS2 cleaved surfaces by molecular beam epitaxy, and its growth mechanism was investigated by atomic force microscope. At the initial stage of the growth, triangular islands of GaSe with a unit layer thickness are formed. There exist two types of domains, which have opposite orienta...

The surface roughness and stability of S or Se-terminated GaAs(111)B has been investigated by reflection high energy electron diffraction (RHEED), Auger electron spectroscopy (AES) and atomic force microscopy (AFM). RHEED streak patterns of S-terminated GaAs(111)B surfaces turned into spot patterns with increasing heating temperature. Se-terminated...

Ultraviolet photoelectron spectroscopy with various photon energies using synchrotron radiation was used to characterize chemical reactions associated with thin film growth of organic charge transfer complex (DMe-DCNQI)2Cu. Other molecular systems H2Pc, CuPc and C60 were also studied to clarify the origin of the systematic relation between the spec...

Ultrathin layered metal dihalide films (PbI2, CdI2) were grown on highly lattice mismatched (max. 44%) surfaces of several layered materials (LM's) and their growth features were studied by reflection high energy electron diffraction. Those metal dihalides grew epitaxially with their (0001) surfaces parallel to those of the substrates. They have th...