bluuebunny/crossref_metadata_2025 huggingface dataset:
Sidewall Recombination Velocity in GaInAsP/InP Quantum-Well Lasers with Wire-like Active Region Fabricated by Wet-Chemical Etching and Organo-Metallic Vapor-Phase-Epitaxial Regrowth
Authors: Munehisa Tamura Munehisa Tamura , Takashi Kojima Takashi Kojima , Toshikazu Ando Toshikazu Ando , Nobuhiro Nunoya Nobuhiro Nunoya , Shigeo Tamura Shigeo Tamura , Shigehisa Arai Shigehisa Arai
Published: October 2002

We estimated the nonradiative recombination velocity at the sidewall of GaInAsP/InP
quantum-well lasers with narrow wire-like active region, which had been fabricated by wet-chemical
etching and two-step organo-metallic vapor-phase-epitaxial (OMVPE) regrowth, from
the active region width dependence of spontaneous emission efficiency under current
injection. It was shown theoretically that this estimation method of the nonradiative
recombination velocity is more accurate than a conventional method using
threshold current dependence on the width of an active region, and was
confirmed experimentally. The sidewall recombination velocity of 5 stacked
multiple-quantum-well and a single-quantum-well structures fabricated by
wet-chemical etching and OMVPE regrowth method was estimated to be
1.3 ×103 cm/s and 2.0 ×103 cm/s, respectively, at room
temperature, while it was estimated to be very small (less than 10 cm/s) at low
temperatures (T = 90 K).
Negative Creeping Discharge Characteristics of a Gas/Solid Composite Insulation System under Pulse Voltages
Authors: Ueno Hideki , Watabe Katsunori , Tada Kazuya , Onoda Mitsuyoshi , Nakayama Hiroshi
Published: October 2002

Creeping discharge characteristics of a composite gas/solid insulating system have
been studied by inserting a solid insulator between a needle electrode and a plane electrode.
Considerable differences have been found in the creeping discharge behaviors of N2/SF6 and
CO2/SF6 systems. With the addition of three-percent of SF6 gas to CO2 gas, the creeping
discharge of the CO2/SF6 gas mixture was clearly seen to be strongly affected by the nature
of SF6 gas, as revealed by photon emission measurements in a corona and observations using
an ultrahigh-speed digital imaging system. On the other hand, the addition of a small amount
of SF6 to N2 caused a significant decrease in the flashover voltage and a peculiar creeping
corona extension. The creeping discharge characteristics of N2/O2 mixtures are similar to that
observed in N2/SF6 mixtures. Both an electronegative gas (negative ion) and nitrogen play
important roles in this behavior.
Simple Hexagonal Coulomb Crystal near a Deformed Plasma Sheath Boundary in a Dusty Plasma
Authors: Kazuo Takahashi Kazuo Takahashi , Tomoko Oishi Tomoko Oishi , Ken-ichi Shimomai Ken-ichi Shimomai , Yasuaki Hayashi Yasuaki Hayashi , Shigehiro Nishino Shigehiro Nishino
Published: October 2002

Simple hexagonal Coulomb crystals have been
observed near a deformed plasma sheath boundary in a dusty plasma.
It seems that particle rows, which are found in the
direction perpendicular to an electrode in the Coulomb crystal, are
formed due to not only Coulomb repulsive forces but also some
attractive forces. In this study, experiments using the deformed
sheath revealed that the rows
were bent along the direction of electric fields and ion flows in a
plasma. The result shows that sheath
structures and shapes affect Coulomb crystal structures in dusty plasmas. In
this paper, the formation of the particle rows are discussed, where balances of forces on
particles in a dusty plasma are taken into account under the
assumption that wake potentials related to ion flows exist in the sheath
region.
Gradation Stitching Exposure for Step-and-Scan Projection Printing System
Authors: Horiuchi Toshiyuki
Published: October 2002

A new step-and-scan exposure method for enlarging the field size is proposed.
The design and fabrication of projection exposure optics with a large field is difficult,
especially for short wavelengths, and the exposure field should be kept as small as
possible for obtaining high resolution, insuring sufficient depth of focus and decreasing
the distortion of the optics. However, developing more advanced devices requires large
chips. Thus, field stitching is investigated to resolve this inconsistency. In the new
method, by generating gradation at the stitched boundaries and keeping the
overlapping length long, the exposure dose continuity becomes very good, and stitching
notches do not form. However, intensity distribution degradation, pattern position
shift and contrast deterioration, which are dependent on stitching errors, should be
taken into consideration to maintain the pattern quality within an acceptable range.
Calculations indicate that the stitching errors should be suppressed to below about
0.2u, where u=λ/2NA is comparable to the resolution limit.
Low Bias Voltage Dry Etching of InP by Inductively Coupled Plasma Using SiCl4/Ar
Authors: Matsutani Akihiro , Koyama Fumio , Iga Kenichi
Published: October 2002

We have demonstrated anisotropic and smooth etching of InP by an inductively coupled plasma (ICP) method using SiCl4/Ar and processing at a high substrate temperature. We measured the etching rate by varying the substrate temperature, process pressure and rf power. Vertical micropillars of InP with smooth etched surfaces were obtained under relatively small dc biases of lower than -50 V. The ICP etching is considered to be useful for low-damage microfabrication of InP systems by optimizing the etching condition.
Mask Patterning Challenges Beyond 150 nm
Authors: Gesley Mark
Published: October 2002

Mask patterning strategy must anticipate future requirements and be flexible enough to accommodate the broad range of options currently confronting the industry. The assessment and prioritization of the technical challenges for mask pattern generation are based on three attributes: lithography quality, throughput, and pattern processing complexity. A systems approach to integrating these features is guided by an error budget and evaluation of the various tradeoffs to identify and, if possible, optimize
the total tool and process solution that meets the critical customer needs in semiconductor
manufacturing.
This paper evaluates several key drivers influencing pattern generation technology. Writing strategy that can achieve requisite pattern fidelity and throughput is considered. This paper discusses evolution of the
pixel concept, design grid, and beam spot size. It also considers the growing complexity of error budget terms needed to meet composite lithographic specifications. It gives several examples of important error
budget contributors and includes the relation of aerial image slope, deposited dose, and critical
dimension transferred to the mask. Observations are made about the required data path channel capacity as pattern processing complexity grows.
An evolutionary systems architecture that meets the increasingly complex demands of the technology
roadmap is summarized.
Determination of the Critical Dimension and Proximity Bias Variations Across the Lens Field by Electrical Linewidth Measurements
Authors: Toublan Olivier , Boutin Daniel , Schiavone Patrick
Published: October 2002

Electrical critical dimension (CD) measurements are now widely used as a characterization technique in optical lithography. In this paper this technique is applied to the determination of the CD and proximity bias variations across the lens field. A method, based on statistical considerations, is introduced to decorrelate the contribution of the mask to the
global Across Field linewidth variation (AFLV). It is shown that the mask CD dispersion has an important contribution in the total CD range observed on the wafer. By using this technique, a lens quality determination has been done and the optical contribution to the field CD dispersion has been determined. Moreover, because it is a fast and accurate technique, we
show that electrical linewidth measurements can be used in a lens characterization procedure. Results obtained indicate that the proximity bias dispersion across the lens field is not negligible and the question of a dependent field position correction is raising up.
Sub-0.1-µm-Pattern Fabrication Using a 193-nm Top Surface Imaging (TSI) Process
Authors: Mori Shigeyasu , Kuhara Koichi , Morisawa Taku , Matsuzawa Nobuyuki , Endo YukoKaimoto , Matsuo Takahiro , Sasago Masaru
Published: October 2002

This paper presents a 193-nm top surface imaging (TSI) process for the
sub-0.10-µm-device rule. The process achieved a 0.07-µm contact hole,
0.04-µm isolated line, and 0.06-µm space pattern without the need for any
optical resolution enhancement technique. An exposure latitude of ±10%
was obtained for the process with a 0.10-µm contact hole. We can obtain a
sufficient depth of focus (DOF) by using an attenuated phase-shifting mask.
We resolved a 0.085-µm line-and-space pattern by using an alternative
phase-shifting mask, and obtained a 0.8-µm DOF for a 0.09-µm line-and-space
pattern, using an alternative phase-shifting mask. We demonstrated the
fabrication of sub-0.10-µm line-and-space binary patterns. Sub-0.10-µm
patterns were produced by using the TSI process for 193-nm lithography.
Subwavelength Pattern Transfer by Near-Field Photolithography
Authors: Ono Takahito , Esashi Masayoshi
Published: October 2002

The subwavelength patterns beyond the diffraction limits were successfully transferred by using an
evanescent field generated near metal slits. For this purpose, masks having metal slits and apertures were
fabricated using an electron beam (EB) and an atomic force microscope (AFM). An AFM-based
fabrication method was applied to fabricate small apertures of which the minimum diameter was below 50 nm. UV light was illuminated using a mercury lamp by keeping the mask in contact with a wafer on which
a conventional photoresist was coated. To obtain a small pattern, close contact between the mask and the
substrate was required. A deformable silicon diaphragm was effective for this purpose. Subwavelength
patterns having a size below 200 nm were successfully transferred onto the conventional photoresist
beyond the diffraction limits of light. Furthermore, it was found that the polarized light decreased the size
of transferred patterns due to enhancement of near-field localization and reduction of far-field effect.
Simple Method for Resist Critical Dimension Prediction
Authors: Nakao Shuji , Mastubara Hiroshi , Yamaguchi Astumi , Sakai Junjiroh , Nakae Akihiro , Tatsu Shin-ichirou , Tsujita Kouichirou , Wakamiya Wataru
Published: October 2002

A simple calculation method which predicts resist
critical dimension (CD) with high precision is proposed. To
simplify the formalism, the image intensity profile and
dissolution rate variation of the resist are approximated
with a linear and an exponential function, respectively.
And the three step development approximation, in which
development is assumed to proceed only vertically in the
first step, only horizontally with a varying development
rate in the second step and also horizontally with a
constant rate in the third step, is adopted. With these
simplifications, the resist edge displacement is expressed
with a primitive formula. This method is examined by
comparing the experimental and calculated results,
confirming the effectiveness of the method.
Chemical Vapor Deposition of TiN Films from Tetrakis(ethylmethylamido)titanium and Ammonia
Authors: Lee Jae Gab , Choi Jung Hwan , Lee Chongmu , Hong Ju Hwa , Lee Eun Gu , Shin Hyun Kook , Hong Hae Nam
Published: October 2002

TiN films were prepared using a new Ti precursor, tetrakis(ethylmethylamido)titanium (TEMAT) and
ammonia. The premixing of NH3 and TEMAT provided the control over the gas phase reaction of the two
reactants to generate the intermediates required for the deposition of high-quality TiN films. Film resistivities
of 800–1200 µ Ω-cm and low levels of impurities were obtained in TiN films deposited under the condition of
low NH3/TEMAT ratios, wafer temperature of 350°C and total reactor pressure of 1 Torr. In addition, the
introduction of a small amount of ammonia improved the diffusion barrier property for Cu metallization up to
600°C. Slight degradation in the conformality of TiN films was observed at the low ratio of NH3/TEMAT.
Furthermore, the addition of NH3 tended to improve the surface morphology of TiN films and did not cause any
particle generation due to the low process pressure of 1 Torr. X-ray photoelectron spectroscopy (XPS) analysis
revealed the role of ammonia in the homogeneous reaction.
The Optimization of the Deposition Variables for High Photoconductivity a-Si:H Films Prepared by Electron Cyclotron Resonance Plasma Chemical Vapor Deposition
Authors: Moonsang Kang Moonsang Kang , Yongseo Koo Yongseo Koo , Chul An Chul An
Published: October 2002

The physical parameters of the amorphous silicon films with high photoconductivity of 10-5–10-4 (Ωcm)-1 were optimized in the range of the various experimental conditions using electron cyclotron resonance plasma chemical vapor deposition. Films with high photoconductivity shared the following properties with each other: the optical band gap was 1.7–1.8 eV, FWHM was below 75, the ratio of dihydride to the monohydride was 1–1.5 and hydrogen content was 18–24 at.%.
Stress Behavior of High Density Plasma Chemical Vapor Deposition Oxide Deposited on a Metal-Patterned Wafer
Authors: Lee Soo Geun , Park Jong Wang , Kim Min , Kim Sun Rae , Seo Tae Wook , Chung U-In , Kang Geung Won
Published: October 2002

A high density plasma chemical vapor deposition (HDPCVD) oxide was used as an inter metal
dielectric (IMD) due to its good gap-fill properties for compensating the tensile stress of Al metal layers.
When the HDPCVD oxide was deposited on a metal patterned wafer, however, the oxide showed tensile
stress. In order to understand the mechanism of the characteristic stress behavior of the HDPCVD oxide on
a metal patterned wafer, the change in magnitude of the wafer bow was measured as a function of oxide
thickness, and was modeled quantitatively using the density of metal patterns and the stress change of the
metal film. In the model, the oxide deposited between metal lines was assumed to have tensile stress due
to the relatively high shrinkage of the neighboring metal pattern. When the deposited HDPCVD oxide
thickness was thinner than that of the metal film, only the stress of the lower parts of the metal film,
which was connected to the oxide, could affect the change of the wafer bow value. When the
deposited oxide thickness was greater than that of the metal film, the stress of the oxide above the metal
film was assumed to be compressive. Using the above assumptions and a simple mathematical model, the
change in magnitude of the wafer bow was calculated and compared with experimental results. The
calculated data were in good agreement with the experimental values.
Measurement of Secondary Electron Emission Coefficient (γ) of MgO Protective Layer with Various Crystallinities
Authors: Choi Eun-Ha , Oh Hyun-Joo , Kim Young-Guon , Ko Jae-Jun , Lim Jae-Yong , Kim Jin-Goo , Kim Dae-Il , Cho Guangsup , Kang Seung-Oun
Published: October 2002

The secondary electron emission coefficient γ of a MgO protective layer with various crystallinities has
been successfully measured by the γ-focused ion beam system with complete
elimination of the charge accumulation problem by scanning-area adjustment techniques. It is found that the (111) surface
has the highest γ from 0.14 to 0.26 in comparison with the other films with (200) and (220)
crystallinities for operating
Ne+ ions, while ranged from 0.03 to 0.24 for Ar+ ions, under operating ion energies
from 50 eV to 500 eV throughout this experiment.
These observations explain why the (111) crystallinity
of the MgO protective layer plays an important role in lowering the firing voltages in AC plasma display panel
compared to the films with other crystallinities.
Analysis of the Image Formation Mechanism on High Energy Scanning Electron Microscopy
Authors: Kotera Masatoshi , Yamaguchi Kiyoshi
Published: October 2002

The image formation mechanism of the high-energy scanning electron microscopy is analyzed by a Monte Carlo simulation of electron trajectories in a specimen. It is shown that only secondary electrons which are produced directly by incident primary electrons carry information of the three-dimensional hole structure at the specimen surface. The major contribution to the signal is due to the secondary electrons emitted from the side-wall of the hole. Even if the hole is covered by a 30-nm-thick carbon film, the edge contrast of the hole is appreciable as the primary electron is incident normal to the surface. If there is an aperture in the film covering the hole, secondary electrons from the side-wall of the hole contribute to the signal.
Accurate Determination of Low-Level Radon Concentration in Water by Means of γ-Ray Spectrometry
Authors: Hamanaka Shunichi , Shizuma Kiyoshi , Wen Xiao-qiong , Iwatani Kazuo
Published: October 2002

A solvent extraction method combined with γ-ray spectrometry has been applied to the measurement of low-level radon concentration in water. Radon in 900 mL of water was extracted into 120 mL of organic solvent. The radon content was derived from γ-ray spectrometry of daughter nuclides 214Pb and 214Bi. Extraction rates defined by the ratio of the extracted radon amount to that in the original sample of water were experimentally determined to be 0.758±0.020 for xylene and 0.671±0.018 for toluene. The detection limit of the radon concentration measurement was 0.082 Bq L-1 using the xylene extraction method. This method has been applied to the measurement of the radon concentration in tap water.
Controlled Nitrogen Incorporation at Si–SiO2 Interfaces by Remote Plasma-Assisted Processing
Authors: Koh Kwangok , Niimi Hiro , Lucovsky Gerald , Green Martin. L.
Published: October 2002

This paper presents experimental studies in which N-atoms have been incorporated at Si–SiO2 interfaces by forming the interface and oxide film by a 300°C remote plasma assisted nitridation/oxidation process using N2O. Process dynamics have been studied by on-line Auger electron spectroscopy (AES) by interrupted plasma processing. Based on AES studies using N2O, O2 and sequenced N2O and O2 source gases, reaction pathways for i) N-atom incorporation at and/or ii) removal from buried Si–SiO2 interfaces have been identified, and contrasted with reaction pathways for nitridation using conventional furnace processing.
Two-Input Axis Angular Rate Sensor
Authors: An Seungdo , Oh Yongsoo , Choi Sang-on , Song Ci-moo
Published: October 2002

A vibrating angular rate sensor is developed by the polysilicon surface micromachining process.
The 7.0 µm-thick polysilicon layer is deposited by low-pressure chemical vapor deposition (LPCVD)
and is suspended by sacrificial oxide wet etching after patterning by reactive ion etching. The
angular rate sensor uses angular resonance for the driving and sensing modes. The two-degenerate
sensing modes enable the sensor to detect the angular rate inputs from each orthogonal substrate
rotation. In view of cost and size, one sensor chip is preferable to two sensor chips orthogonally-configured
for the detection of two-input axis angular rate. The Coriolis motion arising from the
angular rate causes the capacitance change and is converted to voltage change with signal
conditioning hybrid application-specific integrated circuit (ASIC). The performance of the
angular rate sensor is degraded by air damping, so the sensor element is housed in a high vacuum
chamber for a high quality (Q) factor. The angular rate sensor has an active structure element less
than 1mm2 in size and shows a noise equivalent signal of 0.1 deg/s.
Self-Organizing Process of Moderately Strained Zn1-xCdxSe Layer Grown on GaAs(110) by Molecular Beam Epitaxy
Authors: Ko Hyun-Chul , Fujita Shigeo
Published: October 2002

Self-organizing process of moderately strained Zn1-x
Cd
x
Se layer on the GaAs(110)
surface was investigated during the molecular beam epitaxy (MBE). The GaAs(110)
surface was prepared by cleavage in ultrahigh vacuum (UHV). In contrast to the ZnSe
layers which have a mirror-like surface, two types of surface structures were observed
on the Zn1-x
Cd
x
Se layer, i.e. pyramidal-shaped islands and asymmetric Δ-shaped ridges
oriented parallel to the [110] direction, indicating that the strain relaxation process was
not of a conventional Stranski-Krastanow type. The ridges were strong correlated with
the underlying dislocations produced by anisotropic in-plane strain relaxation. Local
variation in the growth rate due to periodic strain distributions caused by the
dislocations is suggested to be the formation mechanism of the ridge structures.
A Nano-Structure Memory with Silicon on Insulator Edge Channel and a Nano Dot
Authors: Park Geunsook , Hwang SangyeonHan , Shin Hyungcheol
Published: October 2002

We fabricated nano structure memory with silicon on insulator
(SOI) edge channel and a nano dot. The width of the edge channel was
determined by the thickness of the recessed top-silicon layer of SOI
wafer and the size of sidewall nano dot was determined by the reactive
ion etching (RIE) etch and E-beam lithography. The memory has the threshold voltage shift of about 1 V for maximum programming voltage of 7 V and showed reasonable retention and endurance characteristics.
Coefficient of Kinetic Friction of Snow Skis during Turning Descents
Authors: Sahashi Toshio , Ichino Shoji
Published: October 2002

On a snow plane, descents were performed by snow plows, stem turns, parallel turns and wedelns. The descents were photographed in sequence and these were used to draw the loci of the skis. Coefficients of kinetic friction between the skis and the snow during the turns were obtained from the loci; their values were between 0.01 and 0.3.
Scanning Tunneling Microscopy Study of GaAs (001) Surfaces Grown by Migration-Enhanced Epitaxy at Low Temperatures
Authors: Daiichi Suzuki Daiichi Suzuki , Hiroshi Yamaguchi Hiroshi Yamaguchi , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

Using a molecular beam epitaxy/scanning tunneling microscopy (MBE/STM) system, we have compared the surface morphology of GaAs grown by MBE and migration-enhanced epitaxy (MEE) at a substrate temperature of 300°C, which is much lower than normal MBE growth temperature. In terms of surface flatness, the difference between MBE and MEE was clearly visible. The surface roughness of MEE-grown GaAs was at most 2-monolayer and the surface was covered with large terraces with small islands on them. On the other hand, in spite of the clear reflection high energy electron diffraction (RHEED) intensity oscillation during the growth, the low-temperature MBE-grown surface was very rough and large terraces could not be seen on the surface. We concluded that these results are due to the differences in the growth mechanisms of MBE and MEE.
Influence of Electron Velocity Overshoot Effect on High-Frequency Characteristics of Quantum Well Infrared Photodetectors
Authors: Maxim Ryzhii Maxim Ryzhii , Irina Khmyrova Irina Khmyrova , Victor Ryzhii Victor Ryzhii
Published: October 2002

We have studied the transient response of AlxGa1-x
As/GaAs quantum well infrared photodetectors (QWIPs) and their high-frequency performance using a self-consistent ensemble Monte Carlo particle method. It has been shown that the photocurrent caused by the electron intersubband transitions under the influence of an ultra-short pulse of infrared radiation reveals a sharp peak followed by relatively slow decay. This is associated with the electron velocity overshoot and the electron transit time and capture effects. The velocity overshoot results in the existence of an additional plateau-like region in the QWIP frequency-dependent responsivity which can correspond to the terahertz range.
Defects and Their Annealing Properties in B+-Implanted Hg0.78Cd0.22Te Studied by Positron Annihilation
Authors: Akira Uedono Akira Uedono , Hiroji Ebe Hiroji Ebe , Masahiro Tanaka Masahiro Tanaka , Shoichiro Tanigawa Shoichiro Tanigawa , Kosaku Yamamoto Kosaku Yamamoto , Yoshihiro Miyamoto Yoshihiro Miyamoto
Published: October 2002

Defects and their annealing properties in B+-implanted Hg0.78Cd0.22Te (p-type) were studied using the positron annihilation technique. For an unimplanted specimen, the major species of defects was identified to be Hg vacancies, V
Hg, and its concentration was estimated to be 6×1015 cm-3. For the B+-implanted specimen, a damaged region showed n-type character, and vacancy-type defects were found to be present in this region. Below the n-type layer, about 50% V
Hg was annihilated by the recombination between V
Hg and Hg atoms. After 150° C annealing, the mean size of open space of the vacancy-type defects in the n-type layer was found to decrease. At the same annealing temperature, the electron concentration in the n-type layer also decreased. Thus, an origin of donors was attributed to interstitial-type defects. The annealing temperature of the vacancy-type defects introduced by ion implantation was determined to be 300° C
Metal Atomic Chains on the Si(100) Surface
Authors: Dong Zhen-Chao , Yakabe Taro , Fujita Daisuke , Ohgi Taizo , Rogers Duncan , Nejoh Hitoshi
Published: October 2002

The selection of a single-domain Si(100)2×1 surface enables us to make an indium atomic chain over 70 nm in length. Such self-assembled chains can be extended by atomic manipulation using a scanning tunneling microscope tip, as briefly demonstrated in this work on In/Si(100). The advantage of a single-domain Si(100) surface over a double-domain one for the growth of long chains is rationalized, and the mechanism behind the atomic manipulation is noted.
Thermal Analysis of Power Devices Wafer-Bonded to High Thermal Conductivity Substrates by Epitaxial Lift-Off
Authors: Chan Winston K.
Published: October 2002

Transferring a thin semiconductor device film from its growth substrate to a substrate with better thermal properties is being explored as a way to improve device performance by decreasing the thermal resistance. To quantify this, the thermal behavior of a power device bonded to a high thermal conductivity substrate is modelled by finite element analysis. We calculate the temperature rise for various bonding geometries, and find some general rules to minimize the temperature rise.
Quantitative Transmission Electron Microscopy Investigation of the Relaxation by Misfit Dislocations Confined at the Interface of GaN/Al2O3(0001)
Authors: Kaiser Stephan , Preis Herbert , Gebhardt Wolfgang , Ambacher Oliver , Angerer Helmut , Stutzmann Martin , Rosenauer Andreas , Gerthsen Dagmar
Published: October 2002

A quantitative transmission electron microscopy (TEM) investigation of the relaxation of GaN grown on Al2O3(0001) has been carried out. Terminating {112̄0}-substrate fringes observed at the interface of the highly mismatched system have been characterized and the efficiency of the relaxation was measured. Wurtzite type GaN was grown by plasma induced molecular beam epitaxy (MBE) on the (0001) basal plane of Al2O3. The in-plane orientation between GaN and substrate reveals a high lattice misfit of f=-13.9% and therefore the critical thickness of dislocation formation is reached when the first monolayer of GaN is grown. An expected interfacial relaxation process is characterized by the results of high resolution transmission electron microscopy (HRTEM) which reveals misfit dislocations confined in the GaN/Al2O3 interface region. The quantitative evaluation of the HRTEM images on the one hand and Moiré pattern on the other hand shows the effectiveness of the observed relaxation process: here a degree of relaxation δ=(-11.8±0.9)% and a residual strain of εr=(-2.1±0.9)% was measured, and it seems that only εr causes a dislocation density of estimately 1010 cm-2 in the GaN epilayer.
Infrared Spectroscopy of the Solid Solution [KxNa1-x]2CO3
Authors: Al-Hawery A. S.
Published: October 2002

A complete infrared study of the mixed crystal systems K2CO3 and Na2CO3 has been carried out in the region of 4000–600 cm-1. The study includes the internal fundamental normal vibrations of the CO3 ion in the ordered phases of the two carbonates at room temperature for different values of potassium concentration. The IR spectra, spectral band shape intensities and frequencies of the internal modes have been studied as a function of the potassium ion concentration.
Effects of Oxidation on Electrical Conduction and Breakdown of Low-Density Polyethylene Films with Different Densities
Authors: Banmongkol Channarong , Mori Tatsuo , Mizutani Teruyoshi , Ishioka Mitsugu , Ishino Iwao
Published: October 2002

Oxidation more greatly enhanced the conduction current in low-density polyethylene with a low density of 0.9172 g/cm3 (ℓ-LDPE) than that with a high density of 0.9255 g/cm3 ( h-LDPE). This result was attributed to the easier carrier transport in the unoxidized region of ℓ-LDPE. Both oxidized specimens had almost the same impulse breakdown strength (F
Bimp), except when the absorbance of carbonyl groups (A) was higher than 0.6. At 30°C, the increase in the number of injected electrons which initiate an avalanche decreased F
Bimp for A<0.1 but the carrier scattering effect due to carbonyl groups increased F
Bimp for A>0.1. However, a thermal or electromechanical breakdown mechanism would take part in the breakdown process at higher temperatures. The dc breakdown strength (F
Bdc) decreased with oxidation, and h-LDPE showed a higher F
Bdc than ℓ-LDPE. These results suggested a contribution of the thermal mechanism to the breakdown. Space charge also seemed to play a role in the breakdown process.
Small Liquid Crystal Droplet Formation of Polymer-Dispersed Liquid Crystal under Ultraviolet Light Irradiation without Short Wavelength Component
Authors: Fujikake Hideo , Takizawa Kuniharu , Kikuchi Hiroshi , Fujii Takanori , Kawakita Masahiro , Aida Tahito
Published: October 2002

The light scattering properties and polymer morphology of polymer-dispersed liquid crystal films were investigated while adjusting the spectrum of ultraviolet light irradiation with several optical filters in their formation process of photopolymerization-induced phase separation. It is found that the short wavelength light component of less than 355 nm, which is contained in ultraviolet light to be irradiated, slows the phase separation process and results in the formation of large liquid crystal droplets. The morphological changes in the polymer may be due to undesirable decomposition products created in the nematic liquid crystal under the short wavelength ultraviolet irradiation. A spectral arrangement using an optical filter to eliminate the short wavelength light is useful in obtaining small liquid crystal droplets with a strong light-scattering effect, which increases the extinction ratio of polymer-dispersed liquid crystal films. This formation technique will also improve photochemical damage in the phase separation process.
GaInNAs/GaAs Quantum Well Growth by Chemical Beam Epitaxy
Authors: Miyamoto Tomoyuki , Takeuchi Kanji , Kageyama Takeo , Koyama Fumio , Iga Kenichi
Published: October 2002

This is the first report on chemical beam epitaxy (CBE) of GaInNAs/GaAs quantum wells (QWs). From the observed clear X-ray diffraction satellite peaks, the QW structure incorporating nitrogen supplied by radical nitrogen was successfully grown. The photoluminescence emission with the emission peak wavelength of 1.0 µm was observed from GaInNAs/GaAs QWs at room temperature. The wavelength could be elongated by increasing the amount of nitrogen and indium.
Crystal Structure and Electrical Conductivity of LiN2H5SO4 at High Temperature
Authors: Takanori Fukami Takanori Fukami , Ruey-Hong Chen Ruey-Hong Chen
Published: October 2002

Electrical conductivity, differential scanning calorimetry and X-ray diffraction measurements have been performed on a single crystal of lithium hydrazinium sulfate, LiN2H5SO4, in the temperature range from 295 K to about 470 K. The crystal structures at several temperatures are determined in this temperature range. The structural phase transition is not found, but an abnormal decrease of the electrical conductivity with increasing temperature above 445 K is observed. The relation between the electric properties and the crystal structures of the sample crystal is discussed. The LiN2H5SO4 crystals are suggested to be proton and Li ionic conductors.
Atomic Layer-by-Layer Metal-Organic Chemical Vapor Deposition of SrTiO3 Films with a Very Smooth Surface
Authors: Zaiyang Wang Zaiyang Wang , Shunri Oda Shunri Oda
Published: October 2002

This paper presents the investigation of single-phase SrTiO3 thin films prepared by two methods: the atomic layer-by-layer metal-organic chemical vapor deposition (ALMOCVD) method and the co-deposition MOCVD method, using third generation dipivaloylmethane chelate of strontium (Sr(DPM)2·2tetraene) and titanium tetraisopropoxide as precursors. Compared with co-deposition MOCVD, the SrTiO3 films grown by ALMOCVD on MgO substrates show higher [100] orientation with a value of the full width at half maximum as small as 0.18°, investigated by X-ray diffraction θ–2θ scan, ω-rocking curve analysis and φ scan. Observations with atomic force microscopy also show that the SrTiO3 films have a very smooth surface in which the maximum distance between peaks and valleys is 2.70 nm and the average roughness is 0.37 nm. These results demonstrate that better epitaxial SrTiO3 films, in terms of crystalline quality and surface morphology, can be obtained by ALMOCVD rather than by co-deposition MOCVD. Furthermore, we have investigated that N2O supplied during deposition influences the crystallinity and surface morphology.
Preparation and Piezoresistive Properties of Polycrystalline SnO2 Films
Authors: Yoshiharu Onuma Yoshiharu Onuma , Zhanhe Wang Zhanhe Wang , Hironobu Ito Hironobu Ito , Masato Nakao Masato Nakao , Kiichi Kamimura Kiichi Kamimura
Published: October 2002

Tin oxide thin films were deposited by dc magnetron sputtering in a gas mixture of Ar and O2 using a target containing antimony. The films were characterized using X-ray diffraction. The films showed preferred orientation in a <110 > or <211 > plane. The properties of films depended on the substrate temperature and the gas flow ratio of Ar/O2. The piezoresistive properties of these films have been measured using a conventional cantilever method. The gauge factor was measured to be around negative 5–20 at room temperature, which is comparable to the gauge factor of polycrystalline silicon films.
Electrical Properties of Sc Schottky Barrier Diodes Fabricated on Argon-Ion Sputtered p-GaAs
Authors: Goodman Stewart A. , Auret F. Danie , Deenapanray Prakash N. K. , Myburg Gerrit
Published: October 2002

Epitaxially grown p-GaAs wafers were bombarded with Ar-ions before the deposition of scandium (Sc) on them. Current-voltage (I-V) measurements of these Schottky barrier diodes showed that the barrier height, series resistance and ideality factor were increased as the Ar-ion fluence was increased.
Generation of Interface Traps and Oxide-Trapped Charge in 6H-SiC Metal-Oxide-Semiconductor Transistors by Gamma-Ray Irradiation
Authors: Ohshima Takeshi , Yoshikawa Masahito , Itoh Hisayoshi , Aoki Yasushi , Nashiyama Isamu
Published: October 2002

Enhancement-type n-channel metal-oxide-semiconductor field effect transistors
(MOSFETs) were fabricated on 6H-SiC to investigate the influence of γ-ray irradiation on
device characteristics. The net number of radiation-induced oxide-trapped charges and
interface traps induced by γ-ray irradiation were ∼3×1012/cm2 and ∼5×1011/cm2 after 70 kGy
irradiation, respectively. These were measured from changes in the subthreshold-current curve.
On comparing the densities of oxide-trapped charges and interface traps produced by
irradiation in 6H-SiC MOSFETs with those in Si MOSFETs, the 6H-SiC MOSFETs are found
to have high radiation resistance.
Highly Efficient Electron Emission Diode of Single-Crystalline Chemical-Vapor-Deposition Diamond
Authors: Nishimura Masaki , Hatta Akimitsu , Ito Toshimichi
Published: October 2002

A novel type of flat electron emission diode with a high emission efficiency has
been fabricated using single crystalline diamond thin films homoepitaxially grown on thick
high-pressure-synthesized diamond. For the formation of the buried electrode, 180-keV
N+ ions were implanted into the homoepitaxial layer grown by microwave plasma
chemical-vapor-deposition (CVD) method to a dose 1×1016 ions/cm2 at room
temperature. Since this process created a significant damage in the specimen surface
layer working as the electron emission surface, a high quality diamond layer was
subsequently overgrown to recover the damaged surface. Applying voltages of sub-kV
between the hydrogenated surface and the buried electrode results in an efficient
electron emission (>10%).
Control of Orientation for Polycrystalline Silicon Thin Films Fabricated from Fluorinated Source Gas by Microwave Plasma Enhanced Chemical Vapor Deposition
Authors: Nakahata Kouichi , Miida Atsushi , Kamiya Toshio , Maeda Yoshiteru , Fortmann Charles M. , Shimizu Isamu
Published: October 2002

The structure of polycrystalline silicon films was controlled by selecting deposition conditions,
especially gas mixing ratio of H2/SiF4, for plasma enhanced chemical vapor deposition on glass at a
low temperature of 360°C. Under the H2/SiF4 ratio of 10/90 sccms, (111), (220), (311) and (400)
diffraction peaks were observed by X-ray diffraction for a 0.5 µm thick film and (400) oriented
crystallites grew with film thickness. The sharpness of the Raman peak around 520 cm-1 and the
pseudo-dielectric function measured by an ellipsometer indicated that the crystallites have excellent
regularity of the Si–Si bond compared with (220) oriented films and also have small surface
roughness, which are preferable features for device applications. The selective growth of (400)
oriented grains is thought to partly originate from selective etching due to fluorine related species
generated under low hydrogen conditions.
Metalorganic Molecular Beam Epitaxy of CuInSe 2 on GaAs Substrate
Authors: Sho Shirakata Sho Shirakata , Shinji Yudate Shinji Yudate , Tomoaki Terasako Tomoaki Terasako , Shigehiro Isomura Shigehiro Isomura
Published: October 2002

The metalorganic molecular beam epitaxial growth of CuInSe2 layers on a GaAs(100) substrate was performed at 550°C using cyclopentadienylcoppertriethylphosphine (CpCuTEP), triethylindium and selenium as source precursors. CuInSe2 layers with a flat surface were successfully grown. The epilayers were examined by X-ray diffraction, photoluminescence (PL) and photoreflectance measurements. The CuInSe2 layer grown under optimum conditions exhibited an exciton emission in the PL spectrum.
Optical Near-Field Imaging Using the Kelvin Probe Technique
Authors: Masayuki Abe Masayuki Abe , Yasuhiro Sugawara Yasuhiro Sugawara , Kazuyoshi Sawada Kazuyoshi Sawada , Yoshitake Andoh Yoshitake Andoh , Seizo Morita Seizo Morita
Published: October 2002

In the force detection of the evanescent field using a semiconductor tip, the force gradient is affected not only by the surface potential change due to the evanescent field, but also by the contact potential difference (CPD) between the tip and the sample which is not uniform on the surface. In this paper, we propose a novel method to measure the evanescent field without the CPD effect using the Kelvin probe technique. Simultaneous images of the topography, the CPD and the force gradient due to the evanescent field were obtained on a 15-nm thickness sputtered Au surface. These images showed no correlation in several areas. The lateral resolution of the force gradient due to the evanescent field was better than 15 nm (λ/33).
Selective Area Growth of Si on Thin Insulating Layers for Nanostructure Fabrication
Authors: Hwang Doo-Sup , Yasuda Tetsuji , Ikuta Kazuyuki , Yamasaki Satoshi , Tanaka Kazunobu
Published: October 2002

A new method of fabricating Si microstructures on thin insulating films is described. It
combines selective-area growth of Si with electron-beam direct patterning of a SiO2/SiN
x
bilayer
mask. The chemical composition of the top SiO2 layer of the mask can be modified locally by
electron-beam irradiation. The different chemical properties between irradiated and nonirradiated
surfaces make it possible to deposit Si only on the irradiated surface. The bottom SiN
x
layer is
stable against electron-beam irradiation, and thus insulates electrically the deposited Si
microstructure from the Si substrate. Selective-area growth of Si was performed by
ultrahigh-vacuum chemical vapor deposition (UHVCVD).
Hybrid Sol–Gel Micro-Patterning of Organic Electroluminescent Devices
Authors: Rantala Juha T. , Jabbour Ghassan E. , Vähäkangas Jouko , Honkanen Seppo , Kippelen Bernard , Peyghambarian Nasser
Published: October 2002

We demonstrate a novel technique of fabricating organic light-emitting devices. Each device consists of 1480 micro-pixels, with a pixel dimension of 45×45 µm2. The pixels were obtained by
using a single-step UV patternable sol–gel hybrid glass thin film. Due to higher fields, micro-pixels based devices show forward light output at lower voltage than
conventional dvices. More than 1% in external quantum efficiency and green light exceeding 27,000 cd/m2 are demonstrated.
Growth of GaN by Atomic Hydrogen-Assisted Molecular Beam Epitaxy
Authors: Hashiguchi Yoshihiro Okamoto , Okada Yoshitaka , Mitsuo Kawabe Mitsuo Kawabe
Published: October 2002

We have studied the effects of atomic hydrogen(H) generated
by a hot tungsten (W) cracking cell upon substrate cleaning
and GaN growth by RF-MBE. And we have shown atomic H
irradiation during thermal cleaning stage produce a smooth
surface, which in turn improves that quality of GaN films.
Also confirmed is that atomic H irradiation during GaN growth
is efficient to improve the crystal quality. Compared to
the PL data of as-grown samples, the annealed samples didn't show
degradation of optical quality. From these, it can be
considered that the possibility of hydrogen passivation is small.
We consider that atomic H irradiation in N-rich GaN growth suppresses
3-D growth and enhances 2-D growth, though the atomic-scale mechanisms
and interaction of atomic H irradiation on GaN growth is not totally
clear at present.
Atomic-Structure-Dependent Adsorption of Ammonia onto GaAs(111)B Surfaces
Authors: Sugawara Shigeru , Sasaki Masahiro , Yamamoto Shigehiko
Published: October 2002

Adsorption of ammonia, which is the initial stage of the vapor phase epitaxial growth of nitride semiconductors, is examined by using pulsed-ammonia-beam scatterings from differently reconstructed
GaAs(111)B surfaces. It is found that the surface atomic structure of GaAs(111)B surface more strongly influences the ammonia adsorption than that of GaAs(100) surface.
Incident ammonia molecules are temporarily trapped in a deep precusor state on a (√ 19×√ 19)R23.4° surface, while they are desorbed without such a surface trapping from an As-excess (2×2) surface.
On the other hand, ammonia is efficiently stuck on a Ga-rich (1×1) surface, which is probably related to the efficient surface decomposition of ammonia under a
specific condition of nitride epitaxy. The results are discussed on the basis of the atomic arrangement of the reconstructed surface.
Stacking and Optical Properties of Layered In 2Se 3
Authors: Masato Ishikawa Masato Ishikawa , Takashi Nakayama Takashi Nakayama
Published: October 2002

Electronic structures and optical properties of layered In2Se3 with various stackings have been studied using ab initio calculation. It is found that since the dangling-bond states of layer-edge Se atoms appear at the top of the valence band, the absorption around the fundamental band gap becomes large for light polarization along the layer direction. This property is common to all stackings and explains well the results of a recent experiment.
Transmission Electron Microscopic Studies of YbBa2Cu3O7-δ-Precursor Films Formed on SrTiO3 by Dipping-Pyrolysis Process
Authors: Shibata Junko , Yamagiwa Katsuya , Hirabayashi Izumi , Hirayama Tsukasa
Published: October 2002

We prepared precursor films of YbBa2Cu3O7-δ by coating SrTiO3(001) single crystal substrate with metalorganic compounds solution and by heating at 425°C. Then, microstructures of the precursor films were observed by
transmission electron microscopy. The film heated rapidly up to 425°C was amorphous. On the other hand, the film heated gradually was polycrystalline. After final annealing at 725°C, the former sample showed a sharp transition of the electric
resistance around critical temperature (T
C). The latter one showed a broad transition. Therefore, we conclude that a high heating rate at the pre-treatment is important for achieving a sharp resistive transition of the final film.
Nitridation of Silicon Oxide Surfaces by Fluorination and Subsequent Exposure to Atomic Nitrogen
Authors: Yoji Saito Yoji Saito , Ukyo Mori Ukyo Mori
Published: October 2002

Nitrogen incorporation into oxide surfaces is required to prevent the penetration of boron from the polycrystalline silicon gate to the substrate in metal-oxide-semiconductor devices. We incorporate nitrogen only into the oxide surfaces by fluorination at room temperature and a subsequent atomic nitrogen treatment at temperatures below 550°C. Incorporated nitrogen atoms are found to be bound to silicon atoms and oxygen atoms by X-ray photoelectron spectroscopy. Moreover, surface roughness is improved by the nitridation process. The proposed technique is a unique process to obtain high-quality ultrathin dielectrics.
Nitrogen Doping Effects on Electrical Properties of Diamond Films
Authors: Jiang Nan , Hatta Akimitsu , Ito Toshimichi
Published: October 2002

Chemical-vapor-deposited (CVD) diamond films with intentional nitrogen doping have
been characterized by various standard techniques. Electrical resistance measurements
demonstrate that the nitrogen doping significantly varies the surface conductivity of as-grown
diamond films; the surface resistance of N-doped diamond films can reach as high as 1011 Ω,
which is about six orders of magnitude higher than that of an undoped one. Such high
surface resistance remains stable even after 8 hours of exposure to hydrogen plasma. It is
also found that the photoemission threshold energy of N-doped diamond films is about
0.55 eV less than the diamond band-gap energy, which implies the existence of compensated
surface gap states and possibly, negative electron affinity in the as-grown N-doped diamond
films. The particular properties observed in the N-doped diamond films are discussed in
relation to the fabrication of diode-type diamond electron emitters.
Spectral Narrowing of Photoluminescence in Conducting Polymer and Fluorescent Dyes Infiltrated in Photonic Crystal, Synthetic Opal
Authors: Katsumi Yoshino Katsumi Yoshino , Satoshi Tatsuhara Satoshi Tatsuhara , Yoshiaki Kawagishi Yoshiaki Kawagishi , Masanori Ozaki Masanori Ozaki , Anvar A. Zakhidov Anvar A. Zakhidov , Z. Valy Vardeny Z. Valy Vardeny
Published: October 2002

Spectral narrowing of photoluminescence (PL) has been observed in conducting polymers such as poly(2,5-dialkoxy- p-phenylenevinylene) infiltrated in photonic crystals, synthetic opals, upon light excitation. Such spectral narrowing has also been observed in synthetic opals infiltrated with fluorescent dyes such as Rhodamine 6G and Coumarin. The threshold of the spectral narrowing in conducting polymers and dyes infiltrated in opal is much lower than that in their solutions. Dependence of spectral narrowing characteristics on the lattice periodicity of opals has also been studied. The results are discussed in terms of amplified spontaneous emission and lasing due to optical feedback in opal.