bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Bias Addition on the Gap-Filling Properties of Fluorinated Amorphous Carbon Thin Films Grown by Helicon Wave Plasma-Enhanced Chemical Vapor Deposition
Authors: Endo Kazuhiko , Matsubara Toru Tatsumi
Published: October 2002

Gap-filling properties of fluorinated amorphous carbon thin films ( a-C:F) for low-dielectric-constant interlayer dielectrics were investigated. The a-C:F films were grown by plasma-enhanced chemical vapor deposition from C4F8. It is demonstrated that by adding 400 kHz bias power to the substrate, the films could fill the gaps without leaving voids. Without bias application, the gap space was not filled. The bias power required to achieve complete gap filling was 30 W. The dielectric constant was 2.5 for the film with bias application.
Characterization of Pb(ZrxTi1-x)O3 Thin Film on Silicon Substrate with Heteroepitaxial Yttria-Stabilized Zirconia (YSZ) Buffer Layer
Authors: Horita Susumu , Tsuyoshi Kawada Tsuyoshi Kawada , Yukinari Abe Yukinari Abe
Published: October 2002

A c-axis highly oriented Pb(Zr

x

Ti1-
x

)O3 (PZT) film on Si(100) with a heteroepitaxial yttria-stabilized zirconia (YSZ) buffer layer was obtained by reactive magnetron sputtering. A 10-nm-thick YSZ buffer layer prevented the PZT film from reacting with the Si substrate at the substrate temperature of 650° C, leading to the production of a planar oriented PZT film. Polarization-voltage hysteresis measurements showed that the PZT/YSZ/Si structure had ferroelectric properties. Current-voltage and capacitance-voltage measurements indicated that this structure had crystalline defects which generated large absorption current with short relaxation time constants.
Study of Initial Stage of Molecular Adsorption on Si(100) by Scanning Tunneling Microscopy
Authors: Ken Nakajima Ken Nakajima , Tomihiro Hashizume Tomihiro Hashizume , Seiji Heike Seiji Heike , Satoshi Watanabe Satoshi Watanabe , Munehisa Mitsuya Munehisa Mitsuya , Takayuki Ikehara Takayuki Ikehara , Yasuo Wada Yasuo Wada , Toshio Nishi Toshio Nishi
Published: October 2002

We have investigated the initial stage of adsorption of a conjugated aromatic compound, 1,4-bis[β-pyridyl-(2)-vinyl]benzene (P2VB), on the clean Si(100)–2×1 surface. Using scanning tunneling microscopy (STM), we observed four different adsorption directions. An individual molecule appears as two or three bright spots, the brightness and distance between bright spots varying for different adsorption directions. We conclude that STM revealed the electronic states of the Si(100) dimers modulated by the adsorbed molecules, rather than the molecules themselves. Initial stage of adsorption of this molecule is explained by considering the molecular size and shape and strong interaction between the molecule and the Si dimers.
Size Control of Polydiacetylene Microcrystals
Authors: Katagi Hideyuki , Kasai Hitoshi , Okada Shuji , Oikawa Hidetoshi , Komatsu Kyoji , Matsuda Hiro , Liu Zhongfan , Nakanishi Hachiro
Published: October 2002

Aiming at the preparation of nanometer-size polydiacetylene microcrystals, the crystallization process during reprecipitation method was investigated using electron micrographs and light-scattering technique. We found that an amorphous nanoparticle was formed initially and subsequently crystallized. We conclude that amorphous nanoparticles must be sufficiently small in order to achieve nanometer-size crystals.
Fabricating Surface Enhanced Raman Scattering (SERS)-Active Substrates by Assembling Colloidal Au Nanoparticles with Self-Assembled Monolayers
Authors: Wang J. , Zhu T. , Tang M. , S. M. Cai S. M. Cai , Z. F. Liu Z. F. Liu
Published: October 2002

A simple method for fabricating SERS-active substrates with colloidal gold nanoparticles is reported. Spontaneous adsorption of HSCH2CH2NH2 on Au-evaporated glass led to a self-assembled monolayer with an amino-terminated surface, on which mono-dispersed colloidal Au nanoparticles were assembled into a two-dimensional array. Thus-prepared substrates were shown to be SERS-active, evidenced by the enhanced Raman scattering from BPE and an azobenzene derivative. The SERS enhancement factor was calculated to be 3×103. Raman mapping and AFM imaging disclosed the good uniformity of the particle distribution on the surface on micrometer scale.
Logic Operation Using a High Tc Coupled Superconducting Quantum Interference Device
Authors: Saitoh Kazuo , Fuke Hiroyuki , Tadashi Utagawa Tadashi Utagawa , Youichi Enomoto Youichi Enomoto
Published: October 2002

Operation principle of AND/OR logic has been realized in a coupled high-T
c Superconducting QUantum Interference Device (SQUID). The device consists of rf- and dc-SQUID's. The logic operation is based on the nonlinear characteristics of the internal and external magnetic flux in the rf-SQUID. Results of the logic operation can be read out by the dc-SQUID. The device is made of NdBa2Cu3O7-δ superconducting thin film with superconducting weak links fabricated using a narrow-focused Ga-ion beam technology.
Ablation of Fused Quartz by Ultraviolet, Visible or Infrared Laser Coupled with VUV Laser
Authors: Zhang Jie , Sugioka Koji , Wada Satoshi , Hideo Tashiro Hideo Tashiro , Koichi Toyoda Koichi Toyoda
Published: October 2002

Ablation of fused quartz by a 266, 532 or 1064 nm wavelength laser coupled with VUV laser (133–184 nm) was reported. With the VUV-266 nm laser system, high-quality ablation of fused quartz with a well-defined patterned structure and a surface roughness value as small as 46.2 nm at the circumference of the patterned structure was carried out. The ablation quality was poorer and the surface roughness value was higher, at 97.8 nm, when the VUV-532 nm laser system was used, but the ablation quality was still better than in the case of 266 or 532 nm single wavelength ablation. In contrast, clean ablation of fused quartz could not be achieved using the VUV-1064 nm laser system. The ablated region appeared to be an undefined crater-like structure, and the surface roughness value reached 121.0 nm, which were almost the same characteristics as in the case of 1064 nm single wavelength ablation. On the basis of the band structure of the fused quartz and the excited-state absorption determined through coupling of the VUV laser and the ablation laser (266, 532 or 1064 nm), the ablation mechanism was discussed.
Organic Photovoltaic Cell with Donor-Acceptor Double Heterojunctions
Authors: Akihiko Fujii Akihiko Fujii , Anvar A. Zakhidov Anvar A. Zakhidov , Victor V. Borovkov Victor V. Borovkov , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

An organic photocell, which has a multilayer structure consisting of poly(2,5-dioctyloxy-p-phenylenvinylene) (OOPPV)/octaethylporphine (OEP)/backminsterfullerene (C60), has been fabricated. The photocurrent yield spectra are measured in terms of the light absorption in the OEP layer, the exciton migration and the charge generation at both organic heterojunctions. That is, the double heterojunctions OOPPV/OEP and OEP/C60 contribute to the charge generation by excitonic dissociation. The mechanisms of charge generation and photocurrent enhancement are discussed taking the energy band structure and photoinduced charge transfer into consideration.
100-K Operation of Al-Based Single-Electron Transistors
Authors: Yasunobu Nakamura Yasunobu Nakamura , ChiiDong Chen ChiiDong Chen , Jaw-Shen Tsai Jaw-Shen Tsai
Published: October 2002

We have made Al-based single-electron transistors with an artificially fabricated 20-nm island electrode by utilizing standard electron-beam lithography and three-angle shadow evaporation. A periodic gate-voltage dependence of current at above 100 K is demonstrated with this device. In addition, we increased the charging energy about 20% by using anodization.
Phase Variation of Amorphous-Si and Poly-Si Thin Films with Excimer Laser Irradiation
Authors: Kitahara Kuninori , Suga Katsuyuki , Akito Hara Akito Hara , Kazuo Nakajima Kazuo Nakajima
Published: October 2002

Excimer laser induced crystallization of Si thin films was studied by Raman spectroscopy and transmission electron microscopy. Single pulses of laser with various energies were irradiated on two types of starting materials to analyze complicated effects of the laser crystallization. For energies higher than a threshold value, an obvious difference in crystallization was found between starting materials of amorphous Si (a-Si) and laser-crystallized Si (lc-Si). Microcrystals were generated in the former but not in the latter, which is attributed to the presence of nuclei which remained deep within the lc-Si film during the film melting. Phase variation of a-Si and degradation of lc-Si induced by small-energy irradiation were also demonstrated.
Influence of Crystal Originated Particles on Gate Oxide Breakdown
Authors: Deai Hiroyuki , Iwasaki Toshio , Ikematsu Yoichi , Kawakami Kazuto , Harada Hirofumi , Atsuki Matsumura Atsuki Matsumura
Published: October 2002

Defects causing gate oxide breakdown in Czochralski silicon were evaluated using a location marking technique by copper plating. The cross sectional structure of the defect was observed by a combination technique of focused ion beam (FIB) etching at the marked location and transmission electron microscopy (TEM) and found to have similar appearances and sizes to those of crystal originated particles (COPs) observed by atomic force microscopy (AFM). Correlation between locations of the defects at a wafer surface determined using the copper plating and those of COPs determined using a particle counter was investigated for various electric field applied for the copper plating. We found that COPs are one of the major factors causing gate oxide breakdown at fields around 4 MV/cm, while other factors become dominant when a higher electric field is applied.
(2 × 6) Surface Reconstruction of GaAs (001) Obtained by Hydrogen Sulfide Irradiation
Authors: Jun Suda Jun Suda , Yoichi Kawakami Yoichi Kawakami , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: October 2002

Sulfur treatment of GaAs (001) using hydrogen sulfide to obtain a (2×6) S-terminated surface is presented. When a GaAs substrate with no epitaxial buffer layer is annealed at up to 580°C in a high vacuum (< 1 ×10-9 Torr), a mixture of (3×6) and (4×6) Ga-terminated reconstructions is observed. After cooling of the substrate to 300°C and irradiating it with hydrogen sulfide, a clear (2×6) S-terminated surface reconstruction appears in a few minutes.
Plasma Polymerization for the Deposition of an Electroluminescent Polymer Layer
Authors: Sun Runguang , Peng Junbiao , Kobayashi Takayoshi , Ma Yuguang , Zhang Haifeng , Liu Shiyong
Published: October 2002

Radio frequency plasma polymerization is introduced to fabricate an emissive polymer layer as an organic electroluminescence (EL) device. Utilizing this technique, a thin polymer film is deposited directly onto a substrate from a starting monomer, and the thin polymer film obtained was found to be uniform and smooth. By employing a cell of ITO(indium-tin oxide coated glass)/plasma polymerized naphthalene/Al configuration, a stable and uniform blue-green (centers at 485 nm) EL is observed over 6 V DC bias. The external quantum efficiency of this device is estimated to be about 0.01%, which is comparable with those of the single-layer polymer EL cells in which the emitting polymers are synthesized by chemical polymerization.
P-Type Doping of the Group V Elements in CuInS2
Authors: Yamamoto Tetsuya , Katayama-Yoshida Hiroshi
Published: October 2002

We have studied the electronic structures ofp-type doped CuIn(S0.9375V0.0625)2(V=N, P, As, Sb or Bi) based onab-initioelectronic band structure calculations using the augmented spherical wave (ASW) method. We determined that P and Sb atoms are extremely suitable dopants which can be substituted for S atoms inp-type doped CuInS2crystals with lower resistivity. On the other hand,p-type CuInS2crystals doped with N or Bi had a higher resistivity than those doped with P or Sb.
Low Contact-Resistance and Shallow Pd/Ge Ohmic Contacts to n-In 0.53Ga 0.47As on InP Substrate Formed by Rapid Thermal Annealing
Authors: Yeh Yung-Hui , Jiun-Tsuen Lai Jiun-Tsuen Lai , Joseph Ya-min Lee Joseph Ya-min Lee
Published: October 2002

Shallow Pd/Ge ohmic contacts to n-type In0.53Ga0.47As with low specific contact resistivity are obtained by the rapid thermal annealing method. For samples annealed at 425°C for 30 s, the lowest resistivity value is 6.66×10-8 Ω·cm2 and the average value is 1.4×10-6 Ω·cm2. For samples annealed at 425°C for 60 s, the lowest resistivity value is 2.13×10-7 Ω·cm2 and the average value is 8.6×10-7 Ω·cm2. Secondary ion mass spectrometry (SIMS) analysis shows that the ohmic contact is very shallow. It is found that there is a correlation between gallium and indium SIMS signal bumps and good ohmic contact behavior.
Adsorption Site Determination by Reflection High-Energy Electron Diffraction Combined with Interface Energy Calculation
Authors: Kamei Masayuki , Yasuaki Tanaka Yasuaki Tanaka , Yoshihiko Gotoh Yoshihiko Gotoh
Published: October 2002

A new method of reflection high-energy electron diffraction combined with interface energy calculation (RHEED-IEC) was proposed for the purpose of determining adsorption sites on substrate surfaces. This RHEED-IEC was adopted to determine the adsorption sites in a model of the \sscriptsize(  4 \atop-13 \atop3) superstructure of Ce film grown on a Mo(110) surface. The adsorption sites in this Ce \sscriptsize(  4 \atop-13 \atop3) superstructure were determined not to be the hollow sites where a single Ce atom is expected to adsorb, but the highly symmetric bridge sites of the Mo(110) surface.
Observation of the Formation Processes of Hollow Voids at the Interface between SiC Film and Si Substrate
Authors: Nobuo SONODA Nobuo SONODA , Yoshihiko WATARI Yoshihiko WATARI , Yong SUN Yong SUN , Tatsuro MIYASATO Tatsuro MIYASATO
Published: October 2002

The formation processes of hollow voids which appear at the interface of cubic SiC film/Si substrate are observed using scanning and transmission electron microscopy. The cubic SiC films are prepared on a (100) Si substrate which is kept at a temperature ranging from 700°C to 1000°C by means of reactive hydrogen plasma sputtering of a ceramic SiC target. We found that the hollow voids are first formed at lattice defects near the Si substrate surface due to the high reactivity of the defects, and are later formed at reaction zones which form by the film growth nuclei with the Si substrate surface. Formation and growth of the hollow voids are complex processes that depend on conditions such as substrate temperature, areal density of both the lattice defects and the film growth nuclei at the Si substrate surface, and diffusion rate of gas atoms through the growing film.
SrTiO 3 Capacitor with Relative Dielectric Constant of 200 on GaAs Substrate at Microwave Frequency
Authors: Nishimura Takeshi B , Iwata Naotaka , Takemura Koichi , Kuzuhara Masaaki , Miyasaka Yoichi
Published: October 2002

An RF-sputtered SrTiO3 (STO) capacitor was fabricated on a GaAs substrate. Microwave characterization exhibited a relative dielectric constant (ε

r
) of 200 up to 20 GHz. This high ε
r was obtained when the base electrode and the STO film were sputter-deposited in succession. A novel Pt/Ti/Pt/Ti base metal exhibited high tolerance against ion-milling, resulting in lower Ohmic resistance compared to the conventional base metal, Pt/Ti.
Stabilization Mechanism of Liquid-Lithium Cones during Field Electron Emission
Authors: Hata Koichi , Nakayama Fujio , Yahachi Saito Yahachi Saito , Akinori Ohshita Akinori Ohshita
Published: October 2002

For a liquid-lithium coated W<111> field emitter tip, the mechanism of stabilization of the liquid cone during electron emission was investigated by the use of a probe-hole type field emission microscope. A single liquid-lithium cone was formed on the optical axis using a (111)-remolded tip and the emission current from the single cone was measured. An oscilloscope trace of the emission current passing through a small probe hole indicated a stable direct current with a fluctuation of less than 0.1%. The probe current obeyed the Child-Langmuir law approximately, and therefore it is reasonable to consider that the liquid-lithium cone is stabilized by the space charge. The angular intensity reached about 30 mA/sr at a total emission current of 300 µA.
Sheath Potential in the Accelerating Region of an Electron-Beam-Excited Plasma Apparatus
Authors: Miyano Ryuichi , Izumi Shinya , Kitada Ryouji , Fujii Motoyuki , Ito Shunjiro Ikezawa
Published: October 2002

Recently, the decrease of sheath potential using a magnetic field has been used for the improvement of various apparatuses. With this in mind, the measured sheath potentials are quantitatively compared with the theoretical current balance equations at the sheath edge in the accelerating region using an electron-beam-excited plasma (EBEP) apparatus, where a strong beam exists. As a result, it is found that the radial profile of sheath potential depends on the beam potential (E
b
′) at the sheath edge in the plasma, and the axial profile on the beam potential (E
b) and electron-beam temperature (T
b).
Detection of Synchrotron Radiation by Nb-Based Superconducting Tunnel Junctions
Authors: Shimizu Keisuke Maehata , Masami Yoshizawa Masami Yoshizawa , Masaki Katagiri Masaki Katagiri
Published: October 2002

X-rays extracted from synchrotron radiation were detected by Nb-based superconducting tunnel junctions. Measurements were carried out under severe noisy circumstances. Spectra of X-rays were obtained for energies in a range of 4 to 15 keV. The energy for single electron collection increased by 20% at X-ray energies from 4 to 15 keV.
Coercivity Enhancement in Co–Pt Alloy Films due to Annealing in Air
Authors: Shiomi Shigeru , Nakakita Tomoki , Tanaka Rika , Tadashi Kobayashi Tadashi Kobayashi , Morio Masuda Morio Masuda
Published: October 2002

Co–Pt alloy films with out-of-plane magnetization were annealed both in air and in vacuum. Annealing in air resulted in a significant increase in coercivity H
c, while annealing in vacuum hardly increased H
c. Irrespective of Co–Pt alloy layer thickness, the most significant increase in H
c was induced when saturation magnetic moment m
s was reduced to 0.5–0.7 of that before annealing. The dependence of H
c and hysteresis loss on magnetic field direction suggests that the enhancement in H
c results from the division of Co–Pt alloy layer into single-domain particles by the oxidation of Co atoms at grain boundaries.
Preparation of Ti–Al–N Electrode Films by Pulsed Laser Ablation for Lead-Zirconate-Titanate Film Capacitors
Authors: Morimoto Akiharu , Yasuhiro Yamanaka Yasuhiro Yamanaka , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

Titanium-aluminum-nitride (Ti–Al–N; TAN) electrode films were prepared by pulsed laser ablation on (100)Si and (100)MgO substrates for ferroelectric lead-zirconate-titanate ( Pb(Zr0.52Ti0.48)O3; PZT) thin-film capacitors. Capacitors with rather randomly oriented PZT films on the TAN/(100)Si did not show a ferroelectric hysteresis loop, but the capacitor with preferentially [100]-oriented PZT film on the TAN/(100)MgO did. This suggests that a TAN-electrode film was grown on (100)MgO with a high oxidation resistance at the high temperature employed for ferroelectric oxide preparation.
Transport Property of (La1-xAx)MnO3 (A=Ca, Sr, Ba)
Authors: Tsutom Yotsuya Tsutom Yotsuya
Published: October 2002

The transport properties of the (La1-
x

A

x

)MnO3 (A=Ca, Ba, Sr) system were investigated. The samples were prepared by a solid reaction route and were polycrystalline in nature. After sintering at 1420° C for 24 h, they were cut into rectangular sheets for resistance measurement. At first, the resistance of the (La1-
x

A

x

)MnO3 increased with decreasing temperature, and after reaching a maximum, decreased rapidly. The resistance maximum is probably related to the first-order phase transition, since it showed a hysteresis behavior. A ferromagnetic transition was also recognized. The Curie temperature was higher than that of the resistance maximum. Below the Curie temperature, a giant magnetoresistance (GMR) was observed for La0.7Ca0.3MnO3 and La0.7Ca0.2Sr0.1MnO3. However, La0.7Ca0.2Ba0.1MnO3, which had the same crystal structure, ferromagnetic transition and metallic behavior as La0.7Ca0.2Sr0.1MnO3, did not show GMR. This suggests that not only the spin ordering of the Mn site but also the Jahn-Teller effect may play an important role in the GMR.
Mechanism of Stoichiometric Deposition of Volatile Elements in Multimetal-Oxide Films Prepared by Pulsed Laser Ablation
Authors: Masuda Atsushi , Matsuda Kazuko , Yonezawa Yasuto , Akiharu Morimoto Akiharu Morimoto , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

The mechanism of stoichiometric deposition of volatile elements such as Pb and Bi, which have high vapor pressures, is studied for lead zirconate titanate (PZT) films and bismuth iron garnet (BIG) films, respectively, both prepared by pulsed laser ablation in various ambients and at various temperatures. It is found that O2 ambient plays a crucial role for the stoichiometric deposition of volatile elements at elevated deposition temperatures. O2 ambient at a low pressure brings about deficiency of volatile elements. On the other hand, if O2 ambient at a high pressure is employed, the composition of volatile elements is preserved because the oxide of the volatile element covers the growing surface. Pb deficiency is observed even for films deposited at room temperature in a vacuum ambient. This phenomenon is considered to originate from the vaporization of Pb during the flight process. Therefore O2 ambient with a moderately high pressure is important for stoichiometric deposition. O2 ambient with excessively high pressure, however, solidifies droplets and brings about severer thickness distribution and/or a rougher surface than those formed at a moderately high pressure.
Thin-Film Slot Antennas for 2.5 THz Submillimeter Radiation
Authors: Shimizu Takashi , Abe Yasuhiko , Gamo Yoshizumi Yasuoka
Published: October 2002

Thin-film slot antennas for 2.5 THz submillimeter radiation were fabricated by the photolithographic method on a fused quartz substrate. The antenna properties were investigated by measuring the antenna patterns for 2.5 THz CH3OH laser radiation. It was found that the fabricated antennas work as receiving antennas at 2.5 THz. The measured antenna patterns agreed with the theoretical antenna patterns in free space despite the dielectric substrate.
Intermetal Dielectric Gap Fill by Plasma Enhanced Chemical Vapor Deposited Fluorine-Doped Silicon Dioxide Films
Authors: Woo Sik Yoo Woo Sik Yoo , Richard Swope Richard Swope
Published: October 2002

Fluorine-doped tetra-ethoxy-ortho-silicate (F-TEOS) silicon dioxide films were deposited using a dual frequency multi-station sequential plasma enhanced chemical vapor deposition (PECVD) system. F-TEOS films with various Si–F content were deposited using mixture of vaporized TEOS, O2 and C2F6. The Si–F content and gap filling capability of F-TEOS films was investigated under various deposition conditions. The gap filling capability was found to be dependent upon wafer temperature, pressure and gas phase reactant concentrations, but is predominantly dependent on Si–F content. Aspect ratios (AR: height of metal lines versus spacing between metal lines) up to 1.35:1 with 0.25 µm spacing were filled with no observable seams and voids.
YBa2Cu3Ox Crossover Structures Using CeO2 Film as Insulating Layer
Authors: Sato Hiroshi , Miyakawa Ryuji , Nakamura Norito , Gj\oen Stein R. , Hiroshi Akoh Hiroshi Akoh , Susumu Takada Susumu Takada
Published: October 2002

We have fabricated YBa2Cu3O

x

(YBaCuO) crossover structures using CeO2 films as insulating layers, varying the area from 10×50 to 50×50 µm2. The fabrication process of the crossover structure was performed ex situ, by combining the deposition of YBaCuO and CeO2 films with the microfabrication of YBaCuO bridges and contact holes in the CeO2 layer using a liquid-nitrogen-cooled dry etching method. Even though we used ex situ processes, the bottom YBaCuO bridges had a transition temperature T
c of 87 K and a critical current density J
c of 1.0×105 A/cm2 at 77 K. Typical crossover resistivity was more than 2.0×108 Ω·cm below 80 K even for 50×50 µm2 structures. This indicates that CeO2 is a promising material for insulating layers in high-T
c superconducting devices.
Ion and Neutral Temperatures in a Novel Ultrahigh-Frequency Discharge Plasma
Authors: Toshiki Nakano Toshiki Nakano , Hiroto Ohtake Hiroto Ohtake , Seiji Samukawa Seiji Samukawa
Published: October 2002

Ion and neutral temperatures are measured in an ultrahigh-frequency discharge plasma through Ar and Ne by Doppler-shifted laser-induced fluorescence. The ion and neutral temperatures are estimated to be ≈0.066 eV (770 K) for Ar+ and 0.033±0.004 eV ( 380 ±50 K) for Ne, respectively. These temperatures are lower than those reported for electron cyclotron resonance and helicon wave plasmas. The low temperatures are attributed to the low electron temperature ( ≈2 eV) and excellent uniformity of the UHF plasma.
Experimental Study of Beam Steering in 980-nm InGaP Cladding Lasers
Authors: Ohkubo Michio , Ikegami Yoshikazu , Tetsurou Ijichi Tetsurou Ijichi , Takao Ninomiya Takao Ninomiya
Published: October 2002

The beam steering phenomenon was directly observed by means of backplane electroluminescence in 980 nm InGaP cladding power lasers. The electroluminescence of the lasers which showed lateral beam steering had a periodic pattern along the active region, which was assumed to be due to spatial hole burning. The period of this pattern was roughly estimated using the effective refractive index method. A laser satisfying the cut-off condition for higher lateral modes did not exhibit a periodic pattern of electroluminescence.
Reflection High Energy Electron Diffraction Intensity Oscillations during the Growth of ZnSe on Cleaved GaAs(110) Surface by Molecular Beam Epitaxy
Authors: Ko Hyun-Chul , Yamaguchi Shigeo , Kurusu Hitoshi , Kawakami Yoichi , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: October 2002

Up to 30 periods of the intensity oscillations of reflection high energy electron diffraction (RHEED) during the growth of ZnSe on GaAs(110) by molecular beam epitaxy (MBE) were observed for the first time. The GaAs(110) surface was obtained by cleaving a GaAs(100) wafer in ultra high vacuum (UHV). The oscillation behavior was strongly dependent on the partial beam pressure ratio p(Se)/ p(Zn). Stable oscillations were obtained at a p(Se)/ p(Zn) of 1.0 and a growth temperature of 250° C. The optimum growth conditions were different from those for ZnSe growth on a GaAs(100) surface. From double crystal X-ray diffraction measurements, epitaxial growth was confirmed to be pseudomorphic.
Vapor Phase Epitaxial Growth of ZnTe Films Using Metallic Sources
Authors: Tetsuo Muranoi Tetsuo Muranoi , Masami Sekine Masami Sekine
Published: October 2002

Undoped ZnTe films with very low resisitivity were grown by vapor phase epitaxy (VPE) with elemental Zn and Te as source materials. The source vapors were transported separately to the vicinity of the substrates, kept at 450–560\degrC, by flow through a thin quartz tube. The growth rate showed two activation energies (45 kcal/mol and 15 kcal/mol) according to the growth temperature. The epitaxial growth was confirmed by using high energy electorn diffraction (RHEED) measurements. Hall effect measurements showed p-type conductivity. Conductive films were obtained when the flow rates of Zn and Te were almost equal and the substrate temperature was above 500°C.
Antimony Co-Implantation to Suppress Boron-Penetration in P+-Poly Gate Metal-Oxide-Semiconductor Transistors
Authors: Sun Wein-Town , Yang Ching-Song , Liaw Ming-Chi , Charles Ching-Hsiang Hsu Charles Ching-Hsiang Hsu
Published: October 2002

A novel method for suppressing boron-penetration is reported. Antimony co-implantation with BF2 in p-poly gate of metal-oxide-semiconductor (MOS) device is found to effectively alleviate the boron-penetration enhanced by the existence of fluorine. The boron-penetration in BF2 implanted poly-gate is observed to be significantly reduced as the dose of co-implanted antimony increases. From Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis, the suppression of boron-penetration is shown to be possibly due to the formation of Sb-F compound, which reduces the fluorine enhanced boron diffusion.
Temporal Mössbauer Absorber Thickness Effect Demonstrated Using Synchrotron Radiation
Authors: Xiaowei Zhang , Yoda Yoshitaka , Seto Makoto , Sugiyama Hiroshi , Kikuta Masami Ando
Published: October 2002

It is well known in Mössbauer spectroscopy that the nuclear resonance-absorption linewidth is dependent upon the absorber thickness. This phenomenon was demonstrated in the time domain using synchrotron radiation pulses and a single-absorption-line 57Fe-enriched specimen. The measured time spectra give the simplest time response of nuclear resonant forward scattering for the excitation pulse.
Transport Properties of Two Quantum Dots Connected in Series Formed in Silicon Inversion Layers
Authors: Hideyuki Matsuoka Hideyuki Matsuoka , Haroon Ahmed Haroon Ahmed
Published: October 2002

We have studied the transport properties over a range of temperatures of two quantum dots connected in series formed in silicon inversion layers. The inter-dot interaction as well as the electron number can be changed by means of the field effect in our device. For weak inter-dot interactions, the device shows a periodic current oscillation and a biquadratic temperature-dependent current due to co-tunneling. On increasing the inter-dot interaction, we have observed splitting of peaks and estimated the typical inter-dot capacitance to be 1.3×10-18 F.
Laser Ablation of Alkaline Earth Metals Investigated by Time-of-Flight Mass Spectroscopy: Ion Desorption by Core-Electron Excitation
Authors: Nishikawa Hiroaki , Masaki Kanai Masaki Kanai , Tomoji Kawai Tomoji Kawai
Published: October 2002

The time-of-flight distribution and the amount of desorbed monovalent ions have been measured in the laser ablation of alkaline earth metals. The obtained relationship between the amount of ions and the laser fluence indicates that the desorption is caused by 5-, 4- and 3-photon processes for Ca, Sr and Ba, respectively when an ArF excimer laser is used as a light source. On the basis of the results, a model is proposed in which the laser ablation of the alkaline earth metals is triggered by excitation of the core electrons at the highest energy level.
Molecular Beam Epitaxy of ZnSe Films and ZnCdSe/ZnSe Quantum Wells on Cleavage-Induced (110) Surfaces
Authors: Zhang Baoping , Yasuda Takashi , Takanari Yasui Takanari Yasui , Yusaburo Segawa Yusaburo Segawa
Published: October 2002

ZnSe films and ZnCdSe/ZnSe quantum wells were grown for the first time on cleavage-induced GaAs(110) and ZnSe(110) surfaces. When the deposition began, the overgrown surface of the ZnSe film became flat within a few seconds. The optical properties of the ZnSe(110) films and ZnCdSe/ZnSe(110) quantum wells were comparable to those grown on GaAs(001) substrates, indicating the high-quality of these materials. Using a two-step MBE method, high-quality epitaxial materials were grown on a cleavage-induced ZnSe(110) surface. This work demonstrates the possibility of fabricating high-quality quantum wires on a (110) surface obtained by cleaving ZnCdSe/ZnSe(001) superlattices.
Effect of Morphology on Photovoltaic Properties of Titanyl Phthalocyanine
Authors: Tsuzuki Toshimitsu , Kuwabara Yoshiyuki , Noma Naoki , Willis Yasuhiko Shirota
Published: October 2002

The effect of morphology on the photovoltaic properties of titanyl phthalocyanine (TiOPc) has been studied. pn-Heterojunction devices consisting of TiOPc with different morphologies and N,N'-dimethyl-3,4:9,10-perylenebis(dicarboximide) (MPCI) sandwiched between indium tin oxide (ITO) and Au electrodes were fabricated. Cells fabricated using crystalline α-TiOPc film as the p-type semiconductor exhibit much higher conversion efficiency upon irradiation with light which is mainly absorbed by TiOPc than devices fabricated using amorphous TiOPc film.
Observation of Si(001) Surface Domains in Absorption Current Images of an Electron Microscope
Authors: Doi Takahisa , Ichikawa Masakazu , Shigeyuki Hosoki Shigeyuki Hosoki
Published: October 2002

We investigated a Si(001) surface by scanning electron microscopy when an electron beam was incident at grazing angles on it. The absorption current images were taken using the signal of the absorbed current in a sample. The 2×1 domains and the 1×2 domains were distinguished in the absorption current images, and the contrast of the domains was reversed by changing the incident conditions. The 2×1 domain has a 2×1 dimer perpendicular to the incident beam and the 1×2 dimer is perpendicular to the 2×1 dimer. The contrast in the absorption current images was due to the anisotropical properties of the dimer on the Si(001) surface; the surface potential or the cross section of the released electrons.
Redox Potential Imaging Sensor
Authors: Noriko Oba Noriko Oba , Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

We developed a chemical imaging sensor which can be used to visualize the spatial distribution and temporal evolution of redox potential in chemical reaction systems. It is based on the light-addressable potentiometric sensor (LAPS), in which the insulating surface is found to be sensitive not only to the pH value but also to the redox potential of the adjacent electrolyte: a voltage shift of 50.3 mV/decade was observed for the [K3Fe(CN)6]/[K4Fe(CN)6] system. We show that it is possible to measure the distribution of redox potential with high speed (22 s for 64×64 pixels) using this sensor.
Stability of Si(111)√ 3×√ 3R30°-B Surface in Air
Authors: Mori Ryosuke , Kumagai Yoshinao , Tanaka Masaya , Masaki Yamamoto Masaki Yamamoto , Fumio Hasegawa Fumio Hasegawa
Published: October 2002

The Si(111)√ 3×√ 3R30°–B surface was prepared by irradiation of HBO2 in a molecular beam epitaxy (MBE) system, and its stability in air was studied using reflection high-energy electron diffraction (RHEED) and contact angle measurements. The boron (B)-passivated Si(111) surface was found to be much more stable against oxidation than a clean Si(111)7×7 surface. The measurements of contact angle between the surface and a water droplet revealed that the B-passivated Si(111) surface was hydrophilic (∼5°), and that the contact angle increased with oxidation of the surface and saturated at 27°. It was also found that the contact angle of the Si(111) native oxide increases from ∼0 to ∼27° in about 1000 minutes in room air or nitrogen ambient.
Tunneling Study of the Valence Band Structure of Pb 1-xEuxTe
Authors: Takafumi Syoji Takafumi Syoji , Yoichi Miyahara Yoichi Miyahara , Hajime Ozaki Hajime Ozaki
Published: October 2002

Tunneling measurements were carried out to investigate the valence band structure of Pb1-x
EuxTe with x=0.038. A marked decrease in the dI/ dV has been observed in the energy range of Eu-4f states. It was found that the top edge of the Eu-4f states lies 0.13 eV below the top of the valence band for x=0.038.
In Situ Mass and Photoemission Studies of Fluorinated Polyimide Films Irradiated with an Electron Beam
Authors: Yamada-Maruo Yasuko , Tamamura Shigekuni Sasaki
Published: October 2002

Fluorinated polyimide films were irradiated in an ultrahigh vacuum with an electron beam. In situ mass analysis was carried out simultaneously and in situ photoemission studies were performed on surfaces modified by electron exposure at various electron beam energies and various sample currents. Based on the present data, the irradiation of electrons produces a fluorine-poor surface and an imide-ring opening, and the production rate was accelerated by raising the electron beam energy. An electron beam with low energy and low density is effective for changing the refractive index of the surface of fluorinated polyimide films with small strength change.
A Simple Graphic Method for Evaluating Densities and Energy Levels of Impurities in Semiconductor from Temperature Dependence of Majority-Carrier Concentration
Authors: Hideharu Matsuura Hideharu Matsuura , Kazuhide Sonoi Kazuhide Sonoi
Published: October 2002

A simple graphic method for impurity-level analysis of semiconductors is proposed. Because the concentration of majority carriers emitted from each impurity level increases monotonically with an increase of temperature (T), the product of 1/T and the total majority-carrier concentration has several peaks, and each peak results from the corresponding impurity level. Thus, from each peak value and the corresponding temperature, the density and energy level can be evaluated.
Effects of an Ultrathin Inserted Si Layer on Dislocation Nucleation in Ge/Si Heterostructures
Authors: Masaya Ichimura Masaya Ichimura
Published: October 2002

We theoretically investigate the effects of an ultrathin inserted Si layer on misfit dislocation nucleation in Ge/Si. The inserted layer does not significantly change the equilibrium critical thickness for dislocation nucleation, but it increases the energy barrier for dislocation nucleation at the surface. For example, a dislocation needs to surmount an energy barrier of about 0.65 eV/Å in order to nucleate at the surface of Ge/Si, but the energy barrier increases to about 0.8 eV/Å if a 2-monolayer-thick Si layer is inserted near the surface. Thus, the dislocation nucleation will be kinetically delayed by insertion of the Si-layer.
Spectrally Narrowed Operation of a Gain-Switched 690 nm GaInP/AlGaInP Fabry-Perot Laser by Self-Seeding Technique
Authors: Yasuhiro Uchiyama Yasuhiro Uchiyama , Masahiro Tsuchiya Masahiro Tsuchiya , Hai-Feng Liu Hai-Feng Liu , Takeshi Kamiya Takeshi Kamiya
Published: October 2002

Spectrally narrowed pulses from a gain-switched 690 nm GaInP/AlGaInP Fabry-Perot laser are successfully obtained by the self-seeding technique. A commercially available laser diode emits 48 ps pulses with a spectral width of 0.10 nm or less. This scheme will provide a compact and efficient light source for generation of ultraviolet light by nonlinear optical methods such as second-harmonic generation.
Ferromagnetic Tendency of TDAE-Fullerene-Conducting Polymer System
Authors: Kawai Tsuyoshi , Mizobuchi Hiroshi , Okazaki Shoji , Hisashi Araki Hisashi Araki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Magnetic behavior of tetra(diethylamino)ethylene-fullerene-conducting polymer systems has been studied by electron spin resonance as a function of temperature. A C60-doped poly(3-dodecylthiophene) film is further doped by tetra(diethylamino)ethylene and the temperature dependence of its spin susceptibility is explained by Curie-Weiss equation with positive Weiss temperature after heat treatment. Effect of heat treatment was discussed on the basis of aggregation and growth of C60-tetra(diethylamino)ethylene charge transfer complex within the conducting polymer matrix. A composite film of C60-tetra(diethylamino)ethylene powder and poly(3-dodecylthiophene) is also prepared and shows ferromagnetic electron spin resonance behavior with the transition temperature about 20 K.
Evolution of Current-Voltage Characteristics in Bi 2Sr 2CaCu 2O 8 Intrinsic Tunnel Josephson Junctions
Authors: Minoru Suzuki Minoru Suzuki , Yoshikazu Hidaka Yoshikazu Hidaka , Keiichi Tanabe Keiichi Tanabe , Shin-ichi Karimoto Shin-ichi Karimoto , Kazuichi Namekawa Kazuichi Namekawa
Published: October 2002

A series of unique current-voltage characteristics are observed as a function of temperature for a stack of 18 intrinsic tunnel Josephson junctions fabricated on an underdoped \BSCCO single crystal. The characteristics at low temperatures below T
c clearly show a superconducting energy gap of about 24 meV, which is suppressed significantly by the nonequilibrium superconductivity effect. On the other hand, the characteristics above T
c are nonlinear up to 180 K, which cannot be explained within the framework of conventional tunnel Josephson junctions. This nonlinearity is interpreted to provide evidence for the evolution of a pseudogap, or most likely a spin gap, in this system. The semiconductive temperature dependence of the c-axis resistivity is also explained consistently in terms of this pseudogap.
In0.38Ga0.62As/InAlGaAs/InGaP Strained Double Quantum Well Lasers on In0.21Ga0.79As Ternary Substrate
Authors: Shoji Hajime , Otsubo Koji , Kusunoki Toshihiro , Suzuki Takashi , Toru Uchida Toru Uchida , Hiroshi Ishikawa Hiroshi Ishikawa
Published: October 2002

An In0.21Ga0.79As ternary substrate has been fabricated using a newly developed multicomponent zone-growth method, and In0.38Ga0.62As/InAlGaAs/InGaP strained double quantum well lasers have been fabricated on the ternary substrate. Room temperature cw operation at a lasing wavelength longer than 1.2 µ m has been achieved on the ternary substrate for the first time. The lasers exhibited a low threshold current density of 280 A/cm2 and a characteristic temperature of 84 K, which were close to the designed values. It is also shown that the use of a wider band-gap barrier would enable a characteristic temperature higher than 150 K.
Biexciton Luminescence from GaN Epitaxial Layers
Authors: Okada Kiyohiko , Yamada Yoichi , Taguchi Tsunemasa , Sasaki Fumio , Kobayashi Shunsuke , Tani Toshiro , Nakamura Shuji , Shinomiya Gen-ichi
Published: October 2002

Excitonic luminescence from GaN epitaxial layers has been studied under high-density excitation. The first experimental evidence for biexciton formation in GaN was obtained. The binding energy of the biexciton was estimated to be 5.3 meV. Therefore, the ratio of biexciton binding energy to exciton binding energy was approximately 0.19.
Silicon Single Crystal Fiber Growth by Micro Pulling Down Method
Authors: Shimamura Kiyoshi , Uda Satoshi , Yamada Tohru , Sakaguchi Susumu , Tsuguo Fukuda Tsuguo Fukuda
Published: October 2002

Silicon single crystal fibers with a constant diameter as small as 200 µ m have been successfully grown by the micro pulling down technique. Grown crystal fibers are uniform in shape and contain a large defect-free volume. Basic parameters for stable growth were discussed in association with the conservation of mass and heat as well as the meniscus stability of the molten zone.
Dimerization Process in Alkanethiol Self-Assembled Monolayer on Au(111)
Authors: Nishida Naoki , Hara Masahiko , Hiroyuki Sasabe Hiroyuki Sasabe , Wolfgang Knoll Wolfgang Knoll
Published: October 2002

Desorption kinetics of alkanethiol self-assembled monolayer (SAM) on an Au(111) surface is studied by thermal desorption spectroscopy (TDS) using a quadrupole mass spectrometer. TDS reveals for the first time that SAM desorbs to form a dimer, dialkyl disulfide molecule from the Au surface with a desorption activation energy of 32 kcal/mol. This result suggests that there exists a dimerization process of SAM molecules on the Au surface, which has been predicted by Fenter et al.. [Science 266 (1994) 1216] through diffraction studies.
Deep Levels in SnTe-Doped GaSb Grown on GaAs by Molecular Beam Epitaxy
Authors: Chen Jenn-Fang , Nie-Chuan Chen Nie-Chuan Chen , Hung-Sing Liu Hung-Sing Liu
Published: October 2002

A dominant deep level with an activation energy of 0.23–0.26 eV was observed by admittance spectroscopy in SnTe-doped GaSb layers grown directly on GaAs substrates by molecular beam epitaxy (MBE). The Sb4/Ga flux ratio was found to affect the Hall mobility and the concentration of the deep level in a similar way, with an optimal beam equivalent pressure ratio of around 7 obtained for GaSb grown at 550° C, which should correspond to the lowest ratio at which a Sb-stabilized surface reconstruction can be maintained. This electron level is commonly detected in n-type (SnTe-, S- and Te-doped) GaSb, but not in undoped p-type GaSb, suggesting that the level is not a simple native defect, but may be connected with the impurity used for n-type doping of GaSb.
Contribution of Floating Bonds to Photocreation of Defects in a-Si:H
Authors: Tatsuo Shimizu Tatsuo Shimizu , Minoru Kumeda Minoru Kumeda
Published: October 2002

We propose a model for the metastabilization of photocreated dangling bonds in a-Si:H based on easily movable fivefold-coordinated Si atoms (floating bonds). We also discuss the contribution of negatively charged floating bonds to the light-induced ESR at low temperature.
Study on Adsorption Behavior of Organic Contaminations on Silicon Surface by Gas Chromatography/Mass Spectrometry
Authors: Takahagi Takayuki , Shingubara Shoso , Sakaue Hiroyuki , Hoshino Kunihiro , Yashima Hiroshi
Published: October 2002

We successfully revealed the adsorption behavior of actual organic contaminations on a Si wafer surface using a gas chromatograph/mass spectrometer system with a quartz heat-desorption chamber and a two-step concentration trap. Antioxidants contained in the wafer case material and a monomer and an oligomer from the plastic vessel material used in the production process were confirmed to contaminate the surface of the Si wafer. Organic materials in the atmosphere, such as organic solvents and plasticizers, were also observed to adsorb on the surface during an exposure to a laboratory atmosphere for a few hours. The results suggest that completely surface-cleaned Si wafers should be stored in a stocker in which the amount of organic species in the atmosphere is well controlled.
Observation of the Electric-Dipole-Forbidden States in Polydiacetylene by Means of Resonance Second-Harmonic Generation Spectroscopy
Authors: Takaaki Manaka Takaaki Manaka , Toshiki Yamada Toshiki Yamada , Hajime Hoshi Hajime Hoshi , Ken Ishikawa Ken Ishikawa , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: October 2002

We have observed resonance second-harmonic generation (SHG) spectra in polydiacetylene (poly [5,7-dodecadiyne-1,12-diyl-bis-ethylurethane], 4U2 for short) films. The resonant peak appears on the high-energy side of the linear absorption peak. The peak observed in SHG spectra is assigned to an A
g exciton state, and the linear absorption peak to the lowest B
u exciton state. The observation of the dipole-forbidden A
g state originates from the resonance enhancement of SHG due to an electric quadrupole transition at the SH frequency region. Thus, the resonance SHG technique serves as a powerful tool for investigating dipole-forbidden states in centrosymmetric media such as π-conjugated polymers. The advantages of this method compared with other methods such as two-photon absorption and electroreflectance will be discussed.
Monolithic Fabrication and Electrical Characteristics of Polycrystalline Silicon Field Emitters and Thin Film Transistor
Authors: Hashiguchi Gen , Mimura Hidenori , Fujita Hiroyuki
Published: October 2002

We have developed a novel monolithic fabrication method for polycrystalline silicon (poly-Si) field emitters and a poly-Si thin film transistor (TFT). Poly-Si field emitters were fabricated using a mold transfer process, which allows a TFT to be fabricated under the field emitters and saves space for emitter fabrication. We have also demonstrated successful control of the field emission using the monolithically fabricated TFT.
A New Metal-Oxide-Semiconductor Field-Effect-Transistor-Structured Si Field Emitter Tip
Authors: Hirano Takayuki , Seigo Kanemaru Seigo Kanemaru , Junji Itoh Junji Itoh
Published: October 2002

A new current-controllable silicon field emitter tip with a metal-oxide-semiconductor field-effect-transistor (MOSFET) structure is proposed and demonstrated. The device has a simple structure in which a conical Si tip is made in the drain region of a MOSFET. The gate plays two roles; one is that of a conventional extraction electrode and the other is that of a control gate for the drain current supplied to the tip. Experimental results showed that the emission current was well controlled by the drain current at a gate voltage of around 80 V. Quite stable emission of about 0.8 µ A was obtained with a single tip at the above gate voltage.