bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Mechanical Vibration on Patterning Characteristics in Synchrotron Radiation Lithography
Authors: Fukuda Makoto , Endo Naoe , Tsuyuzaki Haruo , Masanori Suzuki Masanori Suzuki , Kimiyoshi Deguchi Kimiyoshi Deguchi
Published: October 2002

In order to improve pattern precision and overlay accuracy in synchrotron radiation (SR) X-ray lithography, it is required that a stepper be very stable mechanically and have a high positioning accuracy with regard to both the mask-to-wafer gap and the stage. It is important to clarify the effect of mechanical vibrations on patterning characteristics. We investigated the effect of mechanical vibrations on line-and-space patterns with dimensions of less than 0.2 µ m by carrying out exposure experiments and patterning simulations. Strong vibrations generally increase the line width, thereby reducing the dose margin. The amplitude of the vibrations should be kept at less than a quarter of the minimum feature size in order to prevent reduction of the dose margin. Furthermore, we developed a simple method of calculating resist pattern profiles from the intensity profile, the thickness of the remaining resist, and the electron scattering depth. The change in line width obtained in this way was almost the same as the measured change.
Diagnostics of Fluorocarbon Radicals in a Large-area Permanent Magnet Electron Cyclotron Resonance Etching Plasma
Authors: Den Shoji , Kuno Tatsushi , Ito Masafumi , Hori Masaru , Goto Toshio , Hayashi Yuzo , Sakamoto Yuichi
Published: October 2002

Diagnostics of fluorocarbon radicals and fluorine (F) atom species in a size-scaleable large-area permanent magnet electron cyclotron resonance (ECR) etching plasma employing CF4 and C4F8 gases are carried out. Non-intrusive infrared laser diode absorption spectroscopy and actinometric measurement techniques are used in evaluating the performance of the permanent magnet ECR plasma source and in studying the kinetic processes associated with etching plasma chemistry. Successful measurements of the absolute CF and CF2 radical and F atom densities have been achieved. In particular for C4F8 plasma, enhanced CF and CF2 radical densities which afford higher selectivity in the etching of SiO2 on Si are discussed. At a pressure of 0.4 Pa and an input microwave power of 900 W the CF and CF2 radical and F atom densities in C4F8 plasma were 1.7×1013 cm-3, 6.0×1013 cm-3 and 1.5×1013 cm-3, respectively. These results are also discussed in comparison with results for a conventional electromagnet ECR plasma source.
Reduction of Selectivity Loss Probability on Dielectric Surface during Chemical Vapor Deposition of Tungsten Using Fluorinated Oxide and Removing Silanol Units on Dielectric Surface
Authors: Chang Kow Ming , Wang Shih Wei , Li Chii Horng , Jung Yu Tsai Jung Yu Tsai , Ta Hsun Yeh Ta Hsun Yeh
Published: October 2002

Dielectric materials and surface pretreatment are important for the control of selectivity loss during the chemical vapor deposition (CVD) of W in SiH4/ H2/ WF6 ambient. Water-related silanol (SiOH) units on an oxide surface, which come from a wet cleaning step and moisture in clean room air, are found to act as nucleation centers, resulting in selectivity loss. Removing these silanol units by in situ NF3 plasma pretreatment effectively inhibits the nucleation of W. Reduction of the dielectric constant, as well as doping of fluorine in oxide, was shown to suppress the selectivity loss. This is due to the high electronegativity of the F

x

SiO

y

film surface, which repels the WF6 molecules. The resistance to selectivity loss of W on F

x

SiO

y

is better than that on BPSG. From these results, nucleation of W is inferred to initiate from the adsorption of WF6 on the insulator surface in the WF6/ SiH4/ H2 ambient. On the other hand, a novel method that uses F

x

SiO

y

as an intermetal dielectric (IMD) or that involves capping on a dielectric material ( e.g., BPSG), was proposed to reduce the selectivity loss probability during selective growth processes.
Recent Developments in Electrical Linewidth and Overlay Metrology for Integrated Circuit Fabrication Processes
Authors: Cresswell Michael W. , Sniegowski Jeffry J. , Ghoshtagore Rathindra N. , Allen Richard A. , Guthrie William F. , Gurnell Andrew W. , Linholm Loren W. , Ronald G. Dixson Ronald G. Dixson , E. Clayton Teague E. Clayton Teague
Published: October 2002

Electrical linewidth measurements have been extracted from test structures replicated in planar films of monocrystalline silicon that were electrically insulated from the bulk-silicon substrate by a layer of silicon dioxide formed by separation by the implantation of oxygen (SIMOX) processing. Appropriate selection of the surface orientation of the starting material, the design and orientation of the structure's features, and patterning by a lattice-plane selective etch provide features with planar, atomically smooth sidewalls and rectangular cross sections. The primary motivation for this approach is to attempt to overcome the serious challenge posed by methods divergence to the certification of linewidth reference-materials for critical-dimension (CD) instrument calibration and related tasks. To enhance the physical robustness of reference features with deep submicrometer linewidths, the new test structure embodies short reference-segment lengths and arbitrarily wide voltage taps. Facilities for reconciliation of measurements extracted from the same feature by all normally practiced techniques are also implemented. In overlay metrology, electrical inspection of two types of hybrid overlay targets allows pixel calibration of, and shift extraction from, the overlay instruments. The overall strategic focus of this research is to resolve methods-divergence issues and possibly to develop universal deep-submicrometer linewidth reference materials for CD instruments and techniques for instrument- and process-specific shift extraction for optical overlay metrology.
Fabrication of Field Emitter Arrays with Hydrogenated Amorphous Silicon on Glass
Authors: Gamo Hidenori , Seigo Kanemaru Seigo Kanemaru , Junji Itoh Junji Itoh
Published: October 2002

An n-type hydrogenated amorphous silicon ( n+-a-Si:H) field emitter array (FEA) was fabricated on a glass substrate and characterized. The n+-a-Si:H film was deposited by a conventional plasma-enhanced-chemical-vapor-deposition (PECVD) technique using a silane and phosphine mixed gas at a temperature lower than 350° C. The present film showed a low resistivity of 50 Ω· cm. The FEA consists of 1-µm-high emitter tips and a gate electrode with 1.8-µm-diameter openings. Using the fabricated FEA (25-tips), an emission current of 11 µ A was obtained at a gate voltage of 100 V.
Fabrication of Silicon Field Emitter Arrays Integrated with Beam Focusing Lens
Authors: Yamaoka Yoshikazu , Seigo Kanemaru Seigo Kanemaru , Junji Itoh Junji Itoh
Published: October 2002

A new field emitter structure capable of generating a focused electron beam (FEB) was fabricated. The present structure is basically similar to a double-gated structure, however, the two gate openings are arranged in the same way as a confocal in-plane lens structure. The inner gate acts as an extraction gate with a 0.6-µm-diameter opening and the outer one acts as an electrostatic focusing lens with a 2.4-µm-diameter opening. The field emission characteristics were evaluated and a beam current of 70 nA/tip was obtained when a bias voltage of 70 V was applied to the two gates. The beam focusing characteristics were also evaluated and the beam could be focused by decreasing the focusing lens voltage without a significant decrease in the beam current.
Fabrication of Single-Crystal Si Microstructures by Anodization
Authors: Katsuya Higa Katsuya Higa , Tanemasa Asano Tanemasa Asano
Published: October 2002

We have investigated the application of the anodization process to the fabrication of microstructures consisting of single-crystal Si. When anodization is carried out in the dark, porous Si is preferentially formed in a p-type region. The porous region can be used as a sacrificial region. The unanodized Si region forms the components of the microstructures. The shape of the porous region can be controlled by varying the profiles of the n- and p-type regions and their resistivity. It has been found that, by utilizing these characteristics, various microstructures can be formed from single-crystal Si. Fabrication of a cantilever and a piezoresistive gauge for a pressure sensor are demonstrated.
Electron Beam Induced Current Characterization of Novel GaAs Quantum Nanostructures Based on Potential Modulation of Two-Dimensional Electron Gas by Schottky In-Plane Gates
Authors: Kasai Seiya , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

The electron beam induced current (EBIC) technique was used for characterization of novel GaAs quantum nanostructures based on potential modulation of two-dimensional electron gas (2DEG) by Schottky in-plane gates (IPGs). A simple theory on the EBIC signal from the basic Schottky IPG structure was developed and it was compared to experimental results. Excellent agreement between theoretical and experimental results was obtained, indicating that the EBIC technique is a powerful means to detect electric field profiles in depletion layers of quantum nanostructures. The EBIC technique was also applied to Schottky IPG-based quantum wires, lateral superlattices and multi-quantum dot chains. The EBIC study revealed that effective potential control and electron confinement can be achieved by suitable design of Schottky IPG electrodes.
Inheritance of Crystal Structure in Cu/Co and Co/Cu Bilayers Grown on MgO(100) Substrate
Authors: Masahiko Yamamoto Masahiko Yamamoto , Hiroshi Hayasaki Hiroshi Hayasaki , Kouichi Nishikawa Kouichi Nishikawa , Toshiki Kingetsu Toshiki Kingetsu
Published: October 2002

Bilayers and single layers composed of Co and Cu were formed on MgO(100) substrates as the fundamental unit of the superlattice of Cu and Co. The crystal structure of their films was investigated, with increasing layer thickness of each element, by reflection high-energy electron diffraction observation and X-ray diffraction analysis. If Cu is deposited on MgO(100) first, Cu has the fcc structure and subsequently deposited Co has a metastable fcc structure which is inherited from the crystal structure of the underlying Cu. Cu on hcp-Co has a metastable hcp structure for thin Cu which is inherited from the crystal structure of the underlying Co. The structure of the Cu changes to fcc with increasing Cu layer thickness and the Cu is released from the influence of the substrate.
Study of Quasi-Two-Dimensional Hole Gas in Si/SixGe1-x/Si Quantum Wells
Authors: Sanghoon Cheon Sanghoon Cheon , Seungchang Lee Seungchang Lee , Songcheol Hong Songcheol Hong , Kyeonghwa Yoo Kyeonghwa Yoo
Published: October 2002

Quasi-two-dimensional hole gas in strained Si/SixGe1-x
/Si quantum well structure is investigated both theoretically and experimentally. The hole effective mass and the charge distribution in the structure are obtained from the self-consistent solution of the Schr\ddotodinger-Poisson equations. The calculation results show the dependence of the averaged mass on the measurement temperature and the averaged mass of 0.20 m
0 at T = 4 K. High quality Si/Si0.8Ge0.2/Si p-type modulation-doped quantum well is grown by molecular beam epitaxy and the electrical properties measured. Hall mobility as high as ∼10,400 cm2/V·s with a sheet carrier concentration of ∼1.1 ×1012 cm-2 and an effective mass of ∼0.30 m
0 is obtained at T = 4 K.
A 0.25 µm Complementary Metal Oxide Semiconductor Field Effect Transistor (CMOSFET) using Halo Implantation for 1 Gbit Dynamic Random Access Memory (DRAM)
Authors: Jung Dong Jin , Park Jae Kwan , Lee Kang Yoon , Kang Nam Soo , Kim Ki Nam , Tae Earn Shim Tae Earn Shim , Jong Woo Park Jong Woo Park
Published: October 2002

A 0.25 µm complementary metal oxide semiconductor field effect transistor (CMOSFET) has been developed using halo implantation for 1 Gbit dynamic random access memory (DRAM). This technology features a source/drain implantation followed by a halo implantation with an inclined angle after formation of oxide sidewall spacer. The halo implantation is performed without additional implantation masks. Dopants formed by the halo implantation act as the punchthrough stopper that surrounds the lightly doped drain (LDD) implantation region. As a result, the short-channel effect (SCE) of the halo CMOSFET is dramatically suppressed as compared with that of the conventional CMOSFET and the breakdown voltage between drain and source (BVds) margin is markedly improved more than 0.05 µm for n-channel metal oxide semiconductor field effect transistor (NMOSFET) and 0.12 µm for p-channel metal oxide semiconductor field effect transistor (PMOSFET).
A High-Performance 0.05 µm SOI MOS FET: Possibility of Velocity Overshoot
Authors: Kazuya Ohuchi Kazuya Ohuchi , Ryuji Ohba Ryuji Ohba , Hiromi Niiyama Hiromi Niiyama , Kazuaki Nakajima Kazuaki Nakajima , Tomohisa Mizuno Tomohisa Mizuno
Published: October 2002

A high-transconductance 0.05 µm n-channel metal-oxide-semiconductor field-effect transistor (MOS FET) has been realized using thin silicon on insulator (SOI)/buried oxide structures. The measured and the intrinsic transconductance values are 472 mS/mm and 702 mS/mm, respectively. These are the highest G
m values yet reported for SOI MOS FET. Electron velocity, however, is 82% of the bulk saturation velocity, v
sat. This is mainly due to the degradation of the mobility caused by scattering in the SOI layer and the temperature increment induced by the self-heating effect. Therefore, it is important to achieve both mobility-degradation-free and self-heating-free conditions in order to realize a high-speed SOI MOS FET using the carrier velocity overshoot.
Capacitance Network Model of the Short Channel Effect for 0.1 µm Fully Depleted SOI MOSFET
Authors: Koh Risho , Kato Haruo , Hiroshi Matsumoto Hiroshi Matsumoto
Published: October 2002

We propose a simple analytical model of the short channel effect in a fully depleted silicon-on-insulator metal-oxide-silicon field effect transistor (SOI-MOSFET). The influence of the two-dimensional effect on the potential distribution, the threshold voltage and the S factor are evaluated based on the spatial distribution of the characteristic capacitances between the SOI body and each electrode (gate, source, drain and substrate). This treatment makes it possible to estimate the two-dimensional effect without solving Poisson's equation which requires a large computation time. This model describes the short channel effect down to the 0.1 µm regime.
Initial Growth Processes of ZnSe on Cleaned GaAs(001) Surfaces by Metalorganic Vapor Phase Epitaxy
Authors: Katsuhiro Uesugi Katsuhiro Uesugi , Hideki Suzuki Hideki Suzuki , Hiroyuki Nashiki Hiroyuki Nashiki , Toshio Obinata Toshio Obinata , Hidekazu Kumano Hidekazu Kumano , Ikuo Suemune Ikuo Suemune
Published: October 2002

The effect of organic As flow during the thermal cleaning of GaAs substrates in metalorganic vapor phase epitaxy (MOVPE) and the initial growth of ZnSe on the cleaned GaAs surfaces are investigated using atomic force microscopy, X-ray diffraction and photoluminescence measurements. The thermal cleaning with organic As flow in MOVPE is effective to form atomically flat GaAs surfaces and to grow high-quality ZnSe films. The initial growth processes of ZnSe films are critically dependent on the GaAs surface and on the VI/II flow ratio for the ZnSe growth. The initial growth process of ZnSe films on GaAs surfaces is dominated by the two-dimensional growth mode for Zn-rich growth conditions, while three-dimensional island growth becomes dominant as the Se flow rate increases.
Lower-Temperature Growth of Hydrogenated Amorphous Silicon Films from Inductively Coupled Silane Plasma
Authors: Masashi Goto Masashi Goto , Hirotaka Toyoda Hirotaka Toyoda , Masatoshi Kitagawa Masatoshi Kitagawa , Takashi Hirao Takashi Hirao , Hideo Sugai Hideo Sugai
Published: October 2002

A high-density (1011 cm-3) inductively coupled plasma at low pressure (0.1 Pa) of SiH4 enables the growth of hydrogenated amorphous silicon films of high photoconductivity (10-5 S/cm) at substrate temperatures ( <100 °C) considerably lower than that with a conventional capacitive rf plasma. Such low-pressure high-power discharges were achieved by inserting a loop antenna into a plasma with magnetic multipole confinement. Thus, this type of rf reactor appears to be promising to realize high-speed deposition of large-area a-Si:H films at room temperature.
A Theoretical Investigation of the Epitaxial Relationship of NiAl/AlAs
Authors: Tomonori Ito Tomonori Ito
Published: October 2002

The epitaxial relationship between NiAl and AlAs is investigated theoretically, using cohesive energy calculations based on empirical interatomic potentials. We consider various systems such as NiAl(001) on AlAs(001), and AlAs(001) and AlAs(111) on NiAl(001) with interface atom pairs including As/Ni, Al/Ni, As/Al and Al/Al. The calculated results for NiAl(001) on AlAs(001) imply that the formation of a Ni atomic layer at the interface can stabilize NiAl(001). In AlAs on NiAl(001), Al/Ni and As/Ni interfaces favor AlAs(001), whereas AlAs(111) is relatively stable in As/Al and Al/Al interfaces. These findings are qualitatively consistent with experimental results.
Effect of Hydrogen-Radical Annealing for SiO2 Passivation
Authors: Nagayoshi Hiroshi , Onozawa Yuichi , Ikeda Makoto , Yamaguchi Misako , Yamamoto Yuichi , Uematsu Tsuyoshi , Tadashi Saitoh Tadashi Saitoh , Koichi Kamisako Koichi Kamisako
Published: October 2002

It is shown that hydrogen-radical postannealing of SiO2 on Si wafers can result in high effective lifetime (τ eff), low surface recombination velocity (S
eff) and low midgap interface state density at the SiO2/Si interface (D
ito). The annealing effect appeared above 200° C within a very short annealing time to a greater degree than in 3% H2 forming gas annealing at 400° C. This annealing method is suitable for the surface passivation process of solar cell devices.
Hydrogenation Time Dependence of a-SiC:H-Based P-I-N Thin Film Visible Light-Emitting Diode Characteristics
Authors: Jong-Wook Lee Jong-Wook Lee , Koeng Su Lim Koeng Su Lim
Published: October 2002

The hydrogenation time dependence of hydrogenation effects on the performance of a-SiC:H-based p-i-n thin film light-emitting diodes (TFLEDs) in the visible range has been investigated. It was found that hydrogenation markedly improved the device performance, and that increasing the hydrogenation time beyond a saturation point degraded the device performance; that is, as compared with the performance of a TFLED hydrogenated for a short time (∼15 min), the threshold voltage increased slightly, the EL peak shifted towards a longer wavelength, and the brightness decreased. In particular, after hydrogenation for 45 min, the brightness decreased to 15 cd/m2.
Time Dependence of Impedance Characteristic of Nematic Liquid Crystal Cell
Authors: Mada Hitoshi , Ohnoya Satoru , Endoh Hideyuki , Fukuro Hiroyoshi
Published: October 2002

The frequency dependence of the impedance of a liquid crystal cell was measured for 4-n-pentyl-4′-cyanobiphenyl. The resistivity of a liquid crystal layer decreases due to two relaxation processes. The relaxation time for the slow process is about 4000 h, and that for the fast process is of the order of 100 h. This implies that the carrier ion concentration increases over a long period of time. A surface double layer was detected at the polyimide in the low frequency region, the thickness of which tends to decrease with time.
Excimer-Type Electroluminescence and Carrier-Transporting Properties of Electron-Accepting π-Conjugated Polymers
Authors: Yamamoto Takakazu , Suganuma Hajime , Saitoh Yutaka , Tsukasa Maruyama Tsukasa Maruyama , Tetsushi Inoue Tetsushi Inoue
Published: October 2002

Rigidly linear and electron-accepting π-conjugated polymers such as poly(pyridine-2,5-diyl), poly(1,10- phenanthroline-3,8-diyl), and poly(4,4′-disubstituted-2,2′-bithiazole-5,5′-diyl) serve as carrier-transporting and light-emitting materials in electroluminescence devices, and they show emission of light which is considered to originate from excimer-type adducts.
Carrier Concentration Saturation of Double Si Doping Layers in GaAs
Authors: Zhongling Peng Zhongling Peng , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

Doubly Si δ-doped GaAs samples with different spacer thickness are grown by molecular beam epitaxy. By adopting a growth temperature as low as 400° C, a “true” δ-doping profile is realized and confirmed by Shubnikov-de Haas measurement. A depopulation of sheet carrier concentration is observed as the two layers approach each other. The carrier concentration saturates in such a way that the depth of the self-consistently calculated Hartree potential is kept constant at around 235 meV. Since carrier concentration saturation due to structural reasons remains unchanged in these structures, the pinning of Fermi level suggests a dominant electronic saturation mechanism most likely through the population of DX center states.
Electrically Isolated Metal-Semiconductor Field Effect Transistors and Logic Circuits on Homoepitaxial Diamonds
Authors: Kawarada Hiroshi , Masahiro Itoh Masahiro Itoh , Akira Hokazono Akira Hokazono
Published: October 2002

Isolated metal-semiconductor field effect transistors (MESFETs) have been fabricated on homoepitaxial diamonds grown by microwave plasma chemical vapor deposition. Source, drain and channel regions are fabricated using the surface p-type semiconductive layer unique to hydrogen-terminated diamond surfaces. Other areas are irradiated by an argon beam to obtain highly resistive regions. The maximum transconductance of the isolated MESFETs with 7 µ m gate length is 4.5 mS/mm, which is comparable to that of silicon MOSFET with the same gate length. NOT, NAND, NOR, and R-S flip-flop circuits have been fabricated for the first time on diamond using enhancement-mode active loads.
Distribution of Fe in an Intrinsic Gettered Silicon Wafer after Annealing at Supersaturation Temperature
Authors: Masaki Aoki Masaki Aoki , Akito Hara Akito Hara
Published: October 2002

We studied the distribution of Fe in thermal equilibrium after annealing at supersaturation temperature. Analyses by deep-level transient spectroscopy (DLTS) showed that the Fe concentrations in the denuded zone and in the bulk region of a Czochralski (CZ) intrinsic gettered wafer are the same when depletion of Fe from the denuded zone stops. This Fe concentration corresponds to the solid solubility of Fe in the wafer at the annealing temperature used. This result indicates that there is no difference in Fe solid solubility between the bulk region and the denuded zone of the wafer. Results of transmission electron microscopy (TEM)-energy dispersive X-ray (EDX) analyses suggest that supersaturated Fe in an intrinsic gettered wafer precipitates preferentially with oxygen precipitates in the bulk region, while supersaturated Fe in an as-grown wafer precipitates in the near-surface region.
Perpendicular Magnetization of Epitaxial FePt(001) Thin Films with High Squareness and High Coercive Force
Authors: Homma Masato Watanabe
Published: October 2002

Perpendicular magnetized epitaxial FePt(001) thin films were prepared by RF-magnetron sputtering. The long range order parameter S of the FePt layer was found to be ∼0.9. Very narrow X-ray rocking curves ( FWHM<1°) of the FePt(002) and Pt(200) peaks indicate that both layers are essentially single crystalline. With increasing Pt buffer layer thickness d
Pt, the squareness M
r/M
S and coercive force H
C were found to increase to 100% and 7.2 kOe, respectively. The FePt(001) thin film has a |0.58°| peak at a photon energy of 2.0 eV (630 nm wavelength) in the polar magnetooptical Kerr rotation θ K spectrum, which does not agree with that of the polycrystalline FePt ordered alloy.
A Stabilization Mechanism for Optical Parametric Frequency Division Based on Insertion of a Second-Harmonic-Generation Element
Authors: Zheng Qianbing , Lei Zhang Lei Zhang , Takayoshi Kobayashi Takayoshi Kobayashi
Published: October 2002

A stabilization mechanism for optical parametric frequency division using intracavity second harmonic generation (SHG) is proposed. When the optical parametric oscillation is continuously tuned around the point of exact 3:2:1 pump:idler:signal frequency division, a resonant seeding from the idler wave significantly enhances the intracavity SHG which is designed to double the signal wave. As a result, the power output versus frequency of the signal wave follows a curve which exhibits a dip centered at the point of exact division, and techniques can be devised to use the shape of the curve for the purpose of stabilizing the optical frequency division.
Generation of Ultrashort (∼ 65 fs) Pulses from 1.55 µ m Gain-Switched Distributed Feedback (DFB) Laser with Soliton Compression by Dispersion Arrangements
Authors: Masanao Miyamoto Masanao Miyamoto , Masahiro Tsuchiya Masahiro Tsuchiya , Hai-Feng Liu Hai-Feng Liu , Takeshi Kamiya Takeshi Kamiya
Published: October 2002

We report the successful generation of optical pulses (∼ 65 fs) from a 1.55 µm gain-switched distributed feedback semiconductor laser with fiber optic compression techniques by a novel dispersion arrangement. These pulses are the shortest ever generated starting from a semiconductor laser diode and are promising for practical applications in ultrafast photonic systems.
White-Light-Emitting Material for Organic Electroluminescent Devices
Authors: Hamada Yuji , Sano Takeshi , Fujii Hiroyuki , Nishio Yoshitaka , Hisakazu Takahashi Hisakazu Takahashi , Kenichi Shibata Kenichi Shibata
Published: October 2002

White emission is important for applying organic EL devices to full-color displays and backlighting. In order to obtain white emission, the use of a white-light-emitting material which shows the white emission by itself is advantageous for these applications because of its high reliability and productivity. A device structure of indium-tin-oxide (ITO, anode)/hole transport layer/emitting layer/MgIn alloy (cathode) was employed. Bis(2-(2-hydroxyphenyl)benzothiazolate)zinc ( Zn(BTZ)2) was used as the emitting material. Zn(BTZ)2 showed greenish-white emission with a broad electroluminescent spectrum (half-width: 157 nm, peak wavelength: 486, 524 nm). It exhibited a high luminance of 10,190 cd/m2 at the applied voltage of 8 V because Zn(BTZ)2 has a good electron-transport property. As such, Zn(BTZ)2 is expected to serve as a new white-light-emitting material for organic EL devices.
Growth of InN by Chloride-Transport Vapor Phase Epitaxy
Authors: Sunakawa Haruo , Yamaguchi A. Atsushi , Kimura Akitaka , Akira Usui Akira Usui
Published: October 2002

Hexagonal single crystalline InN film are grown on a hexagonal-GaN epitaxial layer in a GaAs(100) substrates by chloride-transport vapor phase epitaxy. It is found that lower temperatures for the upstream region of the reator, where indium chloride is generated, are crucial for InN growth. In addition, the use of inert gas such as nitrogen, is necessary for growth. Based on these results, the necessity of InCl3 as a source material is emphasized for InN growth. The grown film reveals a hexagonal structure whose c-axis orients to the GaAs<111>B direction.
Improvement in Parameter Spreads of YBaCuO/PrBaCuO/YBaCuO Trilayer Junctions
Authors: Sato Hiroshi , Nakamura Norito , Stein Roar Gjøen Stein Roar Gjøen , Hiroshi Akoh Hiroshi Akoh
Published: October 2002

An improvement in the distribution of junction properties for YBaCuO/PrBaCuO/YBaCuO trilayer junctions has been demonstrated. In order to ensure a uniform substrate temperature during the deposition of trilayer films, Al/Cu/Al stacked foils are introduced as a backing plate between the substrate and sample holder. Furthermore, the film composition is optimized to reduce the precipitated particles on the surface of the films. All the junctions with a barrier thickness of 35 nm and an area less than 100 µ m2 show RSJ-like current voltage characteristics with some excess current at 4.2 K. The 1-σ spreads of Josephson critical current density J
c and normalized junction resistance R
n
A are obtained to be 34% and 25%, respectively, for 88 junctions on the same substrate. This result is comparable to the 1-σ spreads of ramp-edge type junctions.
Room Temperature Ultraviolet Electroluminescence from Evaporated Poly(dimethylsilane) Film
Authors: Reiji Hattori Reiji Hattori , Takeshi Sugano Takeshi Sugano , Junji Shirafuji Junji Shirafuji , Tsuyoshi Fujiki Tsuyoshi Fujiki
Published: October 2002

Ultraviolet electroluminescent diodes operating at room temperature have been prepared using evaporated poly(dimethylsilane) (PDMS) as an emission layer. The emission spectrum is composed of ultraviolet and visible components. The ultraviolet component peakes at 350 nm due to the σ–σ* transition in the Si main chain while the visible region is broad and may be related to defects in the PDMS film. Little degradation is observed in the emission characteristics. The external quantum efficiency is estimated to be as low as 1.6×10-4 because of the absorption loss of the glass substrate and for other reasons.
Thermal Fatigue Life Prediction of Gull-Wing Solder Joints in Plastic Thin Small Outline Packages
Authors: Seong-Min Lee Seong-Min Lee , Kwon-Woo Lee Kwon-Woo Lee
Published: October 2002

A nonlinear, time-dependent finite element modeling analysis has been performed to determine the strain distribution in gull-wing solder joints and to predict the fatigue life of the plastic thin small outline package (TSOP). The life prediction was done based on the modified Coffin-Manson law where the fatigue life of solder joints subjected to thermal cycling was estimated as a function of the creep strain. Strain-based solder life prediction was first performed to assess the effect of lead material selection, indicating that a ductile lead considerably enhances solder fatigue life. Moreover, numerical calculation also demonstrates how matching the coefficient of thermal expansion of the plastic component and the printed circuit board (PCB) to the reduction of the chip thickness, influences solder joint reliability.
Low-Power Pulsed-Laser Annealing of the Damaged Surface Layer of Chemomechanically Polished CdS
Authors: Vitali Gianfranco , Pizzuto Cesare , Zollo Giuseppe , Lucca Don A. , Luca Luigi De
Published: October 2002

We report on the laser-induced recrystallization of the shallow surface disorder in a CdS sample during chemomechanical polishing. The role of the incident photon energy, with respect to the band gap energy of CdS, in the lattice structural evolution during irradiation has been determined. Our results indicate that a disordered-to-monocrystalline phase transition, without surface damage, occurs when low-power pulsed-laser annealing (LPPLA) is performed with a laser photon energy higher than the band gap energy of CdS.
Structural and Magnetic Properties of Ni–O/Ni–Fe Bilayer Films
Authors: Ohshima Norikazu , Masafumi Nakada Masafumi Nakada , Yuji Tsukamoto Yuji Tsukamoto
Published: October 2002

Investigations on the relationship between the magnetic properties and structure of Ni–O/Ni–Fe bilayer sputtered films were conducted. The Ni–O/Ni–Fe films were prepared under various Ar gas pressures during Ni–O layer deposition and various distances between targets and substrates. The exchange coupling field decreased as the Ar gas pressure was increased, although the coercive force remained constant. The distance between the target and the substrate does not affect the magnetic properties. Structural analysis revealed that the Ni–O layer exhibits a rhombohedral structure distorted in the direction of <111> from the cubic NaCl structure. The interaxial angle α, which is the angle between two crystallographic axes in the rhombohedral unit cell, gradually decreases as the Ar gas pressure increases until finally the cubic NaCl structure is formed. We found that there is a linear relationship between the values of the exchange coupling field and α which corresponds to the degree of distortion from the NaCl structure. It is considered that the structural distortion of the Ni–O layer affects its antiferromagnetic state, then the exchange coupling between Ni–O and Ni–Fe layers is affected as a result.
Cell Thickness-Induced Ferrielectric Phases in Antiferroelectric/Ferrielectric Liquid Crystals
Authors: Li Jian-Feng , Shack Elizabeth A. , Yu Yi-Kuo , Wang Xin-Yi , Rosenblatt Charles , Neubert Mary E. , Keast Sandra S. , Gleeson Helen
Published: October 2002

The ferrielectric subphases of the liquid crystal MHPOBC [4-(1-methylheptyloxy-carbonyl) phenyl 4′-octyloxy- biphenyl 4-carboxylate] were examined by an optical retardation technique as functions of temperature, applied electric field, and cell thickness. We found that thinner cells exhibit more field-induced ferrielectric steps than do thicker cells. This appears to be a universal phenomenon for all ferrielectric subphases.
Large Grain Growth in Cu(In, Ga)Se 2 Thin Films with Band Gap of around 1.4 eV by Thermal Crystallization in Saturated Se Vapors
Authors: Yamaguchi Toshiyuki , Yamamoto Yukio , Tanaka Tooru , Demizu Yasutaka , Yoshida Akira
Published: October 2002

Thin films of Cu(In, Ga)Se2 were prepared by thermal crystallization in saturated Se vapors from a precursor which was evaporated from Cu(In, Ga)Se2 compound without substrate heating. These thin films had a single phase with chalcopyrite structure. By scanning electron microscopy, large grain growth in Cu(In, Ga)Se2 thin films crystallized in saturated Se vapors was observed in comparison with that in samples prepared without Se shots. Grain sizes of more than 1 µm were obtained with uniform distribution in Cu(In, Ga)Se2 thin films crystallized in saturated Se vapors. The Hall mobility was increased and a band gap of around 1.4 eV was obtained for Cu(In, Ga)Se2 thin films crystallized in saturated Se vapors. This value of band gap lies in the optimum range for solar energy conversion theoretically.
Chemical Etching Failure of SiO 2 Film
Authors: Masaaki Shimizu Masaaki Shimizu , Hiroaki Iwakuro Hiroaki Iwakuro
Published: October 2002

A failure in which a SiO2 film on a Si wafer was not etched completely in a buffered hydrogen fluoride solution occurred. This etching failure is likely to occur when a photoresist is coated thicker than about 2 µm on the SiO2 film. Also, etching failure occurred even in broad mask patterns such as 100×1000 µm2 ones. The etching failure decreased with an increase in the wettability of the photoresist surface. In addition, a buffered hydrogen fluoride solution including surfactants decreased the etching failure. This etching failure is attributed to an air bubble formed at the contact hole when a wafer is immersed into the etching solution.
GaAs-Based Vertical-Cavity Surface-Emitting Laser on Si Substrate by Metalorganic Chemical Vapor Deposition
Authors: Yoshihiko Murata Yoshihiko Murata , Naoki Nakanishi Naoki Nakanishi , Takashi Egawa Takashi Egawa , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: October 2002

We have fabricated an AlGaAs/GaAs surface emitting laser on a Si substrate by metalorganic chemical vapor deposition. A distributed Bragg reflector consisting of 23 periods of AlAs/Al0.1Ga0.9As semiconductor multilayers and a Au metal thin-film reflector are used as reflection mirrors of the Si substrate side and of the top side, respectively. The laser has a cavity which is three times as long as the lasing wavelength and has an Al0.3Ga0.7As/GaAs multi (10) quantum well structure. This laser exhibits a cw threshold current of 73 mA (3.7 kA/cm2) at 100 K. In addition, the lasing wavelength is 844 nm with a full width at half-maximum of 2.2 nm. To our knowledge, this surface emitting laser on Si is the first to be operated under cw conditions.
Gas Source Molecular Beam Epitaxial Growth of GaN 1-xPx (x \Leq 0.015) Using Ion-Removed Electron Cyclotron Resonance Radical Cell
Authors: Iwata Kakuya , Asahi Hajime , Kumiko Asami Kumiko Asami , Shun-ichi Gonda Shun-ichi Gonda
Published: October 2002

The GaN-rich side of GaN1-x
P
x
alloy exhibits a potentially large variation in band-gap energy with P content due to its large bowing. GaN1-x
P
x
layers are grown on (0001) sapphire substrates by electron cyclotron resonance molecular beam epitaxy (ECR-MBE) using an ion-removed ECR radical cell after the growth of high-quality GaN layers. During the growth of the high-quality GaN layers, ×2 reflection high-energy electron diffraction (RHEED) patterns are observed. During the growth of the GaN1-x
P
x
layers, RHEED pattern exhibits a ×1 streak. The near band edge excitonic photoluminescence (PL) peak from the GaN-rich side of the GaN1-x
P
x
layers shows a large red shift with change in P content. A P content of as large as x=0.015 is obtained. However, at x=0.015 phase separation into GaN-rich GaN1-x
P
x
and GaP-rich GaP1-y
N
y
is observed.
Improved Morphology and Surface Resistance of EuBa 2Cu 3O 7-δ Thin Films on MgO Substrates Obtained by Intermittent Magnetron Sputter Deposition
Authors: Koji Tsuru Koji Tsuru , Shin-ichi Karimoto Shin-ichi Karimoto , Shugo Kubo Shugo Kubo , Minoru Suzuki Minoru Suzuki
Published: October 2002

We demonstrate that the surface morphology of off-center magnetron sputtered EuBa2Cu3O7-δ (EBCO) thin films on MgO (100) substrates is improved significantly by using the intermittent deposition method. This method comprises three steps. First, an initial EBCO layer, 2 to 10 unit cell layers thick, is grown at 630–660°C under a low oxygen partial pressure of 0.1 Pa. Then the initial layer is in situ annealed for 30 min under the same conditions used for the deposition. Finally, another EBCO layer is grown on top of the first layer. An EBCO thin film grown in this way has an extremely smooth surface and the surface resistance at 50 GHz is 3 mΩ or less at 77 K, which compares with the best value ever reported.
Large Faraday Effect in Bi 2O 3-Based Glasses
Authors: Qiu Jianrong , Hirao Kazuyuki
Published: October 2002

Bi2O3-based glasses have been prepared. The wavelength dispersions of the Faraday effect for the glasses have been examined. The glasses have a positive Verdet constant for wavelengths from 550 to 850 nm. The Verdet constant of the glasses decreases with increasing wavelength, and increases with increasing concentration of Bi3+ ions. The Verdet constants of glass with a composition of 70Bi2O3·20ZnO·10Li2O (mol%) reach 0.18 min·cm-1·Oe-1 at 700 nm and 0.23 min·cm-1·Oe-1 at 633 nm, which, to our knowledge, are the largest observed in oxide glasses. These glasses may be promising materials for magneto-optical applications.
Measurements of the Time-Averaged Sheath Drop Using the Gridded Energy Analyzer
Authors: Sugawara Kazumasa Sando
Published: October 2002

The time-averaged sheath drops across the sheath in front of a powered electrode have been determined using the gridded energy analyzer, by estimating the maximum energy of the ions accelerated by the sheath potential. It is observed that from pressure p=0.01 to 1 Torr, the sheath drops decrease slightly with operating pressure, and above p=0.1 Torr, the sheath drops exhibit a sharper decrease. Also, the sheath drops increase sharply with R.F. power input. These results could be explained qualitatively in terms of the variation of R.F. voltage amplitude with pressure and R.F. power.
Synchrotron Radiation Micromachining of Polymers to Produce High-Aspect-Ratio Microparts
Authors: Yanping Zhang Yanping Zhang , Takanori Katoh Takanori Katoh
Published: October 2002

Synchrotron radiation (SR) direct micromachining of polymers was developed and high-aspect-ratio microparts of polytetrafluoroethylene (PTFE) were made. The limitation of critical dependence on the photon flux was eliminated by processing PTFE at a temperature of 200–250°C, so that the process was greatly simplified and the aspect-ratios were improved with reducing the smallest surface detail to less than ten microns and achieving the largest structural height of one thousand microns. The decomposition mechanism was discussed with a comparison between the SR micromachining and laser ablation.
Oxygenation and Critical-Temperature Optimization in M-1212 Cuprates (Sr, Ba)2YCu2.8M0.2Oz (M=Ti, Ga, Ge, Al)
Authors: Akira Ono Akira Ono
Published: October 2002

Correlations among oxygen content (z), critical temperature (T
c) and lattice parameters were studied for M-1212 cuprates prepared at high oxygen pressures. T
c increases linearly with increasing average formal Cu valence (p
′) and a maximum T
c is realized above a critical p
′ value ranging from 2.34 to 2.41 which depends on the kind of M cation. Assuming a parabolic relationship between T
c and hole density in the CuO2 sheet (p
s), the high critical p
′ values suggest extraordinarily high hole densities in the CuO planes (p
c). The conclusion is discussed in view of the structures of Cr-1212 cuprates.
Size-Dependent Colors and Luminescences of Organic Microcrystals
Authors: Kasai Hitoshi , Kamatani Hirokazu , Okada Shuji , Oikawa Hidetoshi , Matsuda Hiro , Hachiro Nakanishi Hachiro Nakanishi
Published: October 2002

Perylene microcrystals with different sizes from about 50 nm to about 200 nm were prepared using the reprecipitation method. Their excitonic absorption peaks were found to shift to the high energy side with decreasing crystal size, that is to say, the shifts from that of the bulk crystal were about 500 cm-1 and 1420 cm-1 for 200 nm and 50 nm microcrystals, respectively. Moreover, strong fluorescence from the free-exciton energy level in the microcrystals was observed even at room temperature, which is not usually observed in bulk crystals.
Thermally Stimulated Depolarization Current Study on the Glass Transition of a Liquid Crystalline Copolyester
Authors: Hiroshi Shimizu Hiroshi Shimizu , Takeshi Kitano Takeshi Kitano , Kazuo Nakayama Kazuo Nakayama
Published: October 2002

The glass transition of a thermotropic liquid crystalline copolyester of p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA) was studied by the thermally stimulated depolarization current (TSDC) technique. The poling temperature (T
p) dependence of TSDC spectra revealed the existence of another peak in the vicinity of the glass transition. This TSDC peak was considered to be the sub-T
g relaxation, distinct from the α, β and γ relaxations. It was found that the presence of the sub-T
g relaxation contributed to the apparent broadening of the glass transition of this copolyester.
Patterning of Epitaxial Organic Films by Selective Epitaxial Growth
Authors: Akira Suzuki Akira Suzuki , Toshihiro Shimada Toshihiro Shimada , Atsushi Koma Atsushi Koma
Published: October 2002

A new method of patterning crystalline organic molecular films is proposed and demonstrated. It utilizes a selective growth, or the difference in the sticking coefficient of an organic material on various inorganic substrates in a certain temperature range. The object structure is first patterned on a single-crystalline substrate with an epitaxial film of a different material grown by molecular beam epitaxy (MBE) through a mask, and then a beam of the organic molecule is irradiated uniformly after removing the mask.
Temperature Dependence of the Photoluminescence of Porous Silicon
Authors: Shimizu Azuma , Yamada Yutaka , Izutsu Gouichi , Kouji Yano Kouji Yano , Masanobu Kasuga Masanobu Kasuga
Published: October 2002

Porous silicon layers with red, orange and yellow luminescence were prepared by anodizing silicon wafers in HF-ethanol solutions with different HF concentrations. Temperature dependence of the photoluminescence was systematically measured. The results show that the red emission of a sample prepared in solution with high HF concentration is explained by a configurational coordinate model, while the orange or yellow emission of a sample prepared in solution with low HF concentration is explained by quantum confinement effects.
Electrical Transport Properties of p-GaN
Authors: Nakayama Hisashi , Hacke Peter , Khan Mohammad Rezaul Huque , Detchprohm Theeradetch , Kazumasa Hiramatsu Kazumasa Hiramatsu , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

Electrical transport properties of Mg-doped p-GaN grown by organometallic vapor phase epitaxy were studied between 100 and 700 K. Calculations using Fermi-Dirac statistigs were carried out, identifying the majority carrier to be holes over the whole temperature range considered. The acceptor level is 0.17 ± 0.01 eV. The hole mobility is 10 cm2/V·s and is almost temperature independent from 160 to 300 K. The detailed analysis employing Fermi-Dirac statistics was then extended to determine the temperature dependence of the Fermi level.
Micro-Photoluminescence Study at Room Temperature of Sidewall Quantum Wires Formed on Patterned GaAs (311)A Substrates by Molecular Beam Epitaxy
Authors: Nötzel Richard , Ramsteiner Manfred , Menniger Johann , Trampert Achim , Schönherr Hans-Peter , Lutz Däweritz Lutz Däweritz , Klaus H. Ploog Klaus H. Ploog
Published: October 2002

Lateral quantum wires are grown by molecular beam epitaxy of GaAs/(AlGa)As multilayer structures on patterned GaAs (311)A substrates along the sidewall of 15–20 nm heigh mesa stripes oriented along [01–1]. The wire formation relies on the preferential migration of Ga atoms from the mesa top and bottom toward the sidewall. The quantum wires having a lateral width of ∼50 nm are characterized by micro-photoluminescence spectroscopy between 8 K and room temperature. In the whole temperature regime the quantum wire exhibits a clear luminescence peak, well separated from the quantum well peak at the mesa top and bottom forming the lateral barriers. Micro-photoluminescence linescans reveal the strong spatial confinement of the photogenerated carriers even at room temperature.
Temperature Dependent Breakdown Characteristics in InP/InGaAs Avalanche Photodiodes
Authors: Hyun Kyung Sook , Chan Yong Park Chan Yong Park , Hong Man Kim Hong Man Kim
Published: October 2002

The temperature dependence on the breakdown voltages of InP/InGaAs avalanche photodiode was investigated in the range between -20°C and 100°C. It was found that the normalized first derivative of the breakdown voltage with respect to temperature decreased linearly as the breakdown voltage increased. Furthermore, the extrapolations of all the tested samples converge at the temperature independent limiting value of breakdown voltage. According to our analysis on these phenomena, we propose an empirical formula of temperature dependent breakdown voltages.
Measurements of Temperature Distribution in Polycrystalline Thin Film Transistors Caused by Self-Heating
Authors: Sameshima Toshiyuki , Kohno Yuji Sunaga
Published: October 2002

Transient thermometry was applied to measure temperature distribution caused by self-heating in n-channel poly-Si TFTs on glass. Pt wires 30 nm thick were formed above the Al gate electrode via an intermediate SiO2 layer with positions above the drain edge, middle and the source as temperature sensors. Temperature above the drain edge increased 9 K from room temperature at a power consumption of 20 µW/µm per unit gate width, while it increased only 6 K above the source edge when the TFT was operated in a saturation mode. This results from heat generation being localized near the drain edge. The temperature change with time is also discussed.
Novel Microcantilever for Scanning Thermal Imaging Microscopy
Authors: Yoshihiko Suzuki Yoshihiko Suzuki
Published: October 2002

A novel microcantilever structure for the probe of a scanning thermal imager (STI-probe) which has an integrated pyramidal thin-film microthermocouple is proposed. Using a micromachining process, free-standing microcantilevers having length from 180 µm to 880 µm are fabricated. The STI-probe has an output voltage of 8.43 µV for a unit temperature and a linear thermoelectromotive force for increasing temperature. This probe will be very useful for precise scanning thermal imaging technology.