春山 雄一

We present a nanoimprint lithography (NIL) Si mold repair by Ga focussed ion beam (FIB). From the results, we conclude that a Si mold with projection and hollow defects can be repaired by Ga/sup +/ FIB. Ga appearance on a Si mold surface was clearly observed in NIL at over around 150 /spl deg/C.

We have studied the surface modification of synthetic organic polymers using the exposure of SR. Polymers such as polytetrafluoroethylene (PTFE), which is known as a hydrophobic material, and polyimide, which is known to have high heat resistance, are studied.

Three-dimensional nanostructures on a glass capillary have a number of useful applications such as manipulators and sensors in the various microstructures. This time, we have demonstrated the fabrication of a nozzle nanostructure on a glass capillary for a bio injector by 30 keV Ga+ focused-ion-beam assisted deposition with a precursor of phenanthrene vapor and etching. It has been demonstrated that nozzle nanostructures with various shapes and sizes have been successfully fabricated. An inner tip diameter of 30 nm on a glass capillary and a tip shape with an inclined angle have been realized.

Three-dimensional diamond-like carbon (DLC) mold fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD) using a precursor of phenanthrene has been applied to a nanoimprint process. Various 3D nanostructure DLC molds have been delineated by FIB-CVD using a computer-controlled pattern generator which is a commercially available pattern generator for electron beam lithography. Then, the molds were imprinted into hydrogen silsequioxane (HSQ) as a material replicated at room temperature. It was confirmed that the 3D mold, after nanoimprint lithography (NIL), kept its original shape, and 3D mold structures were successfully imprinted into HSQ. These results reveal that the 3D mold fabricated by FIB-CVD can be applied to NIL.

In the direct etching of spin-on-glass (SOG) films exposed using synchrotron radiation (SR) in the soft X-ray region at room temperature, etching depth increased with the SR dose. The etching rate of SOG films with organic content was much higher than that of SOG films without organic content. X-ray photoelectron spectroscopy (XPS) observation showed that the etching mechanism of SOG films without organic content was mainly SiO desorption and that of SOG films with organic content was mainly SiO and oxygen desorption. A 2 μm line and space etching pattern was transferred to SOG films with good fidelity by SR exposure.

We have studied the electronic structures in a wide temperature range for the Si(111) surface using photoemission spectroscopy combined with the laser annealing method. The temperature dependence of the Si 2p surface-sensitive core level photoemission spectra shows some gradual changes along with the thermal broadening above similar to1063 K. In addition, the spectral change in the valence band photoemission spectra was also observed across the 7 x 7-1 x 1 transition temperature. These results indicate that the surface band structure is changed along with structural change at the 7 x 7-1 x 1 transition temperature. With increase of the temperature, the shift of the Si 2p core-level photoemission spectra to the lower binding energy side was observed. We discuss the temperature-induced effects such as the thermal broadening and the observed shift.

The degrees of freedom in designing their shapes will be a great advantage in Focused-Ion-Beam Chemical-Vapor-Deposition (FIB-CVD), as we previously demonstrated with several three-dimensional nanostructures, i. e., wine glasses, coils, and pillars. Moreover, a very large Young's modulus were confirmed by observation of DLC pillar mechanical vibration. These characteristics are very useful for various biological devices. We will report fabrication of Nano Bio-Injector by using FIB-CVD.

We found that Spin-On-Glass (SOG) material acts as positive-type electron beam resist, and 200 nm line pattern was obtained using 100 nm beam diameter electron beam exposure and following buffered HF (BHF) development. Our previous report, (Jpn. J. Appl. Phys., vol.41, p.4304-4306, (2002)), direct etching of SOG by synchrotron radiation (SR) was confirmed, however, etching rate of polymethylmethacrylate (PMMA) was much higher than that of SOG. Therefore, SOG is the candidate material for high aspect ratio and fine pattern mask to organic materials such as PMMA by SR exposure. In this report etching of PMMA by SR using SOG mask was examined.

Nanoimprint lithography (NIL) is a very useful technique by which the fabrication of various nanostructure devices. A conventional mold is delineated by EB lithography and dry etching which has usually two-dimensional (2-D) patterns. 3-D structures are required in various devices such as optical devices (micro-lenses, photonic crystals, etc.). FIB-CVD is very useful to fabricate 3-D structures, as we previously demonstrated with several 3-D nanostructures. Moreover, a very large Young's modulus over 600 GPa were confirmed by observation of diamond-like carbon (DLC) pillar mechanical vibration. These characteristics are advantageous to make 3-D mold. In this paper, we will report 3-D NIL using DLC mold by FIB-CVD. We used a commercial available FIB system (SMI9200: Seiko Instruments Inc.) a 30-keV beam of Ga ions was focused on the substrate, which was in a precursor ambient. We used phenanthrene (C14H10) as the source gas for the amorphous DLC growth.

Fluorocarbon polymers are fluorishingly used as the material for industry from some characteristic advantages - chemical stability, thermal stability, excellent electric property and so on. One of other characteristics of fluorocarbon polymers was hydrophobicity of these surfaces, and fluorocarbon polymers were applicable to various industrial yields by taking advantage of this characteristic. However, in the several yields, such as painting and adhesion, this hydrophobicity has restricted the application of fluorocarbon polymers. In the present study, wettability on the surface of polytetrafluoroethylene (PTFE) chip was modified by exposure to synchrotron radiation (SR). This is the first report on SIR exposure effects about wettability of PTFE.

The resonant photoemission spectra and X-ray absorption spectra of temperature-induced valence transition material EuNi2(Si1-xGex)2 around Eu $3d$–$4f$, $4d$–$4f$ and Ni $2p$–$3d$ resonant excitation regions have been measured. From the comparison between the resonant photoemission spectra around the $3d$–$4f$ (bulk sensitive) and $4d$–$4f$ (surface sensitive) excitation regions, the Eu divalent component originating from the surface is separated from the bulk one. The divalent and the trivalent features of $4f$ electrons are obviously distinguished depending on the excitation conditions. It was confirmed that the intensity ratio of the $4f$ electronic structures between the Eu divalent and trivalent ions changes as a function of the temperature. The mean valence values estimated from the Eu $M$-edge X-ray absorption spectra and from the photoemission spectra were rather smaller than those obtained previously from the $L$-edge X-ray absorption spectra. The reason of the discrepancy is discussed. The spectral features and the resonant behaviors are well explained by a theoretical calculation based on the atomic model except for the strong contribution from the Ni $3d$ bands. In the resonant condition of the Eu divalent component, the spin flip satellite beside the $4f$ divalent states was observed. The photoemission spectra around the Ni $2p$–$3d$ excitation region show similar behavior to that of Ni pure metal.

The coordination of carbon atoms in diamond-like carbon (DLC) thin films formed by Ar gas cluster ion beam (GCIB) assisted deposition using fullerene as the carbon source was investigated by measuring near-edge X-ray absorption fine structure (NEXAFS) spectra of the carbon K-edge over the excitation energy range 275-320 eV, using synchrotron radiation. With attention to the peak corresponding to the transition of the excitation electron from a carbon 1s orbital to a π<FONT SIZE="-1">^*</FONT> orbital, relative sp<FONT SIZE="-1">²</FONT> contents of various DLC films were estimated. The sp<FONT SIZE="-1">²</FONT> contents of the DLC films formed by the GCIB-assisted deposition were observed to be lower than those of the DLC films formed by other methods. The hardness value measured with a nano-indentation technique was found to be strongly related to the sp<FONT SIZE="-1">²</FONT> content of the DLC film.

A strong thickness dependence of the correlation-induced satellite signal in Co 2p photoemission spectra is observed for Co films. It is found that the relative photoemission intensities around the satellite to the main peak increase when the Co film [on Cu(001)] thickness decreases. For example, for a 1-ML deposited film on Cu(001), the satellite is more intense than that for 3- or 5-ML Co on Cu(001). By using the oxygen surfactant effect, we were able to intentionally change the growth mode of 1-ML Co, and the 1-ML Co on O/Cu emerged as the most preferable one to map out the maximum satellite intensity. The results are explained from the viewpoint of dimension-dependent electronic structures of Co films, where the influences of the status of the d-band, d-d interaction, and the Cu4s-Co 3d hybridization together with the adatom (Co)- substrate (Cu) intermixing play vital roles in determining the satellite strength.

An in situ conduction measurement of metallic electronic states on the SrTiO3 (110) surface is reported. The electronic states were observed on the SrTiO3 (110) surface in our previous work after annealing in ultrahigh vacuum (UHV) at relatively low temperature. 800 degreesC, based on a sharp Fermi edge detected by ultraviolet photoemission spectroscopy and finite zero-bias differential conductance by scanning tunneling spectroscopy. The electric conductance measurement is performed in order to verify the metallic feature of the surface as a macroscopic property. For the measurement. a sample holder is designed which enables both annealing in UHV by electron beam and four-probe electric conduction measurement with uniform electric field. Conductance contributed by bulk is separated by measuring the decrease of total conductance by adsorption of oxygen at room temperature. which is supposed to modify only the surface electronic states. Surface conductance is deduced between 150 to 300 K and showed a metallic feature. Moreover, the surface conductance during exposure to oxygen is monitored in situ, and shows a reversible-like change depending on the oxygen pressure. This possibly evidences that the oxygen molecules which temporarily stay on the surface suppress the conduction by surface electrons. (C) 2001 American Vacuum Society.

Low energy electron diffraction, core level photoemission spectroscopy and magnetic dichroism have been applied to study Co films grown on oxygen-rich Cu(0 0 1) surfaces. The surface superstructure, electronic structure, chemical phase and magnetic stability in Co films were investigated. It was found that the initial oxygen was mostly segregated on top of the deposited Co films and promoted formation of a well-ordered c(2 x 2) phase. Besides, the correlation-induced satellite structure in Co2p photoemission spectra for a 1 ML (monolayer) Co film on O/Cu was found to be stronger than that for a 1 ML Co film on Cu. It is predicted that the growth conditions in both cases alter the Co d-d interaction and adatom (Co3d)-substrate (Cu4s) hybridization, and hence the observed satellite intensities. Additionally, a 5 ML film on oxygen-rich Cu(001) showed a magnetically stable phase at room temperature with in-plane magnetization. This is proof of an oxygen surfactant effect for Co epitaxial growth on Cu(001). (C) 2001 Elsevier Science B.V. All rights reserved.

For the development of new materials by SR technology, a new beamline was designed at the BL-7 of New SUBARU. This beamline consists of two branch lines, which are provided with an incident beam from a 3 m undulator by switching the first mirror. One of them is a high photon-flux beamline with a multilayered-mirror monochromator for the study of SR-process (BL7A) and another is a high-resolution beamline with a varied line spacing grating monochromator for the evaluation of nano-structure characteristics by SR-spectroscopy (BL7B). The useful range of emitted photons from 50 to 800 eV is covered at both beamlines. (C) 2001 Elsevier Science B.V. All rights reserved.

Combined systems for photoelectron spectroscopy using synchrotron radiation (SR) and laser have been constructed at BL5A and BL6A2 in the UVSOR facility, Okazaki. The systems consist of photoelectron spectrometers with high performance, mode-locked lasers, and timing electronic circuits. The laser pulses with repetition frequency of 90 MHz are synchronized with the SR pulses. An upgrade project to install a micro-ESCA at BL6A2, which is now in progress, is also reported

A straightforward method to deduce sample local density of states (LDOS) from the current-voltage characteristics (I-V) raw data in scanning tunneling spectroscopy (STS) is presented. The method is based on the relation between the I-V spectrum and the LDOS, both of which are treated as one-dimensional vectors: the I-V is generated from the LDOS by operating a triangular transfer matrix M. Then the LDOS is readily calculated from the I-V by operating the inverse matrix M-1, Which is also triangular. The method is an alternative for the conventional method to take (dl/dV)(VII), which often causes artificial peaks in LDOS at the onsets of I-V. Each row of M is determined by the tip density of states (DOS) and the barrier profile for the corresponding bias voltage. The tip DOS will be calculated from the I-V values measured at different tip-to-sample distances if the tip and sample have the same DOS and the barrier profile is symmetrical. As an example, the LDOS is calculated for the reduced SrTiO3 (110) on which the electronic states show metallic character depending on the annealing condition and sites. (C) 2001 Elsevier Science B.V. All rights reserved.

The electronic structures of organic salt DMTSA-BF4,, where DMTSA is 2,3-dimethyltetraseleno-anthracene, have been studied with photoelectron spectromicroscopy at various photon energies. The atomic orbital characters of the spectral features observed in the valence band region were determined from the photon energy dependence of the photoionization cross-section. The features between similar to1 and similar to4 eV are predominantly derived from both Se 4p and C 2p states. The features at similar to6 eV, between similar to7 and similar to 10 eV, and between similar to 10 and similar to 20 eV are predominantly derived from Se 4p, C 2p, and Se 4s and/or C 2s states, respectively The F 2p states originating from the counter anion BF, are located at similar to8 eV. By comparing the Se 3d core-level photoemission spectra between DMTSA-BF4 and DMTSA, it is suggested that DMTSA-BF4 has a mixed valence state. (C) 2001 Elsevier Science BN. All rights reserved.

Three-dimensional nanostructure fabrication has been demonstrated by 30 keV Ga+ focused ion beam assisted deposition using a aromatic hydrocarbon precursor. The characterization of deposited film on a silicon substrate was pet-formed by a transmission microscope and Raman spectra. This result indicates that the deposition film is a diamondlike amorphous carbon. Production of three-dimensional nanostructure is discussed. Microcoil, drill, and bellows with 0.1 mum dimension were fabricated as parts of the microsystem. Furthermore, microstructure plastic arts is advocated as a new field using microbeam technology, presenting one example of a microwine glass with 2.75 mum external diameter and 12 mum height. (C) 2000 American Vacuum Society. [S0734-211X(00)06806-2].

The origins of the anisotropic physical properties of CePtAs and LaPtAs were investigated by the optical conductivity and the XPS measurements. Optical conductivity spectra indicate that the property parallel to the c-axis is semiconducting and that perpendicular to the c-axis is metallic both for CePtAs and LaPtAs. The spectral features due to the pf mixing also show the anisotropic nature of CePtAs, namely, the intensity perpendicular to c-axis is stronger than that along c-axis. (C) 1999 Elsevier Science B.V. All rights reserved.

The magnetic linear dichroism (MLD) was used to study the magnetic properties of Ni-ultrathin film grown on ferromagnetic substrate Co(001). The MLD in photoemission has been measured for either the valence Ni3d states around the Ni3p threshold or 3p core level. Our dichroism measurements of the valence Ni3d states conclude that the resonance effect is present on MLD for `6 eV-satellite&#039; in the valence band photoemission whereas the main valence band peak shows nearly same MLD signal for the both on and off resonance. It is shown for the thinner film that the dichroism from Ni and Co3p core levels shows same sign with each other. This means that the Ni and Co are ferromagnetically coupled.

The electronic structures of organic salts (DI-DCNQI)(2)M with M = Cu and Ag, where DI-DCNQI is 2,5-diiodo-N,N'-dicyanoquinonediimine, were studied using photoelectron spectromicroscopy at various photon energies. From the photon energy dependence of the photoionization cross-section, the atomic orbital characters of the observed spectral features were determined. For both (DI-DCNQI)(2)Cu and (DI-DCNQI)(2)Ag, the C and N 2p states originating in the cyano group and the quinone ring are located at similar to 4.0 and similar to 6.5 eV, respectively. The Cu 3d states for (DI-DCNQI)2Cu and the Ag 4d states for (DI-DCNQI)(2)Ag are located at similar to 3.2 and similar to 5.2 eV, respectively. This indicates that the p pi-d hybridization at the Fermi level between the M ions and the N atoms of the DCNQI columns is larger for (DI-DCNQI)(2)Cu than for (DI-DCNQI)(2)Ag. The reason for the difference in the electronic structure between (DI-DCNQI)(2)Cu and (DMe-DCNQI)(2)Cu is also discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.

Photoelectron spectromicroscopy experiments have been started at the UVSOR facility of the Institute for Molecular Science. The commercial system (FISONS instruments, ESCALAB 220i-XL) has been connected to two beamlines which cover the photon energy range of 10 eV-5 keV. It is expected that spatial resolution of 2 μm for the imaging mode and 20 μm for the spectroscopic mode can be achieved. In conjunction with monochromatized (and polarized) synchrotron radiation light from the UVSOR storage ring, it is planned to undertake some experiments using this apparatus, not only for surface science but also for spectroscopy of small samples. As a demonstration of the apparatus, the magnetic domain image of Fe(110) surface with magnetic dichroism effect is shown. The photoemission spectra from small organic materials (DI-DCNQI)2-M (M = Ag, Cu) are also presented. © 1998 Elsevier Science B.V. All rights reserved.

The electronic structure of the reduced SrTiO3 (111) surface prepared by annealing, in ultrahigh vacuum has been studied using photoemission spectroscopy. In the photoemission spectrum of the reduced surface after annealing at 800 degrees C, a metallic state with a sharp Fermi cut-off is observed in the band gap region. For the reduced surface prepared by annealing at 1200 degrees C, on the other hand, the metallic state becomes drastically weak and a localized state centered at similar to 1.1 eV below the Fermi level is observed in the band gap region. Based on the low energy electron diffraction results, we will discuss the relationship between the spectral feature of these band gap states and the surface geometric structure. (C) 1998 Elsevier Science B.V.

The surface electronic structure of electron-doped SrTiO3 has been studied using the ultraviolet photoemission spectroscopy (UPS). By Nb substitution for Ti, two kinds of doping peaks are induced in the bulk band gap region of SrTiO3; a metallic peak with a sharp Fermi cut-off and a broad peak centered at similar to 1.3 eV below the Fermi level (E-F). The feature of these doping peaks is essentially identical to that recently reported in the case of the La substitution for Sr. The UPS spectra near E-F are shown to be very sensitive to the oxygen exposure. The behavior under the oxygen exposure can be explained by the formation of surface dipole layer by negative adsorbed species.

Quasiparticle spectra of the single-crystalline Ca1-xSrxVO3 which are the perovskite-type 3d(1) vanadium oxides are reported. The spectra have been measured around 14K by high-resolution ultraviolet photoemission spectroscopy. Systematic and prominent spectral weight redistribution due to a large electron correlation has been observed from a renormalized 3d band at the Fermi energy to higher binding energy incoherent features in going from SrVO3 to CaVO3.

The effect of doping electrons on the electronic structure of single-crystalline LaxSr1-xTiO3 samples (x = 0.001, 0.01, 0.05) has been studied for the fractured surface by photoemission spectroscopy. Two peaks in the band gap region of SrTiO3 (in-gap peaks) are induced by La substitution for Sr: a peak with a sharp Fermi cut-off(metallic peak) and a broad peak centered at similar to 1.5 eV below the Fermi level (similar to 1.5 eV peak). The spectral intensity of the metallic peak and the similar to 1.5 eV peak increase with the carrier concentration, but the spectral width of the metallic peak does not depend upon it. The behaviors of doping electrons on the electronic structure near the Fermi level of LaxSr1-xTiO3, such as no change in the spectral width of the metallic peak and the appearance of the similar to 1.5 eV peak, cannot be simply explained by the band theory. (C) 1997 Academic Press Limited.

Spectra from photoemission spectroscopy (PES) of a recently discovered layered-perovskite superconductor Sr2RuO4 are reported. The PES spectrum of Sr2RuO4 around the Fermi level (E-F) is apparently different from the non-interacting density of states obtained by a band calculation, suggesting the importance of strong electron correlation in this system.

Recently discovered layered-perovskite superconductor Sr2RuO4 shows significant spectral weight redistribution in its low energy photoemission spectrum. This suggests the existence of strong electron correlation in the system. Renormalized mass is estimated by the phenomenoiogical analysis of the spectrum. The importance of a momentum-dependent part of the self-energy is discussed.

The electronic structure of Sr1-xLaxTiO3 has been studied using the ultraviolet photoemission spectroscopy. Two kinds of doping states in the bulk band gap region of SrTiO3 are induced by La substitution for Sr; a metallic state with a sharp Fermi cut-off and a broad state centered at similar to 1.5eV below the Fermi energy. In proportion to the La concentration, the intensity of the metallic state increases. This behavior is simply explained by the band theory.

Angle-resolved photoemission spectra of SrTiO3 (100) and (110) surfaces have been obtained. The normal-emission data are analyzed using the direct transition model and, as a result, the valence band is determined along the Delta and Sigma lines in the bulk Brillouin zone. The empirical valence-band structure is found to be consistent with the band calculations if and only if proper magnitude of the O 2p crystal-field splitting is adopted. The effect of the O 2p crystal-field splitting on the band structure is discussed.

Quasiparticle spectra of the Ca1-xSrxVO3 and Sr2RuO4 single-crystals are reported. The spectra have been measured around 14K for Ca1-xSrxVO3 and 80K for Sr2RuO4 by high-resolution angle-integrated photoemission spectroscopy. Large spectral weight redistribution has been observed in both systems, suggesting an importance of the electron correlation.

Effect of doping electrons on the electronic structure of single-crystalline LaxSr1-xTiO3 samples (x=0.001, 0.01, 0.05) has been studied for the fractured surface by ultraviolet photoemission spectroscopy (UPS). Two peaks in the band gap region of SrTiO3 (in-gap peaks) are induced by La substitution for Sr; a peak with a sharp Fermi cut-off(metallic peak) and a broad peak centered at similar to 1.5 eV below E(F) (similar to 1.5 eV peak). The spectral intensity of the metallic peak and the similar to 1.5 eV peak increases with the carrier concentration, but the spectral width of the metallic peak does not depend upon it. The behaviors of doping electrons on the electronic structure near E(F) of LaxSr1-xTiO3, such as no change in the spectral width of the metallic peak and the appearance of the similar to 1.5 eV peak, can not be simply explained by the band theory.

The SrTiO3(110) surface, after annealing in ultrahigh vacuum (UHV) was observed by scanning tunneling microscopy/spectroscopy (STM/S). These observations were compared with the ultraviolet photoemission spectroscopy (UPS) and x-ray photoemission spectroscopy (XPS) data previously reported. The surface, after annealing at 800 °C, is dominated by flat regions where tunneling spectra are of metallic character, in agreement with the UPS data that showed a clear cutoff at the Fermi energy, EF. After annealing above 1000 °C, step edges along [11̄0] and rowlike structures along [001] with spacing approx.2.2 nm, close to 4√2a, are observed. The tunneling spectra showed an energy gap and an in-gap state approx.1 eV below EF, both of which are similar to those reported on the SrTiO3(100) surface after annealing in UHV. After 20 cycles of annealing above 1000 °C, a new ordering with c(2 × 6) periodicity is observed on the terraces. The STM/S results are explained by formation of (100) and (010) microfacets in the course of annealing in vacuum.

Microscopic structure and electronic states on the BaTiO3(100) single-crystal surfaces annealed in ultrahigh vacuum were observed by scanning tunneling microscopy and spectroscopy (STM/S). The surface step edges aligned preferentially along the [OOl] family of axes as the annealing temperature was increased. After annealing at temperatures above 800 °C, spatial ordering of Ti 3d-oxygen vacancy complexes appeared on the surface. The STS spectra showed in-gap electronic states at about 1.0 eV below Fermi energy, which agreed well with the results of ultraviolet photoelectron spectroscopy previously reported. © 1995 The Japan Society of Applied Physics.

The electronic structure of La2-xBaxCuO4 (x∼0.125) has beenstudied by ultraviolet photoemission spectroscopy. It is found that the LTO-&gt LTT phase transition has little effect on the electronic density of states (DOS) near the Fermi level. This suggests that the DOS change is not the main cause of the suppression of superconductivity, contrary to previous reports. We also make a comparison between La2-xBaxCuO4 (x≈0.125) and La2-xSrxCuO4 (x≈0.15) in the electronic DOS. © 1994.

We have performed angle-resolved photoemission and X-ray photoemission studies for stoichiometric and reduced SrTiO3(100) surfaces. In the empirical band structure of the O2p valence bands along the whole DELTA line in the bulk Brillouin zone, there is no essential difference between the stoichiometric and reduced surfaces. Our results are in excellent agreement with the calculation. In addition to the O2p valence band structure, two new states at approximately 1 eV and approximately 11 eV below Fermi level appear for the reduced surface (but not for the stoichiometric surface). We show that both of these states are closely connected with oxygen vacancies near the surface.