bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Characterization of AlP/GaP Disordered Superlattice by Dynamical Simulation of X-Ray Diffraction
Authors: Wang Xue-Lun , Akihiro Wakahara Akihiro Wakahara , Akio Sasaki Akio Sasaki
Published: October 2002

Dynamical simulation of X-ray diffraction is used to characterize structural
properties of (AlP)

m

/(GaP)

n

(m, n=h, k, l) disordered superlattices (d-SLs).
Many small diffraction peaks appear around the main peak, and peak intensities become
weaker as the deviation from the average thickness increases. The observed diffraction
patterns can be interpreted if the repetition of random series in the superlattice is
taken into account. It is found that the total number of monolayers (MLs) of the 6
constituent layers or the average number of MLs of a d-SL can be precisely determined
from the smallest peak separation or the angular distance between the main peak and the 0th-order diffraction peak.
Significance of Charge Sharing in Causing Threshold Voltage Roll-Off in Highly Doped 0.1-µ m Si Metal Oxide Semiconductor Field Effect Transistors and its Suppression by Atomic Layer Doping
Authors: Noda Hiromasa , Kaori Nakamura Kaori Nakamura , Shin'ichiro Kimura Shin'ichiro Kimura
Published: October 2002

An investigation into the influence of substrate doping concentration on the short channel effects in 0.1-µm nMOSFETs (n-channel metal oxide semiconductor field effect transistors) has shown that, when substrate dopant concentration is higher than 1×1018 cm-3, threshold voltage (V
th) roll-off is not improved by heavier doping in the substrate, although punchthrough is suppressed. Furthermore, it was found that threshold voltage roll-off is characterized by a reduction in subthreshold swing. Experimental results suggest that the threshold voltage roll-off is heavily influenced by the effect of the two-dimensional shape of the drain depletion region, namely the charge sharing mechanism. As a candidate device for suppressing charge sharing, the ALD (atomic-layer doped) MOSFET was considered. Its excellent scalability was demonstrated by device simulation.
Silicon Wafer Direct Bonding without Hydrophilic Native Oxides
Authors: Himi Hiroaki , Matsui Masaki , Seiji Fujino Seiji Fujino , Tadashi Hattori Tadashi Hattori
Published: October 2002

Silicon wafer direct bonding was accomplished between two surfaces which had no hydrophilic native oxide layers. Prior to bonding, two wafers were dipped in conc-HF solution ( ∼49% aq.) to remove the native oxide layers and then immersed in deionized water. The level of bonding was evaluated by X-ray topography, high resolution transmission electron microscopy (HRTEM) and tensile strength measurement. It was found that the bonded wafer pairs were void-free and had good bonding strength. HRTEM observation showed that the crystal lattice was continuous and had only small distortions and precipitates. Spreading resistance (SR) measurement across the interface showed that the electric resistance did not increase at the bonding interface. It is suggested that the OH groups which substitute the F atoms terminated on the small portion of the surface play an important role in this conc-HF-treated bonding.
Methodology for Accurate Oxygen Distribution Analysis and Its Application to YBa2Cu3Ox Thin Films Using 16O(α, α)16O 3.045 MeV Resonance Reaction
Authors: Watamori Michio , Fumiya Shoji Fumiya Shoji , Kenjiro Oura Kenjiro Oura
Published: October 2002

The enhancement factor of oxygen of 16O(α, α)16O resonance
for a Rutherford backscattering cross section has been investigated using SiO2
films of various thicknesses. A new procedure to accurately extract the resonant oxygen
height from a raw spectrum has been proposed. With this procedure, the dependence
between the film thicknesses and resonant signals has been investigated, and was
found to agree well with a computer simulation within experimental error. Using the
enhancement factor, the depth dependence of oxygen concentration in the YBa2Cu3O

x

/MgO
systems has been estimated accurately. Estimations of the accuracy of elastic backscattering analysis are also given.
Hydrogen-Sensitive Property of Switching Device with a Pd–Si Tunnel Metal Insulator Semiconductor Structure
Authors: Shinji Nakagomi Shinji Nakagomi , Tatsuo Yamamoto Tatsuo Yamamoto
Published: October 2002

The effect of atmosphere on the switching device with a Pd–Si tunnel metal insulator semiconductor (MIS)
structure is studied. The MIS device with the Pd-insulator-(n)Si-(p
+)Si structure reveals a negative-resistance
switching property. In addition, the threshold voltage of switching is sensitive to hydrogen gas concentration. The
current-voltage characteristics of the MISS device were measured for various conditions of gases in detail, with
particular attention on the effect of oxygen. We can obtain information on work function by measuring the
capacitance-voltage characteristics and the temperature dependence of the current in the “off-state” region.
The variation of the work function with change of atmosphere was confirmed for the switching device with the Pd–Si
tunnel MIS structure, for the first time.
The Effects of Space-Charge-Layer Thickness Modulation on Diffusion Capacitance
Authors: Juin J. Liou Juin J. Liou , Adelmo Ortiz-Conde Adelmo Ortiz-Conde
Published: October 2002

The effect of junction space-charge-layer thickness modulation is normally omitted in the conventional diffusion
capacitance model. This note calculates the diffusion capacitance including such an effect and investigates the errors
introduced by the conventional model under a wide range of bias conditions, as well as for different doping
concentrations, different layer thicknesses, and different temperatures.
Defects in Heavily Phosphorus-Doped Si Epitaxial Films Probed by Monoenergetic Positron Beams
Authors: Uedono Akira , Tanigawa Shoichiro , Suzuki Ryoichi , Ohgaki Hideaki , Mikado Tomohisa
Published: October 2002

Vacancy-type defects in heavily phosphorus-doped Si epitaxial films were probed by monoenergetic positron beams.
Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured for the
epitaxial films grown on the Si substrates by plasma chemical vapor deposition. For the as-deposited film,
divacancy-phosphorus complexes were found with high concentration. After 600° C annealing, vacancy
clusters were formed near the Si/Si interface, while no drastic change in the depth distribution of the
divacancy-phosphorus complexes was observed. By 900° C annealing, the vacancy clusters were annealed
out; however, the average number of phosphorus atoms coupled with divacancies increased. The relationship between the
vacancy-type defects probed by the positron annihilation technique and the carrier concentration was confirmed.
Deposition and Characterization of Ferroelectric Pb[(Mg1/3Nb2/3)xTi1-x]O3 Thin Films by RF Magnetron Sputtering
Authors: Jiang Ming-Chrong , Tian-Jue Hong Tian-Jue Hong , Tai-Bor Wu Tai-Bor Wu
Published: October 2002

Ferroelectric Pb[(Mg1/3Nb2/3)

x

Ti1-
x

]O3 (PMNT) thin films with a well-developed
perovskite structure were prepared on Si(100) and Pt/Ti/ SiO2/Si(100) substrates by rf magnetron sputtering
deposition at high substrate temperatures of 480–650° C. The effect of substrate materials was
investigated by X-ray diffraction analysis. The substrates that were topped with a Pt/Ti electrode exhibited a
significant effect on reducing the perovskite phase formation temperature of PMNT films; in addition, the TiO2
rutile phase was found to be formed at the interface between the PMNT film and Pt electrode. It was discovered that
the TiO2 rutile phase would degrade the dielectric and ferroelectric properties of the PMNT films. The
0.5-µm-thick perovskite PMNT films of x=0.3–0.5 exhibited a high dielectric constant
(k) of 1000–1300, and a dissipation factor less than 0.04 at 1 kHz. Moreover, the films showed satisfactory
ferroelectric characteristics. The remanent polarization (P
r) or coercive field (E
c) ranged from
23.5 µ C/cm2 and 82.5 kV/cm, respectively, for 10 PMNT (x=0.1) to 10.2 µ C/cm2 and
49 kV/cm for 50 PMNT (x=0.5) thin films. Due to the formation of a relatively thick TiO2 interface layer
at a high deposition temperature, the 70 PMNT (x=0.7) films did not show satisfactory dielectric or ferroelectric
properties. However, by adding 3 mol% La on the PMNT to reduce the perovskite formation temperature, a
0.5-µm-thick Pb0.97La0.03Mg0.235Nb0.44Ti0.325O3 (PLMNT) film was
prepared on the Pt/Ti/ SiO2/Si substrate, and results of P
r=8.5 µ C/cm2,
E
c=46 kV/cm with k=1220 and tan
δ<0.04 were obtained.
Patterning of 2–10 Nanometer-Scale Plasma-Polymerized Organic Films by Atomic Force Microscope
Authors: Vinogradov Georgy K. , Gorwadkar Sucheta , Kenji Senda Kenji Senda , Shinzo Morita Shinzo Morita
Published: October 2002

Ultrathin films of 2–10 nm thickness were deposited by pulsed discharge plasma polymerization. The film
surface topography was studied by an atomic force microscope (AFM), which showed that the films are smooth and
pinhole-free. The AFM was used to produce nanometer-scale indentations/holes in these deposited ultrathin organic
films. The patterning process is governed by several factors: mechanical and Coulomb forces, heat effects, material
transfer, and electric charge deposition depending on the conditions. The patterning results indicate the AFM can be
used for the formation of nanometer-scale structures.
Microstructure and Crystallinity of N-Type Porous Silicon
Authors: Takemoto Kuniko , Yoshio Nakamura Yoshio Nakamura , Osamu Nittono Osamu Nittono
Published: October 2002

Microstructure and crystallinity of a porous silicon (PS) layer formed on a highly doped n-type silicon substrate
were examined in detail, and the luminescent nature of the PS layer was also studied qualitatively. A layered
pore structure developed after about 3000 s of anodization, and pore morphology became simpler with increasing
thickness of the PS layer. All luminescent PS layers were found to show spongelike structure near the surface.
From the peak width of X-ray rocking curves, the crystallinity of n-type PS was found to be inferior to that
of p-type PS. No systemic tendency of the lattice expansion was seen under various forming current densities.
Luminescent PS layers showed slightly broader background intensity than nonluminescent ones. It was also
shown that the anodization of the PS layer took place through two anodization processes: primary and secondary
anodizations; secondary anodization was effective in forming luminescent parts having spongelike structure.
Preparation of Tl-System Superconducting Thin Films by the Mist Microwave-Plasma Chemical Vapor Deposition Method
Authors: Takahashi Naoyuki , Akinori Koukitu Akinori Koukitu , Hisashi Seki Hisashi Seki
Published: October 2002

Superconducting thin films of Tl–Sr–Ca–Cu–O were prepared on single-crystal MgO(100)
substrates by the mist microwave-plasma chemical vapor deposition method, and the dependence of
T
c-zero of films on the input molar ratio of oxygen
O
R
=F
O
2
/(F
O
2
+total F
A
r
) was investigated. In addition, the effect
of the Bi addition on Tl–Sr–Ca–Cu–O superconducting thin films was studied. The
prepared films were constituted of the 1212 and/or 1223 phases with c-axis
orientation perpendicular to the substrates. The maximum T
c-zero
(zero resistance; 102 K) of as-deposited films was obtained at the input molar ratio of oxygen
( O
R
) of 0.30, the microwave power of 300 W and the addition amount (x= Bi/(Tl+Bi)) of 0.30.
Characteristics of Thin-Film Transistors Fabricated on Nucleation-Controlled Poly-Si Films by Surface Steps
Authors: Asano Tanemasa , Kenji Makihira Kenji Makihira , Hiroomi Tsutae Hiroomi Tsutae
Published: October 2002

Polycrystalline Si films were prepared on SiO2/Si substrates by solid-phase crystallization of vacuum-evaporated amorphous Si with a nucleation-controlled process by steps formed at the substrate surface. Crystallinity of the Si films and characteristics of n- and p-channel thin-film transistors fabricated on the Si films have been investigated. The Si films were found to be composed of stripe-shaped grains elongated in the direction perpendicular to the step. The vast majority of the grains had the <111> axis in the direction perpendicular to the substrate surface. Concerning the in-plane crystal orientation, a tendency for the <211> axis to align in the direction perpendicular to the step was found. Both n- and p-channel transistors fabricated on the Si films showed improved channel carrier mobility compared to those fabricated on Si films prepared by solid-phase crystallization without nucleation control. The improvement was more pronounced in n-channel transistors, which suggested that p-channel transistor performances were less sensitive to grain boundaries.
The Effect of Amorphous Layer at NiCr/Ni Silicide Interface on the Sheet Resistivity of Ni Silicides
Authors: Ju-Hyeon Lee Ju-Hyeon Lee
Published: October 2002

Two sets of samples with different interfacial amorphous layers were prepared:
one with Pt impurity (Pt process) and the other without Pt impurity (Pt-free process)
at NiCr/Si interfaces. Following annealing, Cr-rich amorphous layers (a-layers) with
and without Pt impurity formed at NiCr/Ni silicide interfaces, respectively. These
a-layers control the formation and the growth of Ni silicides. The Pt impurity seems
to move with the a-layers and suppress the growth of the a-layers. The a-layers without
Pt impurity are therefore thicker and thermally more stable. The thicker a-layers
result in larger silicide grains and more uniform silicide layers. Thus, Ni silicides
with low sheet resistivity can be obtained by this Pt-free process.
Characterization and Modification of Amorphous Carbon Films Consisting of sp2 and sp3 Bonds Using Magneto-Plasma Dynamic Arc-Jet
Authors: Tanabe Yasuhiro , Burkhard Günther , Ishikura Takebumi , Tsunoda Katsunori , Hasuo Hiroto , Tamaru Masanari , Tamura Hideki , Uematsu Akira Sawaoka
Published: October 2002

A magneto plasma dynamic arc-jet (MPD arc-jet) can introduce a large energy pulse
to a source gas and enable synthesis amorphous carbon films consisting of sp2 and
sp3 bonds (hybrid amorphous carbon). The process conditions which affect the
structure and the properties of the synthesized films are described here. Homogeneous
films were obtained using the MPD arc-jet technique. Films were also in-situ
modified with modifier gases due to the excellent characteristics of the MPD arc-jet.
A substrate temperature of 200°C and a bias potential of -200 V resulted
in harder films. The hardness are related to the hydrogen content and chemical bond
nature of the carbon in the films. Homogeneity in the deposition direction could be
achieved by in-situ modification. The refractive index, hardness, and other
properties of the films were controlled by this modification.
The Application of Deep UV Phase Shifted-Single Layer Halftone Reticles to 256 Mbit Dynamic Random Access Memory Cell Patterns
Authors: Hashimoto Kohji , Samuels Donald J. , Farrell Timothy R. , Moy Dan , Martino Ronald M. , Ferguson Richard A. , Maurer Takashi Sato
Published: October 2002

We have applied deep UV (DUV) halftone reticles, with a single layer absorptive
shifter consisting of silicon nitride, to 256 Mbit dynamic random access memory (DRAM)
critical levels, and have evaluated the resolution in those cell patterns. For the
periodic line levels, halftone reticles were combined with off-axis illumination (OAI)
techniques. Resolution capabilities were characterized not only with stepper exposures
but also with direct aerial image measurement. For hole levels such the Storage Node
and Bitline Contact, halftone reticles offered clear improvement with standard illumination
as compared to conventional reticles. For line levels such the Isolation, Wordline
and Bitline, dramatic improvement was obtained with the combination of halftone reticles and off-axis illumination.
Sub 20 nm Stitching and Overlay for Nano Lithography Applications
Authors: Koek Bartholomeus H. , Chisholm Thomas , Romijn Johannes , van Run Arnoldus J.
Published: October 2002

The typical placement, stitching and overlay performance of high resolution electron
beam lithography systems is not compatible with the minimum linewidth which can be achieved.
Linewidths of 20 nm or less can be obtained, but placement accuracy is typically 3 times higher.
The major components in the error distribution of the stitching and overlay performance of
the Leica EBPG-5FE have been analysed and indicate that the number of stage movements and
stage reproducibility are the predominant factors in the error budget. A direct write
algorithm has been developed which reduces the influence of the stage. The calculated
3σ stitching and overlay errors for this new algorithm are 14 nm. Experimental
results showed 8 nm stitching and 10 nm overlay (3σ), obtained in a 546 µ m field.
Nanolithography Using a Chemically Amplified Negative Resist by Electron Beam Exposure
Authors: Manako Shoko , Ochiai Yukinori , Fujita Jun-ichi , Samoto Norihiko , Shinji Matsui Shinji Matsui
Published: October 2002

We study the resolution limit for dot patterns using a chemically amplified negative
resist by the nanometer electron beam lithography system. It is confirmed that the
substrates baked at 270° C after HMDS coating are suitable for fine resist
dot patterning. In addition, the post exposure bake (PEB) dependencies of sensitivity
and resolution are investigated. As a result, 20-nm-diameter dot resist patterns with a
30 nm height, and 35-nm-diameter dot resist patterns with a 50 nm height are fabricated on Si substrates.
Focused Ion Beam Lithography Using Ladder Silicone Spin-On Glass
Authors: Suzuki Kohei , Yamashita Motoji , Hirokazu Ueda Hirokazu Ueda , Akimitsu Nakaue Akimitsu Nakaue
Published: October 2002

Ladder silicone spin-on glass (LS-SOG) has been used in focused ion beam (FIB)
lithography as the negative resist. LS-SOG has shown excellent stability and resolution.
The 110 nm pattern consisting of silicon oxide has been delineated with a FIB dose of 1.2 µ C/cm2.
This lithographic technique has been applied to polysilicon etching and the bilevel
resist process. The 100 nm lines of polysilicon and the bilevel resist patterns were
fabricated with FIB doses of 1.2 µ C/cm2 and 10 µ C/cm2, respectively.
Characterization and Application of Materials Grown by Electron-Beam-Induced Deposition
Authors: Koops Hans W. P. , Kretz Johannes , Rudolph Michael , Weber Markus , Lee Gerold Dahm
Published: October 2002

Electron-beam-induced deposition of materials has been known for almost 40 years from contamination writing. It has developed into “additive lithography” with nanometer resolution employed in scanning electron microscopes, in dedicated lithography systems, in reducing image projection systems, and in scanning tunneling microscopes. The technique allows deposition of nanometer- to micrometer-size structures with nanometer precision in three dimensions without supplementary process steps such as lift-off or etching procedures. Depending on the deposition conditions, novel compound materials are created from organometallic precursors which form resistors with a resistivity ranging from 103Ω· cm to 2×10-3Ω· cm and sustain current densities higher than 5×105A/cm2without damage. High-resolution transmission electron microscope analysis of the deposits reveals a new class of nanocrystalline compound materials. Crystals of metals or metalcarbides and oxides are immersed in a matrix of carbonaceous material. The deposition process is compatible with conventional VLSI technology. Tips for atomic force and scanning tunneling microscopy can be produced with radii of curvature as small as 5 nm. Field electron emission is obtained from deposited tips starting at an extraction voltage of 8 V and yielding 180 µ A of current at 20 V. Three-dimensional conducting structures can be produced as sensors.
Laser Surface Cleaning in Air: Mechanisms and Applications
Authors: Lu Yong-Feng , Aoyagi Yoshinobu , Takai Mikio , Namba Susumu
Published: October 2002

Surface contaminations are removed by laser irradiation with pulse output and short wavelength in ambient air.
It is a dry cleaning process to remove surface contaminations without using ultrasonic cleaning requiring carbon
fluorochloride and other organic solvents. The mechanisms of laser cleaning may include laser photodecomposition,
laser ablation and surface vibration due to the impact of the laser pulse. Examples of cleaning metal surfaces and magnetic head sliders show that this cleaning process could be widely used in various industrial applications.
Recent Progress in Micromachining and Applications to Microactuators
Authors: Hiroyuki Fujita Hiroyuki Fujita
Published: October 2002

The successful fabrication and operation of microactuators and micromechanical parts
by IC-based micromachining technology has provided the opportunity to produce microelectromechanical
systems (MEMS) or micromachines. This paper deals with the recent progress in micromachining
processes and microactuators fabricated by them. A system architecture suitable for MEMS
and applications of MEMS are also discussed.
GaAs/AlGaAs Quantum Wells Grown by Low-Temperature Molecular Beam Epitaxy with Atomic Hydrogen Irradiation
Authors: Okada Yoshitaka , Ohta Shigeru , Tomoya Fujita Tomoya Fujita , Mitsuo Kawabe Mitsuo Kawabe
Published: October 2002

Optical properties of GaAs/AlGaAs quantum wells grown by molecular beam epitaxy with atomic hydrogen irradiation have been investigated by photoluminescence (PL) method. Narrow PL linewidths have been obtained for samples grown at a low-temperature of 330° C with atomic hydrogen and without any growth interruptions. This is due to enhanced Ga migration on GaAs (100) surface under the presence of atomic hydrogen thereby resulting in atomically smooth interfaces. It has also been shown that the PL intensities can be improved as the non-radiative recombination centers could be effectively passivated by the hydrogen atoms.
Composition Modulation of InxGa1-xAs Quantum Wells by Fast Dimer Arsenic Flux Change Using Valved Arsenic Cracker
Authors: Liu Der-Cherng , Lee Chien-Ping , Tsai Kuang-Lung , Jian-Shihn Tsang Jian-Shihn Tsang , Horng-Rung Chen Horng-Rung Chen
Published: October 2002

By fast change of the As2 flux using a high temperature valved cracker, we have demonstrated the growth of strained In

x

Ga1-
x

As quantum wells with different compositions. The modulation of composition is due to the change in incorporation rates of the group III atoms under different As2 fluxes. Photoluminescence (PL) emission from the quantum wells clearly indicates the change in composition. A change of In composition from 20.6% to 8.5%, has been achieved by changing the V/III beam-equivalent-pressure (BEP) ratio from 11.7 to 3.9. By this technique of composition modulation, we have fabricated strained In

x

Ga1-
x

As/GaAs single quantum well lasers with different emission wavelengths.
Heterostructures of Crystalline Organic and Inorganic Semiconductors for Applications in Optoelectronic Integrated Circuits
Authors: Rompf Christoph , Bernd Hilmer Bernd Hilmer , Wolfgang Kowalsky Wolfgang Kowalsky
Published: October 2002

Heterostructures of crystalline organic and inorganic semiconductors based on the aromatic compound PTCDA (3, 4, 9, 10-perylenetetracarboxylic dianhydride, C24O6H8) are investigated. Crystal growth by organic molecular beam deposition (OMBD) on different substrates and optical characterization are discussed. Homogeneous crystalline films are attained at low growth rates and substrate temperatures from T=77 K to T=350 K. With regard to applications in optoelectronic integrated circuits (OEICs) waveguide structures, photodetectors and a concept for the integration of these two devices are presented. Due to the low process temperatures optoelectronic devices can be prepared on already processed III-V and silicon wafers.
Surface-Emitting Laser with a Common-Anode Configuration for Application to the Photonic Parallel Memory
Authors: Adachi Hideto , Kobayashi Yasuhiro , Toyoji Chino Toyoji Chino , Kenichi Matsuda Kenichi Matsuda
Published: October 2002

A novel structure of a vertical-cavity surface-emitting laser (VCSEL) was proposed and demonstrated. Using a common-anode configuration, lower mesa height and lower electrical resistance were realized. The threshold current was 6 mA for a 10-µm-diameter device under room-temperature pulsed operation. The lasing wavelength was 939 nm. This configuration is suitable for large-scale integration. We also propose an optoelectronic integrated circuit (OEIC) with the common-anode configuration, which consists of a VCSEL and a heterostructure phototransistor (HPT) for optical parallel processing.
New RAM-bus Memory System with Interchip Optical Interconnection
Authors: Miyake Kouji , Tanaka Tsuyoshi , Etoh Takeshi , Tsuno Morikazu , Shin Yokoyama Shin Yokoyama , Mitsumasa Koyanagi Mitsumasa Koyanagi
Published: October 2002

A new optical RAM-bus (ORAM-bus) memory system has been proposed. The ORAM-bus memory has a number of optical interconnections to connect many memory chips. Data transfer using the guided optical interconnections is performed through the optical coupling flip-flop (OC-FF) circuit of the optical coupling sense amplifiers. The ORAM-bus memory test chips were fabricated using 2 µm complementary metal-oxide-semiconductor (CMOS) technology. The light-emitting diodes (LEDs) were successfully bonded onto the silicon test chips using the newly developed microbonding technology. The optical writing operation for ORAM-bus memory was demonstrated using the test chip.
Photoluminescence Dark Spot Dynamics in GaAs Grown on Si
Authors: Wada Naoki , Shiro Sakai Shiro Sakai , Masuo Fukui Masuo Fukui
Published: October 2002

It was found that DSs (dark spots) observed in room temperature PLI (photoluminescence images) of GaAs grown on Si substrates moved under certain conditions. The DS dynamics in planar GaAs on Si, UCGAS (undercut GaAs on Si), undercut structures on GaAs substrates and planar homoepitaxial GaAs are measured and compared. The number of moving DSs is larger and their speed is higher in the samples with higher stress and at higher excitation. The results are consistent with the dislocation dynamics in GaAs normally seen at elevated temperature.
Very Long Wavelength Intersubband Infrared Hot Electron Transistor
Authors: Gunapala Sarath D. , Liu John K. , True L. Lin True L. Lin , Jin S. Park Jin S. Park
Published: October 2002

We have demonstrated the first very long wavelength ( 16 µm) infrared hot electron transistor (IHET). This device utilizes a bound to continuum GaAs/Al

x

Ga1-
x

As (x=0.11) quantum well infrared photodetector (QWIP) as a photosensitive emitter, a wide quantum well as a base, and a thick Al

x

Ga1-
x

As (x=0.11) barrier between the base and the collector as an energy discriminating filter. This energy filter blocks the lower energy tunneled electrons, which drain through the base while higher energy photo electrons pass to the collector. Therefore, the detectivity of the device at the collector is much higher than the detectivity at the emitter.
Prediction of Spin-Polarization Effects in Quantum Wire Transport
Authors: Fasol Gerhard , Sakaki Hiroyuki
Published: October 2002

We predict a new effect for transport in quantum wires: spontaneous spin polarization. Most work on transport in mesoscopic devices has assumed a model of non interacting, spin-free electrons. We introduce spin, electron pair scattering and microscopic crystal properties into the design of mesoscopic devices. The new spin polarization effect results from the fact that in a single mode quantum wire, electron and hole bands still have two spin subbands. In general, these two spin subbands are expected to be split even in zero magnetic field. At sufficiently low temperatures the electron pair scattering rates for one spin subband ( e.g., the spin-down) can be much larger than for the other spin subband. This effect can be used for an active spin polarizer device: hot electrons in one subband ( e.g., `spin up') pass with weak pair scattering, while electrons in the opposite subband ( e.g., `spin down'), have high probability of scattering into the `spin-up' subband, resulting in spin polarization of a hot electron beam.
Surface Recombination Velocity in p-Type GaAs
Authors: Hiroshi Ito Hiroshi Ito , Tadao Ishibashi Tadao Ishibashi
Published: October 2002

Sufface recombination velocity in p-type GaAs is characterized by using a method which combines minority electron lifetime and photoluminescence measurements. Surface recombination velocities for samples with hole concentrations of 1017 cm-3 and 1018 cm-3 were 4.2×106 cm/s and 7.7×106 cm/s respectively, which are larger than the previously reported results for n-type GaAs. This difference is attributed to the difference in the thermal velocities between minority electrons and minority holes.
Optical Properties of an InGaAlAs/InP Type-II Superlattice
Authors: Hideki Kobayashi Hideki Kobayashi , Yuichi Kawamura Yuichi Kawamura , Hidetoshi Iwamura Hidetoshi Iwamura
Published: October 2002

Optical properties of an InGaAlAs/InP type-II superlattice are studied. Electroluminescence, transmissivity, photocurrent, and electroabsorption in the superlattice are measured at room temperature. The results are compared to those in bulk InP. The superlattice shows electroabsorption at around 1.1 µm, where linear absorption is small and a luminescence peak appears. An excitonic structure in the type-II superlattice is observed in photocurrent and electroabsorption spectra.
Feasibility of 1.55 µ m Intersubband Photonic Devices Using InGaAs/AlAs Pseudomorphic Quantum Well Structures
Authors: Hirayama Yuzo , Smet Jurgen H. , Peng Lung-Han , Clifton G. Fonstad Clifton G. Fonstad , Erich P. Ippen Erich P. Ippen
Published: October 2002

We propose to use 1.55 µm intersubband transitions as a key mechanism for novel photonic devices such as fast photonic switches which are applicable to current optical communication systems. The calculation of carrier relaxation times shows a few picosecond switching time for 1.55 µm intersubband transitions. The well-width dependence of intersubband transition energies in InGaAs/AlAs pseudomorphic quantum well structures has been studied to realize 1.55 µm intersubband transitions.
Selective Growth of Wire Structures of GaAs on CaF2 Using Focused Electron Beams
Authors: Kawasaki Koji , Kazuo Tsutsui Kazuo Tsutsui , Seijiro Furukawa Seijiro Furukawa
Published: October 2002

A selective growth method using the surface modification effect on a fluoride surface by electron beam exposure was investigated as a new microfabrication technique. Wire structures of GaAs on CaF2 with 500 nm width were obtained using a 40 keV electron beam at a dose of 2 µC/cm. The size of these structures was dependent on the dose and energy of the electron beam and thickness of the As film covering the surface of CaF2. From these experimental results and Monte Carlo simulation of injected electrons, it was found that the linewidths of structures were mainly determined by the forward scattering of electrons in the As film. The possibility of obtaining smaller size GaAs using higher energy electron beam and thinner As film is discussed.
Formation of Oxide-Free Nearly Ideal Pt/GaAs Schottky Barriers by Novel In Situ Photopulse–Assisted Electrochemical Process
Authors: Wu Nan-Jian , Hashizume Tamotsu , Hasegawa Hideki
Published: October 2002

An oxide-free Pt/GaAs Schottky barrier was fabricated by a novel i
n
s
i
t
u photopulse-assisted electrochemical process. Nearly ideal thermionic emission characteristics of a high barrier height φ Bn of 1.07 eV and an ideality factor of n=1.05, were observed over a range of 7 orders of magnitude of electric current. The results of atomic force microscopy (AFM), X-ray photoemission spectroscopy (XPS) and deep level transient spectroscopy (DLTS) measurements indicated that the novel electrochemical process produces a smooth and oxide-free interface and prevents formation of process-induced damage. It produces firm Fermi level pinning which was previously possible only by ultrahigh-vacuum (UHV) processes.
Temperature Dependence of Boron Adsorption during HBO2 Irradiation on Si(111) Surface Evaluated by Reflection High-Energy Electron Diffraction
Authors: Kumagai Yoshinao , Ishimoto Kouichi , Ryosuke Mori Ryosuke Mori , Fumio Hasegawa Fumio Hasegawa
Published: October 2002

Adsorption of boron on Si(111) surface during HBO2 irradiation was evaluated by reflection high-energy electron diffraction (RHEED). At the substrate temperature above 700°C, RHEED specular beam intensity decreased to a minimum value at boron coverage of 1/3 monolayer (ML), and then increased to the initial value (1 ML coverage). On the other hand, when the substrate temperature was below 700°C, intensity did not recover to the initial value due to the simultaneous surface oxidation. From the temperature dependence of the adsorption rate, the activation energy of the boron adsorption on Si(111) surface was estimated to be 1.2 eV.
Organic Molecular Beam Deposition of α-Sexithienyl
Authors: Hamano Kouji , Kurata Tetsuyuki , Shigeru Kubota Shigeru Kubota , Hiroshi Koezuka Hiroshi Koezuka
Published: October 2002

We fabricated the molecular-oriented thin films of α-sexithienyl (6T) by an organic molecular beam deposition (OMBD) technique. The molecular orientations were evaluated from electronic spectra. The 6T molecules were aligned almost exactly parallel to the surface normal in the film deposited at a low deposition rate under 10-9 Torr. Furthermore, the 6T molecules in the film fabricated under 10-9 Torr have been found to form uniform aggregates. The aggregation has been analyzed by a molecular exciton model to give the molecular tilt angle of 85.7°.
Incorporation of Group-V Elements in GaxIn1-xAsyP1-y Layers Grown on GaAs by Gas-Source Molecular Beam Epitaxy
Authors: Zhang G. , H. Asonen H. Asonen , M. Pessa M. Pessa
Published: October 2002

We have studied incorporation of arsenic and phosphorus in Ga

x

In1-
x

As

y

P1-
y

layers, which are lattice-matched to GaAs substrates, grown by gas-source molecular beam epitaxy. The incorporation behavior of group-V molecules in these layers is found to be quite different from those observed for Ga

x

In1-
x

As

y

P1-
y

lattice-matched to InP, GaAs

y

P1-
y

or InAs

y

P1-
y

materials. We have observed that the incorporation efficiency of arsenic, S (As), is only 1 to 3 times that of phosphorus, S (P). S (As) and S (P) are affected by the relative concentration of Ga and In in the layer and the growth rate of the layer, S (As) increases with indium concentration. S (P)/S (As) increases as the growth temperature increases in the range from 440 to 545° C. These results provide a useful guide to precisely control the group-V composition in Ga

x

In1-
x

As

y

P1-
y

grown on GaAs.
High-Temperature Superconducting Meander Line Resonators with YBa2Cu3O7-δ Films
Authors: Hong Jin Pyo , Moon Chang Wook , Park Chan Hoon , Lee Eun Hong , I. Hun Song I. Hun Song , Jo Won Lee Jo Won Lee
Published: October 2002

High T
c superconducting meander line resonators have been successfully fabricated and characterized using off-axis RF sputtered YBa2Cu3O7-δ films deposited on LaAlO3 substrates. We have made special test fixtures for the resonator measurements. The superconducting resonators with microstrip line structures show significant improvement in the Q-factor (15-fold at 450 MHz) over identical gold resonators. The shift of resonant frequencies with temperatures was observed up to transition temperature (T
c=82 K). Twelve modes of resonant frequencies have been measured in the frequency range of 0.3 to 4 GHz. Input power dependence of surface resistance (R
s) was also determined.
Heat Treatment and Steaming Effects of Silicon Oxide upon Electron Dissipation on Silicon Oxide Surface
Authors: Uchihashi Takayuki , Okusako Takahiro , Sugawara Yasuhiro , Yamanishi Yoshiki , Oasa Takahiko , Seizo Morita Seizo Morita
Published: October 2002

We investigated heat treatment and steaming effects of silicon oxide upon the surface dissipation of contact-electrified electrons. As a result, we found that the surface diffusion of densely contact-electrified electrons on the silicon oxide surface becomes slower due to the removal of the adsorbed water layer on a silicon oxide layer by means of heat treatment, while it is enhanced by the steamed water layer. From the heat treatment and steaming effects upon the dissipation process, we concluded that the stable state of densely contact-electrified electrons becomes more stable upon removal of the water layer.
Variable-Sensitivity Photodetector of pn-np Structure for Optical Neural Networks
Authors: Funatsu Eiichi , Hara Kunihiko , Toyoda Takashi , Jun Ohta Jun Ohta , Kazuo Kyuma Kazuo Kyuma
Published: October 2002

A new structure of the variable-sensitivity photodetector (VSPD) is proposed. It is based on an interdigital pn-np structure. Analog and bipolar photosensitivities varied by the control voltage are described, and the photocurrent is compared with those of the metal-semiconductor-metal (MSM)-type VSPD. Introduction of the pn-np structure is effective for obtaining high photodetection efficiency, and also for modifying the variable-sensitivity characteristics. These advantages make it attractive for optical implementation of neural networks.
High-Pressure Synthesis of Superconducting (Cu, C)-1212 Compound (Cu, C)Ba2(Y, Ca)Cu2Oz
Authors: Akira Ono Akira Ono , Shigeo Horiuchi Shigeo Horiuchi
Published: October 2002

Superconducting 1212 phases, (Cu, C)Ba2(Y, Ca)Cu2O

z

, were synthesized for the first time. Superconducting transition temperatures ( T

c
s) of the Ca-containing 1212 phases are ∼ 80 K regardless of considerable variations in Ca and C contents, while T
c is 45 K for the Ca-free 1212 phase. The low T
c is due to the high Y content of the Ca-free 1212 phase. A structural difference was found between C-rich and C-poor 80 K phases by electron microscopy; the former showed 3 a- and 2 a-type satellites, while the latter did not.
Method of Studying Surface Torsional Anchoring of Nematic Liquid Crystal
Authors: Jiang Min , Wang Zongkai , Sun Ruipeng , Ma Kai , Renxiang Ma Renxiang Ma , Ximin Huang Ximin Huang
Published: October 2002

In this paper we introduce a method to study surface torsional anchoring of both chiral-molecule-doped and pure nematic liquid crystal (NLC) without using any extra field. By measuring the transmission of the twisted or supertwisted NLC cells, the actual twist angles in NLC cells are obtained, which differ from the angle between two boundary rubbing directions. A theoretical discussion reveals the relationship of the surface torsional anchoring energy and the difference, and thus the surface torsional anchoring energy can be calculated.
Depth Profiling of Oxygen Concentration of Indium Tin Oxide Films Fabricated by Reactive Sputtering
Authors: Honda Shinichi , Tsujimoto Akira , Michio Watamori Michio Watamori , Kenjiro Oura Kenjiro Oura
Published: October 2002

Depth profiling of the oxygen concentration of indium tin oxide (ITO) films on glass substrates has been investigated using a high-energy ion beam. Hot-cathode Penning-discharge sputtering (HC-PDS) in the mixed gases of argon and oxygen was applied to fabricate the films. It is found that there is a correlation between the depth profile of oxygen concentration and the electrical properties. The effect of partial pressures of oxygen gas on the depth profile of the oxygen concentration and on electrical properties is discussed.
Radical Control by Wall Heating of a Fluorocarbon Etching Reactor
Authors: Ito Satoshi , Keiji Nakamura Keiji Nakamura , Hideo Sugai Hideo Sugai
Published: October 2002

The entire vessel of a RF diode etching reactor was heated to control the radical composition of a CF4/H2 plasma. Appearance mass spectrometry revealed that the CF3 and CF2 densities are 2 to 3 orders of magnitude higher in the heated reactor at 230°C, compared with the conventional reactor at 30°C. On the other hand, the F atom density monitored by an actinometry technique is almost unchanged. The temporal variation of the CF3 and CF2 densities induced by H2 addition is relatively smaller in the heated environment. A few mechanisms for the anomalous increase of the CF

x

radical are discussed in view of the radical surface loss and the electron-impact radical production. As a consequence, wall heating is useful for controlling the etching processes by enhancing the carbon-containing radicals.
Residual Compression in Ni Film Prepared by Laser Ablation
Authors: Ezumi Susumu Keitoku
Published: October 2002

Large residual compression with the value of (3∼4)109 N/m2 has been observed in Ni films prepared by the laser ablation method using a YAG laser. The origin of compression has been discussed based on the results of X-ray diffraction, streak image of ablated particles and spectrum of the plume. These experiments showed that excited Ni atoms combined with nitrogen remaining in the vacuum chamber and formed nitride ( Ni3N) which caused compression in the film.
Fe-Cluster Structure in Giant Magnetoresistive Fe14Ag86 Granular Thin Film
Authors: Xu Yingfan , Sakurai Masaki , Makhlouf Salah A. , Wakoh Kimio , Kenji Sumiyama Kenji Sumiyama , Kenji Suzuki Kenji Suzuki
Published: October 2002

High-resolution transmission electron microscopy and extended X-ray absorption fine structure analysis have been used for investigation of granular Fe14Ag86 thin film prepared by sputtering and annealing. In the as-deposited state, Fe atoms are randomly distributed in the Ag matrix, yielding spin-glass aspects at low temperatures. After annealing the film at 573 K for 10 min, fine grains whose sizes are about 1 nm are formed and smaller Fe clusters are dispersed in these grains. Higher-temperature annealing leads to grain growth, interface sharpening and formation of bcc Fe clusters. These results are well correlated with the changes in the giant magnetoresistance: the interfacial spin-dependent scattering is enhanced by annealing at 573 K, while it is suppressed by annealing at higher temperatures.
Effect of Atomic and Molecular Hydrogen Irradiation on Ge Surface Segregation during Si Molecular Beam Epitaxy
Authors: Nakagawa Kiyokazu , Nishida Akio , Yoshinobu Kimura Yoshinobu Kimura , Toshikazu Shimada Toshikazu Shimada
Published: October 2002

To study hydrogen irradiation effects on Ge surface segregation during Si molecular beam epitaxy, we introduced molecular and atomic hydrogen into a molecular beam epitaxial growth chamber and found that surface segregation is strongly suppressed by atomic hydrogen irradiation, while it is slightly suppressed by molecular hydrogen irradiation. Molecular hydrogen is thought to dissociate into atomic hydrogen at the substrate surface and has the same effect as atomic hydrogen. We believe segregation is suppressed because hydrogen irradiation limits the surface migration of Si and Ge atoms.
Defects Introduced by Ar Plasma Exposure in GaAs Probed by Monoenergetic Positron Beam
Authors: Uedono Akira , Kawano Takao , Tanigawa Shoichiro , Wada Kazumi , Nakanishi Hideo
Published: October 2002

Ar-plasma-induced defects in n-type GaAs were probed by a monoenergetic positron beam. The depth distribution of the defects was obtained from measurements of Doppler broadening profiles of the annihilation radiation as a function of incident positron energy. The damaged layer induced by the exposure was found to extend far beyond the stopping range of Ar ions, and the dominant defects were identified as interstitial-type defects. After 100°C annealing, such defects were annealed. Instead, vacancy-type defects were found to be the dominant defects in the subsurface region.
Fabrication of GaInAs/GaInAsP/InP Multi-Quantum-Wires and -Boxes by Substrate-Potential-Controlled Electron Cyclotron Resonance
Authors: Kudo Koji , Nagashima Yasuaki , Tamura Munehisa , Tamura Shigeo , Ubukata Akinori , Arai Shigehisa
Published: October 2002

GaInAs/GaInAsP multi-quantum-wires and -boxes with the size of 20-30 nm and aspect ratio greater than 6 were fabricated by combining electron beam lithographt and substrate-potential-controlled electron cyclotron resonance (ECR) dry etching. The photoluminescence (PL) at 77K was observed from the buried multi-quantum wires regrown by OMVPE. The PL intensity of the multi-quantum-wire sample, normalized by the space filling factor of the active region, was 66% of that of the multi-quantum-film structure before etching, which confirms the low-damage feature of this fabrication process.
Influence of Minority Hole Injection on Current Gain Characteristics in AlGaAs/GaAs Heterojunction Bipolar Transistors
Authors: Ito Hiroshi , Nagata Koichi , Osaake Nakajima Osaake Nakajima , Tadao Ishibashi Tadao Ishibashi
Published: October 2002

The influence of the emitter layer structure on the current-gain emitter-size effect in AlGaAs/GaAs HBTs is investigated. Three types of HBTs were fabricated and the recombination current per unit length at the emitter mesa periphery (I
L) was compared. The increase in I
L with decreasing extrinsic-base surface-passivation-layer width is remarkably larger in the fully graded emitter HBTs than in those with abrupt emitters. The contribution of minority hole injection from the base to the emitter-sidewall surface-depletion layer through the potential saddle point is found to consistently explain the experimental results.
Characterization of Epitaxially Grown CeO2(110) Layers on Si by Means of Shadowing Pattern Imaging with Fast Ion Beams
Authors: Inoue Tomoyasu , Kudo Hiroshi , Fukusho Taro , Ishihara Toyoyuki , Tetsu Ohsuna Tetsu Ohsuna
Published: October 2002

Shadowing pattern imaging using keV secondary electrons induced by 56 MeV O8+ ions has been applied to investigate the texture structure of epitaxially grown CeO2(100) layers on Si(100) substrates. The observed shadowing pattern is characteristic of the crystal with a domain structure, i. e., a clear <110> axial image and smeared planar images, which result from the overlapping of two kinds of planar patterns (one is rotated 90° from the other around the <110> axis). The results are consistent with the observations by high-resolution secondary electron microscopy and reflection high-energy electron diffraction.
New Series of High Tc Superconductors, GaSr2Can-1CunO2n+3 (n=3; Tc=70 K, n=4; Tc=107 K) Prepared at High Pressure
Authors: Takayama-Muromachi Eiji , Isobe Masaaki
Published: October 2002

A new series of superconductors, GaSr2Ca

n
-1Cu

n

O2
n
+3 ( n=3, 4), were prepared under a high pressure of 6 GPa at 1250°C. The n=4 member becomes superconducting below 107 K while the n=3 one below 70 K. From an analogy with the structure of the Ga-1212 phase, their X-ray patterns were indexed assuming orthorhombic lattices with the space group of I2 mb( Ima2, No. 46): a=5.454(1), b=5.391(1) and c=29.371(6) Å for the n=3 member and a=5.462(4), b=5.417(4) and c=35.78(5) Å for the n=4 one. They have structures closely related to those of Tl (or Hg)-1223 and 1234 phases.
Adhesion of Photoresist Pattern Baked at 80 to 325° C to Inorganic Solid Surface
Authors: Kawai Akira , Nagata Hitoshi , Takata Hiroaki Morimoto
Published: October 2002

Adhesion of positive photoresist films which were baked at 80 to 325° C on inorganic surfaces is analyzed with respect to thermodynamics. The peeling strength of resist/solid surface systems shows a minimum value for a baking temperature range from 150 to 200° C. It is found that the hydrogen bonding interaction of resist/surface system mainly affected the adhesion phenomena.
Direct Bonding of LiTaO3 Single Crystals
Authors: Tomita Yoshihiro , Sugimoto Masato , Okano Kazuo Eda
Published: October 2002

A new fabrication method for combining lithium tantalate single crystals by direct bonding without using bonding agents has been developed. The bonded interface was found to be very uniform, and bonding on an atomic scale was achieved in spite of a relatively low heat-treatment temperature of 350°C. This method is very promising for realizing new stacked structures and new fabrication processes for piezoelectric and electrooptic devices, such for a layer of ferroelectric single crystal on insulator or semiconductor.