bluuebunny/crossref_metadata_2025 huggingface dataset:
Facet Degradation of AlGaInP Visible Semiconductor Lasers with Facet Passivation
Authors: Fukushima Takehiro , Furuya Akira , Kito Yasuhiro , Sugano Mami , Hisao Sudo Hisao Sudo , Toshiyuki Tanahashi Toshiyuki Tanahashi
Published: October 2002

We studied the reliability of AlGaInP visible semiconductor lasers with three different coating films. The facet degradation was analyzed using an optical microscope and the micro-auger electron spectroscopy (µ-AES) sputter profiling method. We found that the degradation is associated with facet erosion. We discussed the causes of facet erosion.
Soft X-Ray Emission Spectroscopic Analysis of Pt Silicides (Pt2Si, PtSi)
Authors: Yamauchi Shoichi , Hirai Masaaki , Kusaka Masahiko , Iwami Motohiro , Nakamura Hatsuo , Hisayoshi Ohshima Hisayoshi Ohshima , Tadashi Hattori Tadashi Hattori
Published: October 2002

We have studied the partial valence band density of states (VB-DOS) of Pt-silicides by using soft X-ray emission spectroscopy (SXES). Si Kβ emission spectra of Pt2Si and PtSi provide information on the Sippartial VB-DOS, showing the clear bonding and antibonding states. The contribution of Sisand/ordstates to the upper part of VB-DOS has also been observed from the Si L2,3emission spectra of Pt2Si and PtSi. Such a contribution of the Sisand/ordstate to the upper part of the VB-DOS has not been predicted by previous theoretical studies.
Structure of a-Si and Its Transient Phases upon Rapid Heating
Authors: Masaki Yuichi , Qu Wei-Feng , Masakuni Suzuki Masakuni Suzuki , Akio Kitagawa Akio Kitagawa
Published: October 2002

To explain the anomalous phenomena which have been observed in rapid heating processes, a structural model of a-Si and a model for its transient phases have been proposed. In the structural model, a-Si was assumed to be composed of many small regions with different free-energy levels. It was thought that a-Si transformed to a new phase in which both liquid Si and solid a-Si clusters coexisted when the a-Si was rapidly heated so as to avoid crystallisation. From the enhanced diffusion data previously reported for rapid thermal annealing processes, the viscosity of the partially molten a-Si at around 1000°C was estimated to be 107–108 mPa·s based on our model.
Characterization and Fabrication of Crater-Shaped Silicon Field Emitters
Authors: Sawada Kazuaki , Kun Ji Kun Ji , Takao Ando Takao Ando
Published: October 2002

Silicon field emitter arrays with crater-shaped structure applicable to imaging devices were proposed. The emission current from crater-shaped emitters is larger than that from cone-shaped emitters whose sizes and curvature are the same as those of crater-shaped emitters. To estimate the ability to emit electrons, a method using the satu- ration phenomenon of an emission current of a p-type silicon field emitter was proposed. It was found that the crater-shaped silicon field emitter is expected to emit 70 times higher current than that from the cone-shaped emitter at the same electric field on the tip of the emitter.
Gas-Source Molecular Beam Epitaxy of GaNxAs1-x Using a N Radical as the N Source
Authors: Kondow Masahiko , Uomi Kazuhisa , Kazuhiko Hosomi Kazuhiko Hosomi , Teruo Mozume Teruo Mozume
Published: October 2002

We propose the application of GaNAs as a novel material fabricated on a Si wafer. It is a direct-transition type semiconductor, and can be lattice-matched to Si. Therefore, it is valid for use in the active region of light-emitting devices fabricated on Si. In this letter, GaNAs with a low N content is grown on a GaAs wafer to explore the gas-source molecular beam epitaxy under which a N radical is used as the N source. As a consequence, GaNAs with a N content up to 1.5% is grown, even though the conductance of the N-radical beam cell is fixed at a very low value. The bowing parameter of the bandgap is experimentally evaluated at 18 eV.
Laser-Ablation Mechanism of Sr Metal Investigated by Time-of-Flight Mass Spectroscopy
Authors: Nishikawa Hiroaki , Kanai Masaki , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: October 2002

In order to investigate the laser ablation mechanism, the velocity distribution and amount of Sr+ produced by ArF excimer laser irradiation of Sr metal have been measured by time-of-flight (TOF) mass spectroscopy. The velocity distribution of Sr+ agrees with the Maxwell-Boltzmann distribution corrected by the center-of-mass velocity. The relationship between the amount of produced ions and laser fluence suggests that Sr+ is produced by a 4-photon process. Based on these experimental results, a simple model for the laser ablation mechanism of Sr metal is proposed.
Dielectric Dispersion in Ferrielectric Phase of Antiferroelectric Liquid Crystal
Authors: Hiller Steffen , Pikin Sergei A. , Haase Wolfgang , Goodby John W. , Nishiyama Isa
Published: October 2002

We studied the dielectric behavior in the ferroelectric SmC* and ferrielectric SmCγ
* phases of the antiferroelectric liquid crystal (R)-1-methylheptyl-4-( 4′′-n-dodecyloxybiphenyl- 4′ carbonoyloxy)-3-fluoro-benzoate. In the SmCγ
* phase, 3 dielectric relaxations were recognized in the frequency range under consideration. The 2 relaxation processes at low frequency with high dielectric loss were attributed to azimuthal fluctuation of the molecules around the cone angle ϕ. Those relaxations are investigated as functions of temperature and applied bias electric field. Besides the 2 low-frequency loss processes, one additional loss process with weak intensity was observed.
Ferroelectricity of Solid Solution Pb[(Yb1/2Nb1/2)1/3Zr2/3]O3
Authors: Masaru Yokosuka Masaru Yokosuka
Published: October 2002

Studies were conducted on the ferroelectric properties of Pb[(Yb1/2Nb1/2)1/3Zr2/3]O3 which is considered to be a solid solution consisting of antiferroelectric compounds, Pb(Yb1/2Nb1/2)O3 and PbZrO3, in the mole ratio of 1:2. The crystal structure was determined to be perovskite type of tetragonal symmetry with lattice constants a
T=4.158 Å and c
T=4.116 Å. The Curie temperature was found to be 150° C. The remanent polarization, P
r=6.8 µC/cm2, and the electromechanical coupling factor, k
33=0.20, were obtained at room temperature. Finally, the nature of the ferroelectricity of Pb[(Yb1/2Nb1/2)1/3Zr2/3]O3 was briefly discussed.
Properties of Voltage Holding Ratios of Liquid Crystal Cells Using Organic-Solvent-Soluble Polyimide Alignment Films
Authors: Nishikawa Michinori , Suganuma Takayoshi , Tsuda Yusuke , Bessho Nobuo , Iimura Yasufumi , Kobayashi Shunsuke
Published: October 2002

We have synthesized organic-solvent-soluble polyimides containing various diamine moieties. The voltage holding ratios of liquid crystal (LC) cells using these polyimides as alignment films have been investigated. The results show that the structures of polyimides considerably affect the characteristics of the voltage holding ratios of LC cells. It is shown that the large polarization in polyimides, which is evaluated from the calculation of partial atomic charges of diamines and the capacitance-voltage measurement of LC cells, gives rise to lower voltage holding ratios of LC cells.
Enhanced Oxidation of Ion-Implanted Si-Face of 6H-SiC
Authors: Katsunori Ueno Katsunori Ueno , Yasukazu Seki Yasukazu Seki
Published: October 2002

The Si-face of 6H-SiC is slowly oxidized even at temperatures as high as 1200° C in steam. We found that the oxidation rate of the implanted Si-face is several times faster than that of the non-implanted face. This oxidation rate strongly depends on the mass number of the implanted ion, and on the acceleration energy. Based on the study of the oxidation rate, dosage and acceleration energy dependence, this phenomenon is concluded to be induced by the amorphous layer of the implanted region. We demonstrated the selective oxidation technique utilizing this phenomenon in its application to various devices.
Characteristics and Alternating Modulation of Y1Ba2Cu3O7-y Superconducting Flux Flow Transistors
Authors: Zhongmin Wen Zhongmin Wen , Hitoshi Abe Hitoshi Abe
Published: October 2002

The characteristics and the measurement of lower critical magnetic field of Y1Ba2Cu3O7-
y

superconducting flux flow transistors (SFFTs) are reported. The devices are fabricated by forming the channels of vortex flow onto step edge of SrTiO3 substrates. Reproducible transistor behaviors are observed, and the operation temperature is over 70 K. A method for measuring the lower critical field H(c1) from the magnetic field of both control current and bias current is also presented. We find that H(c1) of the Y1Ba2Cu3O7-
y

SFFT is 0.9 G at 70 K using this method. Alternating modulation of the device is investigated, which shows transresistances of over 10 Ω and output resistances of about 5 Ω.
Reverse Annealing of Arsenic-Implanted Low-Pressure Chemical Vapor Deposition (LPCVD) Amorphous-Silicon Films
Authors: Tsai Meng-Jin , Fang-Shin Wang Fang-Shin Wang , Huang-Chung Cheng Huang-Chung Cheng
Published: October 2002

The reverse annealing of arsenic-implanted amorphous-silicon films has been observed. The dose dependence of this phenomenon is also investigated. For the specimens implanted with the dosage of 4×1014 ion/cm2, the sheet resistances show an increase in the annealing temperature range from 700 to 850°C, which is attributed to the segregation of the activated dopants to the grain boundaries. This reverse annealing phenomenon is less prominent and the turnaround temperature is lower for the implantation dosage of 2×1015 ion/cm2, which is attributed to the effects of dopant segregation which decreases with increasing implantation dosage. Consequently, this reverse annealing phenomenon was not observed for the case of dosage of 1×1016 ion/cm2.
Stability of Metallofullerene LaC82 on UV Light Irradiation
Authors: Ishibashi Masayoshi , Tomioka Yasushi , Taniguchi Yoshio , Suzuki Shinzo , Wakabayashi Tomonari , Kojima Yasuhiko , Kikuchi Koichi , Achiba Yohji
Published: October 2002

The effect of UV light on the stability of metallofullerenes containing lanthanum was investigated using laser desorption time-of-flight mass spectrometry and ESR. The decomposition rate of LaC82 in toluene solution was about 100 times faster than that of C60. Moreover, decomposition of both metallofullerene and C60 toluene solutions induced by UV light irradiation in air would mainly occur without oxide formation. In these decomposition reactions by UV light irradiation, both dissolved oxygen and photo excited toluene molecules would play important roles.
Superparamagnetic Nanocomposite of Silver/Iron-Oxide by Inert Gas Condensation
Authors: Takao Yamamoto Takao Yamamoto , Robert D. Shull Robert D. Shull , Prabhakar R. Bandaru Prabhakar R. Bandaru , Frederic Cosandey Frederic Cosandey , Horst W. Hahn Horst W. Hahn
Published: October 2002

A superparamagnetic nanocomposite of silver and iron oxide was synthesized by gas condensation. The procedure involved (1) coevaporation of silver and iron, (2) in situ oxidation of iron particles, (3) in situ compaction, and (4) post-annealing in an inert or an oxidizing atmosphere. The magnetization plots against H/T fell on a single curve from room temperature to 160 K, thereby providing evidence of superparamagnetism. Annealing treatment modifies the effective magnetic moment size and saturation value of magnetization. The present process is a potential synthesis route for magnetic nanocomposites useful for applications such as magnetic refrigeration, recording and permanent magnets.
Pb(Mg1/3Nb2/3)O3 Ceramics Produced by Modified Two-Stage Calcination Process
Authors: Liou Yi-Cheng , Long Wu Long Wu , Shyh-Shan Liou Shyh-Shan Liou
Published: October 2002

Pyrochlore-free lead magnesium niobate ceramics produced by a modified two-stage calcination process are studied. One calcination step of the two-stage calcination process was omitted in this method. Without calcining, columbite MgNb2O6 and PbO were sintered directly to form pyrochlore-free and dense Pb(Mg1/3Nb2/3)O3 ceramics. The grain size is about 6 µm and the dielectric constant reaches 17000 at -9°C under 1 kHz. An increase in sintering temperature resulted in an increase in maximum dielectric constant.
Observation of Threefold Symmetry Images due to a Point Defect on a Graphite Surface Using Scanning Tunneling Microscope (STM)
Authors: Kondo Seiichi , Mark Lutwyche Mark Lutwyche , Yasuo Wada Yasuo Wada
Published: October 2002

This paper reports an observation of a point defect on a graphite surface with a threefold-symmetric electronic perturbation, which is a required characteristic of a point defect predicted by a simulation. A scanning tunneling microscope (STM) was used. Due to the covalent system of graphite, the propagation length of the electronic perturbation is only one tenth of that in the free electron system and its symmetry reflects the crystallographic symmetry. By considering the effects of the electronic enhanced dimers, this electronic perturbation can be interpreted as an initial formation stage of a (√3×√ 3)R30° superlattice which is often observed in the neighborhood of larger defects.
Improved Negative Differential Resistance Characteristics in Surface Tunnel Transistors
Authors: Tetsuya Uemura Tetsuya Uemura , Toshio Baba Toshio Baba
Published: October 2002

We propose and demonstrate a new type of Surface Tunnel Transistor (STT) which displays improved negative differential resistance (NDR) characteristics. In this device, called channel-doped STT (CD-STT), the channel region is direclly doped with donors in order to increase the channel carrier density. A peak current is obtained that is 103times larger than that of a conventional STT. To reduce the valley current further, a blocking layer consisting of an i-GaAs is inserted at the gate/drain overlap region. The resulting device, called blocking layer inserted STT (BLI-STT), exhibits excellent NDR characteristics with a peak-to-valley ratio (PVR) of 4.8 at room temperature, a value which is more than 4 times larger than that of a conventional STT.
Vibrational Modes of C60 Fullerene on Si(111)7×7 Surface: Estimation of Charge Transfer from Silicon Dangling Bonds to C60 Molecules
Authors: Suto Shozo , Kasuya Atsuo , Ikeno Osamu , Hu Chang-Wu , Wawro Andrzej , Nishitani Ryusuke , Nishina Takenari Goto
Published: October 2002

We have investigated vibrational modes of C60 monolayer film adsorbed on the Si(111)7×7 surface using high-resolution electron-energy-loss spectroscopy in combination with scanning tunneling microscopy. The differences in energies and in oscillator strengths from a thick C60 film (i.e., bulk C60) are discussed in terms of the charge transfer from silicon dangling bonds to C60 molecules. The amount of charge transfer is estimated to be 1±1 electron(s) compared with the infrared absorption spectra of alkaline-doped C60 fullerides and with the weak electron-molecular-vibration coupling calculation.
Novel Technique of Laser Through-Hole Drilling in Teflon
Authors: Haba Belgacem , Yukio Morishige Yukio Morishige , Shunji Kishida Shunji Kishida
Published: October 2002

A novel technique of laser drilling of reinforced Teflon films with SiO2 particles is demonstrated. The new process consists of three simple steps. First, 300 Å of gold is deposited on Teflon to allow laser absorption. Second, drilling is done by pulsed irradiation at a rate of one hole per pulse. At this stage the Teflon is only modified by the laser irradiation. Third, the modified Teflon is removed by ultrasonic cleaning, leaving behind clean through-holes of 50 µm in diameter. A potential drilling speed as high as 60000 holes/min with fairly high spatial resolution is the main attraction of this simple technique.
All-Optical Absorptive and Dispersive Bistabilities in Luminescence of a Thin CdS Film
Authors: Bruno Ullrich Bruno Ullrich , Takayoshi Kobayashi Takayoshi Kobayashi
Published: October 2002

All-optical photo-thermal bistabilities in the near infrared luminescence (800 nm) of a thin ( 5.5 µm) spray-pyrolyzed CdS film are studied with the 514.5 nm line of an argon laser. We report the first observation of both dispersive and absorptive luminescence bistabilities in the same CdS film. The temperature dependence of the luminescence intensity and self-focusing are found to be the origins of absorptive and dispersive luminescence bistabilities, respectively. Furthermore, it is demonstrated that the shape of the bistable response of the luminescence depends crucially on the entrance slit width of the monochromator.
Effect of pH Buffer on Electrochemical Deposition of Calcium Phosphate
Authors: Maruno Seiji Ban
Published: October 2002

Calcium phosphate coatings containing carbonate apatite were deposited on pure titanium plate by an electrochemical method in the electrolytes containing different amounts of Ca and P with and without trishydroxyaminomethane, a pH buffer. Results suggest that addition of pH buffer into the electrolyte has a pronounced effect on the amount of products on the titanium electrode, whereas the composition of the products is nearly independent of the Ca/P ratio in the electrolyte.
High Spatial Resolution Elemental Mapping of Multilayers Using a Field Emission Transmission Electron Microscope Equipped with an Imaging Filter
Authors: Kimoto Koji , Hirano Tatsumi , Hoshiya Katsuhisa Usami
Published: October 2002

Elemental mapping with about 1 nm spatial resolution has been achieved using a field emission transmission electron microscope (FE-TEM) equipped with an imaging filter. Chromium mapping is carried out with the Cr r
m
L
2,3 core-loss edge (575 eV). Chromium layers a few nanometers in thickness can be clearly observed. The obtained thicknesses are compared with results of X-ray reflectivity, and they show good agreement.
Near-Field Scanning Optical Microscope with a Laser Trapped Probe
Authors: Kawata Satoshi , Yasushi Inouye Yasushi Inouye , Tadao Sugiura Tadao Sugiura
Published: October 2002

We made an experiment of near-field microscopic imaging using a laser-beam trapped probe. Differently from a conventional near-field (and/or photon-tunneling) scanning optical microscope, the probe is physically isolated from the scanning microscope system; it is trapped and scanned on the sample surface by the radiation force of near-infrared laser beam. The distance between the probe and the sample surface is maintained to be constant (zero) during scanning. Another laser beam for microscopic imaging is incident on the sample surface in the condition of total internal reflection; the probe on the sample couples with the photons localized near the sample surface as the evanescent filed and scatters out. The scattered photons are collected through an microscope objective lens, which is the same lens as the one used for focusing the infrared laser beam on the probe. A near-field image of the sample surface is formed, as the probe is laterally scanned on the sample. The experimental setup of the proposed microscope is described and the image data obtained with the developed microscope are shown for refractive samples and fluorescent samples with sub micrometer structure.
Resistivity Study of P-, B-, and BF2-Implanted Polycrystalline Si1-xGex Films with Subsequent Annealing
Authors: Noguchi Takashi , Tsai Julie A. , Andrew J. Tang Andrew J. Tang , Rafael Reif Rafael Reif
Published: October 2002

Thin polycrystalline Si1-
x

Ge

x

films with low resistivities have been achieved by low pressure chemical vapor deposition (LPCVD) with subsequent ion implantation and thermal annealing. The sheet resistance decreased drastically as the Ge content increased to 36 atomic percent. Even at a moderate dose of 1.5×1015/cm2, a resistivity of 8.3×10-4 Ω·cm was obtained for B+-doped samples and 3.8×10-4 Ω·cm for P+-doped samples. Furthermore, stability of the resistivity values after sintering was confirmed. Poly-Si1-
x

Ge

x

can be used for new applications in Si LSIs such as fine-patterned MOS gates or germanosilicide interconnects.
Strong Photoluminescence from the Reaction Product of Erbium and Oxygen on Silicon Crystal
Authors: Masashi Suezawa Masashi Suezawa , Koji Sumino Koji Sumino
Published: October 2002

Photoluminescence spectra around 1.5 µm from silicon (Si) doped with erbium (Er) by various methods have been studied. The doping methods that were adopted were annealing after painting of Er(NO3)3 solutions and evaporation of Er on Si surface, and annealing of specimens in the Er vapour. Strong photoluminescence similar to that of Er2O3 was observed only from the damaged surface of n-type Czochralski-grown Si when Er was doped with the last method. Analysis of the damaged surface by the method of electron spectroscopy for chemical analysis (ESCA) showed that Er2O3 was generated on the surface of n-type Cz.Si.
Manufacture of YBa2Cu3O7-x Superconductor by Using a Neodymium:Yttrium Alumina Garnet Laser
Authors: Jang Guneik , Mukherjee Kali , Hogi Kim Hogi Kim
Published: October 2002

Y–Ba–Cu–O superconductor powder was calcined by using a low-power Nd:YAG laser for raid calcination of the initial 1:2:3 mixture in an air atmosphere. This new powder processing technique greatly reduces processing time, since no furnace is required for the calcination process. In this paper the observations of bulk superconductor processed by two different techniques, i.e., by conventional and laser processing are compared.
Metalorganic Chemical Vapor Deposition of ZnO Using D2O as Oxidant
Authors: Wenas Wilson W. , Yamada Akira , Takahashi Makoto Konagai
Published: October 2002

ZnO films with low resistivity and high transparency in a wavelength range of 400 nm–1300 nm were successfully grown by the metalorganic chemical vapor deposition (MOCVD) technique using D2O as a new oxidant for diethylzinc on glass substrates. It was also found that the crystal orientation of the films was strongly dependent on the substrate temperature. By employing both D2O and H2O as oxidants for diethylzinc, the surface morphology of low-resistivity ZnO films could be modified. The obtained films are suitable as transparent conducting materials.
Excimer-Laser Removal of SiO2 Patterns from GaAs Substrates
Authors: Lu Yong-Feng , Takai Mikio , Shiokawa Takao , Aoyagi Yoshinobu
Published: October 2002

SiO2 patterns on GaAs substrates can be completely removed by KrF excimer-laser irradiation in air. The substrate surface is found to be dean, without residual SiO2 patterns or other contaminants. Free-standing SiO2 microstripes can be formed by this method. This technique provides an efficient dry process to remove SiO2 patterns on GaAs substrates, instead of the wet etching process. The mechanisms to peel off the SiO2 patterns from the GaAs substrate are considered to involve direct momentum transfer, photodecomposition of the interface substance, and thermal expansion of the substrate.
Control of Floating Potential in an Electron-Beam-Excited Plasma
Authors: Manabu Hamagaki Manabu Hamagaki , Tamio Hara Tamio Hara
Published: October 2002

Control of the floating potential is demonstrated experimentally in a high-density reactive plasma without using external DC or RF bias. The difference between the floating potential and the space potential in an electron-beam-excited plasma (EBEP) can be easily controlled in the range of 20–90 V by changing the accelerating voltage of the electron beam or the angle between the electron beam and the probe surface.
A New Si Doping Source for GaAs Growth by Molecular Beam Epitaxy
Authors: Horikoshi Yoshiji , Fahy Mike R. , Kawashima Minoru , Furukawa Kazuaki , Masaie Fujino Masaie Fujino , Nobuo Matsumoto Nobuo Matsumoto
Published: October 2002

A new Si cluster material, tertiary-butyloctasilacubane (tBuSi)8,
is used as an efficient Si doping source for molecular beam epitaxy of GaAs.
The vapor pressure of this material varies according to an activation energy
of 1.51 eV. A Si concentration of 2×1020/cm3 is obtained at
a Si cluster cell temperature of 210°C and a GaAs growth rate of
1 µm/h. Although the grown layers suffer from heavy carbon contamination
from the Si cluster, this problem can be alleviated by increasing the
substrate temperature.
Step Coverage Analysis for Hexamethyldisiloxane and Ozone Atmospheric Pressure Chemical Vapor Deposition
Authors: Fujino Katsuhiro , Egashira Yasuyuki , Shimogaki Yukihiro , Komiyama Hiroshi
Published: October 2002

Hexamethyldisiloxane (HMDSO) and ozone atmospheric pressure chemical vapor deposition (AP CVD) presents good step coverage. Silicon trench step coverage has been analyzed for this CVD using a one-dimensional gas diffusion model. The calculated step coverage exhibited the best fit when the sticking probability of HMDSO molecules is 0.002, causing the good step coverage. The gas phase concentration profiles were calculated using numerical simulation. The estimation of the rate-determining step indicated that HMDSO diffusion limited the CVD reaction rate and HMDSO itself participated directly in film formation.
Multiphonon Raman Scattering Enhanced by Resonance with Band Gap Ag Luminescence State in Trans-Polyacetylene
Authors: Watanabe Toshio , Kubo Takaya , Ishikawa Ken , Hideo Takezoe Hideo Takezoe , Atuso Fukuda Atuso Fukuda
Published: October 2002

Emission spectra excited in the exciton forming absorption region (1.42–1.71 eV) of trans-polyacetylene have been obtained at room temperature, 77 K and 4.2 K. The overtones and combinations of fundamentals are remarkably enhanced only when they overlap with the near-infrared luminescence peaking at 1.24 eV. These facts suggest the similarity between trans- and cis- (CH)

x

in optical and photoelectric responses at least near their respective intrinsic absorption characterized by the triplet vibronic structure.
Wide Band Gap Si:H at Low H-Content Prepared by Interrupted Grown and H-Plasma Treatment
Authors: Debajyoti Das Debajyoti Das
Published: October 2002

Alternating the deposition of thin layers of a-Si:H at 100°C and exposure to r.f. H-plasma periodically, an widening of optical band gap by 20% along with the reduction in hydrogen content by 80% was observed in stacked layers. Interrupted growth and H-plasma treatment has been established as an effective technique for the elimination of hydrogen from Si:H network, however, simultaneous widening of optical band gap appears to be an interesting feature related to Nano-crystallization and quantum size effect in hydrogenated binary alloy.
Fluctuation of the Electrical Conductivity Associated with the Glass Transition of xKNO3·(100-x)Sr(NO3)2 Glasses
Authors: Nishida Tetsuaki , Matsumoto Masakazu Ohara
Published: October 2002

Electric conductivity σ of x KNO3·(100- x)Sr(NO3)2 glasses (22≤x ≤60) shows anomalous behavior associated with the glass transition; it becomes almost constant at around the “onset” temperature T
g(on), irrespective of the increase in the temperature, and then increases steeply. At the end of glass transition, σ drops rapidly due to a decrease in the mobility of carrier (K+) as a result of partial crystallization. In the temperature region below T
g(on), the activation energy E
a for the K+-conduction increases linearly from 0.30 to 1.57 eV with an increasing KNO3 content, being consistent with a linear increase in the density from 2.11 to 2.29 g·cm-3. On the contrary, E
a decreases gradually from 2.14 to 0.78 eV with an increasing KNO3 content in the region above the “end” temperature T
g(off).
Dynamic Characteristics of Liquid Helium Breakdown Induced by Quench Phenomena of ac Superconducting Wire
Authors: Hirose Makoto , Wakita Mikio , Goshima Hisashi , Hayakawa Naoki , Hikita Masayuki , Uchida Katsumi , Hitoshi Okubo Hitoshi Okubo
Published: October 2002

We measured dynamic breakdown voltage V
D of liquid helium (LHe) induced by quench phenomena of a superconducting wire under high electric field stress. V
D was defined as the minimum value of the applied voltage below which the breakdown was no longer induced with the quench. Experimental results revealed that V
D fell down drastically compared with the static breakdown voltage V
S without the quench. We also found that the delay time T
d of millisecond order existed from quench onset to breakdown. V
D and T
d depended on the gap length. Moreover, we observed the behavior of thermal bubbles in LHe which were generated after the quench onset using a fiberscope monitoring system.
Quantized Conductance in InGaAs Point Contacts at High Temperatures
Authors: Bever Thomas , Yoshiro Hirayama Yoshiro Hirayama , Seigo Tarucha Seigo Tarucha
Published: October 2002

We used focused ion beam insulation writing to fabricate quantum point contacts in the two-dimensional electron gas of an InGaAs/InAlAs heterostructure. The conductance as a function of voltage on an adjacent in-plane gate exhibited steps for temperatures up to 60 K. From the temperature and source-drain voltage and magnetic field dependence of the conductance steps, we estimated the one-dimensional subband spacing to be 15 meV.
Kinetics of Magnetic Relaxation and Determination of Activation Energy in High-Tc Superconductors
Authors: Xiao-Guang Li Xiao-Guang Li , Ryu Kobayashi Ryu Kobayashi , Yasutoshi Kotaka Yasutoshi Kotaka , Jun-ichi Shimoyama Jun-ichi Shimoyama , Kohji Kishio Kohji Kishio
Published: October 2002

The deviation of magnetic relaxation from the usual logarithmic decay in type-II superconductors was analyzed in terms of the first-order kinetic relaxation process. The theoretical and experimental results show that the relaxation of magnetic induction B obeys the power law equation, namely, B=B
0 +B
1
t
-α, where B
0 is the \lq\lqequilibrium" value of the magnetic induction, and B
1 and α are field- and temperature-dependent constants. It was found that α, which is related to the pinning potential barrier, varies with temperature following the Arrhenius-type thermal activation behavior. Based on the present phenomenological theory, the current J dependence of the apparent activation energy U
a is discussed by using the relaxation data of a Bi2.1Sr1.8Ca1.0Cu2.0O8+δ single crystal.
Effects of Substrate Misorientation and Zn Doping Characteristics on the Performance of AlGaInP Visible Light-Emitting Diodes
Authors: Lin Jyh-Feng , Wu Meng-Chyi , Jou Ming-Jiuun , Chang Chuan-Ming , Lee Biing-Jye
Published: October 2002

Effects of substrate misorientation and Zn doping characteristics on the device performance of AlGaInP double-heterostructure light-emitting diodes are described. The light output power is found to be strongly dependent on the Zn concentration. The degradation of light output, which was caused by the increase in the number of Zn atoms, is investigated by photoluminescence and electroluminescence measurements. The emission properties can be improved by optimizing the growth of AlGaInP on an intentionally misoriented substrate and the Zn-doping level in the p-cladding layer. The external quantum efficiency of 3.5% at 618 nm can be obtained from the optimized LEDs with a 7.5-µm-thick GaP window layer.
Strongly Directed Emission from Controlled-Spontaneous-Emission Electroluminescent Diodes with Europium Complex as an Emitter
Authors: Takada Noriyuki , Tetsuo Tsutsui Tetsuo Tsutsui , Shogo Saito Shogo Saito
Published: October 2002

Multilayer electroluminescent diodes with sharp red emission were fabricated using a new europium complex as an emitter. Microcavity structures were introduced into the EL diodes with sharp red emission. The device structure consisted of a dielectric reflector composed of SiO2/TiO2 bilayers, an indium-tin-oxide electrode, a hole transport layer, a europium complex as an emission layer, an electron transport layer and a MgAg electrode. The dielectric reflector and the MgAg metal electrode constituted a planer microcavity, and sharply directed emission from the europium complex was observed when operated under dc drive voltage. The relationship between emission angle and the size of the microcavity was discussed.
Effect of Background Gas Pressure on Evaporation of Oxides from Sb-Doped Si Melt
Authors: Huang Xinming , Terashima Kazutaka , Koji Izunome Koji Izunome , Shigeyuki Kimura Shigeyuki Kimura
Published: October 2002

Evaporation losses of oxide species from undoped and Sb-doped Si melt in a silica crucible were measured by the thermogravimetric method. The melts were maintained at 1450° C under an atmosphere of pure Ar at pressures ranging from 100 to 780 Torr. The evaporation rate of all species decreased with increasing Ar pressure, although the pressure dependence of the evaporation rate was species-dependent. Increasing the Ar pressure from 100 to 780 Torr resulted in a 50% decrease in the SiO evaporation rate, whereas, over the same pressure range, the evaporation rate of Sb2O decreased by only 17%. We therefore conclude that the pressure of the background gas over a melt can be used to control the evaporation of oxide species from Si melts.
Effect of Residual Gases on Residue Formation during Tungsten/TiN/Ti Etching Using SF6 and Cl2 Gas Chemistry
Authors: Ahn Tae Hyuk , Nam Shin Woo , Kyung Jin Min Kyung Jin Min , Cheol Chung Cheol Chung
Published: October 2002

Residual gas-induced polymeric residue formation was investigated during multistep plasma etching of tungsten/TiN/Ti film using SF6 and Cl2 gas chemistries in the same reactor. Heavy polymeric residues were formed during TiN/Ti etching by the reaction of Ti and residual fluorine gases originating from previous SF6 plasma and seemed to be TiF

x

residues from the results of micro auger electron microscope (µ-AES) analysis and etch rate of polysilicon with residual gas-assisted Ar sputtering. It is highly recommended that multistep etching processes using different gas chemistries be carried out in separate reactors.
Growth of Epitaxial CeO2 Films on (1̄012) Sapphire by Halide Source Plasma Enhanced Chemical Vapor Deposition
Authors: Nakao Hiroshi , Yamawaki Hideki , Yoshida Chikako , Takauchi Hideki , Hirotaka Tamura Hirotaka Tamura , Naoki Yokoyama Naoki Yokoyama
Published: October 2002

We grew epitaxial CeO2 films on (1̄012) sapphire by halide source plasma enhanced chemical vapor deposition (halide-PECVD) using CeBr3 and O2 as source materials. We obtained amorphous films at substrate temperatures of 620° C, polycrystalline films at 680° C, and highly aligned films at 720°C. X-ray diffraction patterns show that (001) CeO2 is parallel to (1̄012) sapphire, and electron channeling patterns show [110] CeO2 aligned with [22̄01] sapphire. AFM shows very smooth films with a maximum variation of ± 2 nm. We grew YBCO film on CeO2/sapphire with a T
c of 83 K.
Unusual Dielectric Behavior of La–Ti–Al–O Ceramics with Perovskite Structure
Authors: Hideki Yoshioka Hideki Yoshioka
Published: October 2002

Perovskite compounds, La(2+
x
)/3(Ti1-
x

Al

x

)O3 with x ranging from 0.05 to 0.15, were prepared and the dielectric properties were investigated. Partial substitution of Al3+ for Ti4+ in La2/3TiO3 stabilizes the deficient perovskite structure with ordered A-site cation vacancy. Dielectric loss peaks show the existence of a relaxation process due to ionic motion related to the cation vacancy. High dielectric constants were obtained at lower frequency than the dielectric loss peak.
Direct Synthesis of Trans Polyacetylene Films with Conjugated System of Long Average Length and Narrow Distribution
Authors: Nishioka Takahiro , Suruga Kazuyuki , Ishikawa Ken , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: October 2002

A trans polyacetylene film was synthesized directly to reduce defects induced by ordinary thermoisomerization. Polymerization was carried out at high temperatures or by use of a different catalyst system. The films synthesized by both methods contain a larger amount of trans segments. From reflection spectra, they show a narrower peak at a lower energy than that observed in the ordinary thermoisomerized film. This implies that the films have conjugated systems of long average length and narrow distribution. A decrease in polymerization rate was found to be effective for the direct synthesis of such a trans polyacetylene film.
Prevention of Thermal Degradations by Using Dehydrated LiNbO3 Crystal
Authors: Koide Akira , Hajime Shimizu Hajime Shimizu , Toshihiko Saito Toshihiko Saito
Published: October 2002

Occurrence of the lithium outdiffusion phenomenon during thermal treatment in dry O2 is prevented by use of dehydrated LiNbO3 crystal. Microscopic and spectroscopic observations, as well as refractive index measurement showing a many advantages of this method are reported.
Nanofabrication with Langmuir-Blodgett Films of a Chemical Amplification Resist SAL601
Authors: Yoshimura Toshiyuki , Asai Naoko , Hiroshi Shiraishi Hiroshi Shiraishi , Shinji Okazaki Shinji Okazaki
Published: October 2002

Nanometer fabrication has been investigated with Langmuir-Blodgett (LB) films made of a chemical amplification resist SAL601 (Shipley Co.). It is found that uniform SAL601 LB films are formed by a conventional method, in which the surface pressure is reduced during film transfer. Finely focused electron beams are used for fabrication. Ultra small edge roughness in the delineated resist patterns (nano edge roughness) is suppressed by using LB technique compared to spin-coating, but sensitivity of the LB film is lowered. Suppression of the nano edge roughness in LB films is thought to be due to an ordered structure, which is indicated by Fourier transform infrared spectroscopy measurements.
Shrinkage Effect of Local Area of Polymer Film on Adhesion Behavior
Authors: Kawai Akira , Takata Hitoshi Nagata
Published: October 2002

We report a dependency of adhesion behavior in HF aqueous solution on film shrinkage of local area in a photoresist/silicon-oxide system. Micro window patterns of photoresist film are formed by means of photolithography. Side etching length of silicon-oxide substrate increases and saturates with the shrunken area of photoresist film. Adhesion strength can be expressed as a function of shrunken area.
Effects of N2O-Plasma Treatment of a-SiOxNy/a-SiNx Gate Insulators on Electrical Stability of a-Si:H Thin-Film Transistors
Authors: Jen Tean-Sen , Leu Shyue-Ter , Chou Tsung-Chih , Chang Jyh-Wong Hong
Published: October 2002

N2O-plasma was used to treat the as-deposited a-SiO

x

N

y

/ a-SiN

x

gate insulators of inverted-staggered a-Si:H thin-film transistors (TFTs), and its effects on electrical properties of TFTs were investigated. The TFTs with N2O-plasma-treated gate insulators tended to have a smaller threshold voltage (V
th), V
th shift and hysteresis width (W
FB) of the forward and backward transfer characteristics. In addition, the results of a bias-temperature stress (BTS) experiment showed that the N2O-plasma-treated devices had a smaller decay of drain current with time. These phenomena demonstrated that the N2O-plasma treatment could be used to improve the electrical stability of a-Si:H TFTs.
Optical Properties of ZnSe/ZnMgSSe Single Quantum Wells Grown by Metalorganic Molecular Beam Epitaxy
Authors: Jun Suda Jun Suda , Yoichi Kawakami Yoichi Kawakami , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: October 2002

In this letter we report optical properties of ZnSe/ZnMgSSe single quantum wells (SQWs) grown by metalorganic molecular beam epitaxy (MOMBE). At 4.2 K, a 10.5 monolayer (30 Å) ZnSe SQW confined in Zn0.90Mg0.10S0.18Se0.82 layers exhibited intense purplish blue photoluminescence (PL) peaking at 2.865 eV, whose linewidth was as small as 5 meV. This emission was assigned to the n=1 heavy-hole exciton (E
x1hh). Another peak appeared on the low-energy side of E
x1hh under high excitation and grew nonlinearly with increasing excitation intensity. We tentatively attribute this line to the recombination of biexcitons. The exciton-longitudinal-optical(LO)-phonon coupling constant was also assessed from the temperature dependence of PL measurements.
A Model-Based Comparison of the Performance of AlGaAs/GaAs and Si/SiGe Heterojunction Bipolar Transistors (HBTs) Including Thermal Effects
Authors: J. J. Liou J. J. Liou
Published: October 2002

The performances of AlGaAs/GaAs and Si/SiGe heterojunction bipolar transistors (HBTs) at room temperature are compared based on an analytical model which includes relevant physics such as the high-current and thermal (or self-heating) effects. Three figures of merit of the HBTs are calculated and compared: the dc current gain, cutoff frequency, and maximum oscillation frequency. Our results indicate that the AlGaAs/GaAs HBT possesses less uniform but higher peak current gain, cutoff frequency, and maximum oscillation frequency than its Si/SiGe counterpart. Furthermore, at high current densities, it has been shown that the thermal effect becomes important and degrades the performance of AlGaAs/GaAs HBT more significantly than that of Si/SiGe HBT due primarily to the poorer GaAs thermal conductivity than Si.
Emitter Material Comparison between InGaP and InGaAsP in GaAs-Based Heterojunction Bipolar Transistors
Authors: Ohkubo Michio , Iketani Akira , Masakiyo Ikeda Masakiyo Ikeda , Takao Ninomiya Takao Ninomiya
Published: October 2002

In0.49Ga0.51P ( E

g
=1.87 eV)/GaAs and In0.38Ga0.62As0.22P0.78 ( E

g
=1.77 eV)/GaAs Npn heterojunction bipolar transistors (HBTs) were fabricated. In devices with 110 µm×110 µm emitter areas, the curtent gains of both devices were the same value of 14 at a collector current density of 700 A/cm2. By contrast, the turn-on voltage of InGaAsP/GaAs HBTs was 0.01 V smaller than that of InGaP/GaAs HBTs, which indicated that the conduction band discontinuity of the InGaP/InGaAsP heterojunction was much smaller than the valence band discontinuity.
Metal Semiconductor Metal Photodetectors and Modulators for Long Wavelength Applications: Optimization of Solid Source Molecular Beam Epitaxy of AlInAs/(Al)GaInAs-Heterostructures
Authors: Kummetz Thomas , Dirr Siegfried , Sickmöller Markus , Herrmann Annegret , Wolfgang Kowalsky Wolfgang Kowalsky
Published: October 2002

Solid source molecular beam epitaxial (MBE) growth of AlInAs/(Al)GaInAs heterostructures for applications in metal-semiconductor-metal (MSM) photodetectors and electrooptic MSM modulators has been optimized with regard to high frequency performance. The influence of the thickness of an AlInAs barrier enhancement layer on the dynamical characteristics is also investigated. In contrast to the commonly chosen thickness of about 10 nm we show that an increase to 100 nm AlInAs results in bandwidth enhancement and noise reduction. Using these improved structures with breakdown voltages exceeding V
B=100 V for electrooptic switching we attain an on-off-ratio of 19:1.
Simple and Stable Single-Electron Logic Utilizing Tunnel-Junction Load
Authors: Hironobu Fukui Hironobu Fukui , Minoru Fujishima Minoru Fujishima , Koichiro Hoh Koichiro Hoh
Published: October 2002

Novel tunnel-junction-load single-electron logic (SEL) was proposed, which is simpler than the complementary SEL and its output is more stable than that of the resistance-load SEL. We analyzed the static operation of a tunnel-junction-load inverter by examining the map of stability domains and the dynamic operation using the Monte Carlo simulation. As a result, it was found that the tunnel-junction SEL has sufficient gain when the temperature is under 4 mK, and operates properly even when two inverters having the same parameters are serially connected.
Physical Mechanism of Chaos in Thyristors and Coupled-Transistor Structures
Authors: Takahiro Irita Takahiro Irita , Tatsuo Tsujita Tatsuo Tsujita , Minoru Fujishima Minoru Fujishima , Koichiro Hoh Koichiro Hoh
Published: October 2002

Electronic chaos in thyristors was observed by ac signal excitation of the anode of thyristors. The origin of this chaotic phenomenon was revealed by detailed measurement of the p-base potential, measurement with a coupled-transistor structure and the results of SPICE simulation. Chaos was generated by the return-mapping nature in the variation of the p-base potential. Chaotic behavior in a thyristor was also reproduced in the experimental coupled-transistor structure and in the results of SPICE simulation.
Effect of Hydrogen Plasma Treatment on n-InP Surfaces
Authors: Yoshifumi Sakamoto Yoshifumi Sakamoto , Takashi Sugino Takashi Sugino , Hideaki Ninomiya Hideaki Ninomiya , Koichiro Matsuda Koichiro Matsuda , Junji Shirafuji Junji Shirafuji
Published: October 2002

Surfaces of n-InP treated with remote hydrogen plasma have been analyzed in terms of X-ray photoelectron spectroscopy (XPS), Kelvin probe, current-voltage characteristics of Schottky barrier junctions and isothermal capacitance transient spectroscopy (ICTS). It is confirmed by XPS analysis that the native oxide is removed from the InP surface by the \H2-plasma treatment. Schottky junctions formed byin situevaporation of various metals immediately after the remote \H2-plasma exposure show that the barrier height is pinned at about 0.5 eV, irrespective of Schottky metal. This value is somewhat higher than the barrier height of 0.4 eV for untreated surfaces. It is observed by Kelvin probe measurement that the Fermi level shifts to an energy around 0.53 eV below the conduction band edge upon \H2-plasma treatment from 0.39 eV for an untreated surface. Furthermore, a deep trap level with the activation energy of 0.51 eV below the conduction band edge was detected for samples treated with \H2 plasma by ICTS measurement. The pinned behavior of the Schottky barrier height is speculated to be related to the trap level generated by \H2-plasma treatment.
Effect of Annealing on Photoluminescence Spectra and Film Structure in a-SiNx:H
Authors: Kazuki Wakita Kazuki Wakita , Shinji Makimura Shinji Makimura , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

The change of photoluminescence (PL) spectra and structure in hydrogenated amorphous silicon-nitrogen alloy films deposited by glow-discharge decomposition of SiH4 and NH3 with various mixture ratios has been investigated as a function of annealing temperature. The PL spectra have a single broad band in the visible range and its peak energy shifts toward lower energy for NH3/SiH4≤6.0 and higher energy for NH3/SiH4≥6.8 by annealing at 600°C. The PL-peak energy varies linearly with optical band gap. Annealing at temperatures higher than 400°C breaks Si–H and N–H bonds to form Si–N bonds for all samples. The Si–Si bond concentration decreases with annealing for NH3/SiH4≥7.5, while it is considered to increase for NH3/SiH4=5. The change observed in the PL-peak energy and the optical band gap with annealing is associated with the variation in the concentration not only of Si–N but also of Si–Si bonds.
Relationship between Low-Noise Performance and Electron Confinement in the Channel of Two-Mode Channel Field-Effect Transistors in a Low-Drain-Current Condition
Authors: Sawada Minoru , Matsumura Kohji , Inoue Daijiro , Nakamoto Hiroyuki , Yasoo Harada Yasoo Harada
Published: October 2002

We investigated the relationship between the minimum noise figure (N
F
min) and electron confinement in the channel of the two-mode channel field-effect transistor (TMT) which we developed previously, by comparing the TMT and an AlGaAs/InGaAs pseudomorphic high electron mobility transistor (P-HEMT) with a 10 nm InGaAs channel layer. The TMT had a superior measured N
F
min and stronger electron confinement in a low-drain-current (I
ds) bias condition than the P-HEMT. The superior measured N
F
min of the TMT resulted in a smaller fitting factor (K
f) in Fukui's noise equation than that of the P-HEMT. We demonstrated that the stronger electron confinement of the TMT leads to an increase in the correlation coefficient between drain noise current and gate-induced noise current and results in a smaller K
f, which plays an important role in the reduction of N
F
min.