bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vertical Si-Metal-Oxide-Semiconductor Field Effect Transistors with Channel Lengths of 50 nm by Molecular Beam Epitaxy
Authors: Harald Gossner Harald Gossner , Ignaz Eisele Ignaz Eisele , Lothar Risch Lothar Risch 
Published: October 2002

The growth conditions in molecular beam epitaxy (MBE) were studied for the fabrication of vertical Si-metal-oxide-semiconductor field effect transistors (MOSFET) with channel lengths down to 50 nm. The short channel length imposes severe constraints on the doping profile. MBE growth provided a steepness of 10 nm/dec for boron and 2 nm/dec for antimony. The sharpness of the doping profile was sustained throughout the process by keeping all process temperatures below 700° C. The high crystal quality and the well-defined doping profile was verified by the good performance of a triangular barrier diode. A vertical n-MOSFET with an estimated channel length of 50 nm was grown. The drain and gate characteristics were discussed for a source drain voltage regime from U
sd=0 V to 1 V.
GaAs/AlGaAs Quantum Well Infrared Detectors with an Integral Silicon Grating
Authors: Gou-Chung Chi Gou-Chung Chi , Cheng Juang Cheng Juang 
Published: October 2002

Single quantum well GaAs/AlGaAs infrared photodetectors (QWIPs) with an integral silicon grating have been fabricated. An enhancement of radiation coupling efficiency over a 45° bevel device is observed at 77 K. In addition, this technology enables the device to detect normally incident infrared radiation from the substrate side and makes possible the practical packaging of detector arrays.
A Very Low Level DC Current Amplifier Using Photocoupler Negative Feedback Circuit
Authors: Ikuo Nakamura Ikuo Nakamura , Hiroki Higa Hiroki Higa 
Published: October 2002

In order to improve the response speed of a very low level dc current amplifier, we propose a novel method in which a photocoupler, instead of a high resistor (1010 Ω), is employed for the negative feedback circuit. In this paper, it is shown experimentally that with the proper use of positive feedback, the rise time t
r of 10 µs is obtained for this circuit at the current sensitivity of 10 pA. In comparison, the t
r with the use of the high resistor with the shielding plate is 120 µs. (Here, the current sensitivity is the minimum measurable input signal current that produces an output signal voltage of a very low level dc current amplifier equal to its output noise voltage, or that leads to a signal-to-noise ratio of unity.)
Nanometer Electrode Fabrication Technology Using Anodic Oxidation Resist and Application to Unidirectional Surface Acoustic Wave Transducers
Authors: Kazuhiko Yamanouchi Kazuhiko Yamanouchi , Toshiyasu Meguro Toshiyasu Meguro , Yasuo Wagatsuma Yasuo Wagatsuma , Hiroyuki Odagawa Hiroyuki Odagawa , Keiichi Yamamoto Keiichi Yamamoto 
Published: October 2002

Nanometer lithography technology is very important for high density integrated circuits and higher-frequency-range surface acoustic wave (SAW) devices. The frequency ranges of SAW devices extend to around 10 GHz; therefore a sub-micron technology below 0.1 µm is required. In this paper, we propose new lithography techniques for nanometer fabrication using very thin anodic oxidation films. Since very thin resists (less than 50 nm) can be used in this process, a narrow resist pattern and electrodes can be obtained. The results show the 75 nm width of an interdigital transducer (IDT) made of aluminum with thickness of 30 nm on 128° Y-X LiNbO3. SAW experimental results show the 17 GHz-range characteristics. Also, new lithography technologies are applied to 2 GHz low-loss filters using a unidirectional transducer.
Ge Epitaxial Overlayers on Si(001) Studied by Surface-Sensitive X-Ray Absorption Fine Structure: Evidence for Strain-Induced Surface Rearrangement
Authors: Oyanagi Hiroyuki , Sakamoto Kunihiro , Ryu Shioda Ryu Shioda , Tsunenori Sakamoto Tsunenori Sakamoto 
Published: October 2002

The structure of Ge epitaxial overlayers on well-oriented Si(001) ( Ge

n

/Si(001), n<7) has been studied by the surface-sensitive X-ray absorption fine structure (XAFS) technique in situ after layer-by-layer growth by molecular beam epitaxy (MBE). It is found that surface rearrangements unique to the number of Ge layers take place. For 1 monolayer (ML) Ge on Si(001), elongated Ge dimers with a local structure characteristic of s
2
p
3 configuration are observed, suggesting that surface strain induces a substrate-to-adatom charge transfer. For 2 ML Ge, ∼1/2 of Ge atoms in the second layer are replaced with Si atoms in the third layer, relieving elastic strain in the second layer caused by a large atomic size mismatch ( ∼10%) between the adatom and substrate atom. A possible model structure with the Ge0.5Si0.5 double layer interface is proposed. The results suggest that surface strain induces a site-specific atomic migration channel between the adjacent layers, serving as a driving force of interface mixing associated with the growth of Ge on Si or Si on Ge.
AFM Observation of Self-Assembled Monolayer Films on GaAs (110)
Authors: Hirotaka Ohno Hirotaka Ohno , Makoto Motomatsu Makoto Motomatsu , Wataru Mizutani Wataru Mizutani , Hiroshi Tokumoto Hiroshi Tokumoto 
Published: October 2002

We have confirmed that a self-assembled monolayer (SAM) film of octadecanethiol (ODT), CH3(CH2)17SH, can be formed on a cleaved GaAs (110) surface, by using an atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Circular depressions were observed on the surface after film formation. The area of the circular depressions increased with immersion time, indicating that the solution oxidized the interface between ODT molecules and the GaAs surface, resulting in removal of ODT molecules. The oxidation was considerably faster in pure ethanol solution than that in ODT solution, demonstrating that the SAM film protects the GaAs surface from oxidation. High-resolution lateral force microscope (LFM) images revealed a periodic structure that had two types of lines: periodic lines 0.57 nm apart and lines rotated 55° with respect to them. A structural model of the SAM successfully explained both the features in high-resolution LFM images and the depression depth observed in AFM images.
Linear Arrangement of Motor Protein on a Mechanically Deposited Fluoropolymer Thin Film
Authors: Hitoshi Suzuki Hitoshi Suzuki , Kazuhiro Oiwa Kazuhiro Oiwa , Akira Yamada Akira Yamada , Hitoshi Sakakibara Hitoshi Sakakibara , Haruto Nakayama Haruto Nakayama , Shinro Mashiko Shinro Mashiko 
Published: October 2002

Motor protein molecules such as heavy meromyosin (HMM), one of the major components of skeletal muscle, were arranged linearly on a mechanically deposited fluoropolymer thin film substrate in order to regulate the direction of movement generated by the motor protein. The fluoropolymer film consisted of many linear parallel ridges whose heights and widths were 10 to 20 nm and 10 to 100 nm, respectively. The fluoropolymer ridges adsorbed HMM molecules that were applied onto the film. Actin filaments labeled with rhodamine-phalloidin were observed under a fluorescence microscope moving linearly on the HMM-coated ridges. The observation indicates that HMM molecules were aligned on the fluoropolymer ridges while retaining their function. The velocity of actin movement was measured in this system.
Lateral-Size Control of Trench-Buried Quantum Wires Using GaAs/AlAs Superlattice Layers
Authors: Tetsuomi Sogawa Tetsuomi Sogawa , Seigo Ando Seigo Ando , Hiroshi Kanbe Hiroshi Kanbe 
Published: October 2002

We demonstrated the lateral-size control of GaAs/AlAs trench-buried quantum wires (QWRs) in the region below 20 nm by using GaAs/AlAs superlattice layers (SLs). Scanning electron microscopy images and photoluminescence properties of the trench-buried QWRs revealed that the trench width can be controlled by varying the number of SLs and reduced to about 13 nm by growing 7 pairs of SLs. The GaAs wires in the trenches have a tendency to grow so as to maintain a constant cross-sectional area, which leads to reduction of the energetic broadening of the quantum sub-levels caused by pattern size fluctuation.
GaAs Metalorganic Vapour Phase Epitaxial Overgrowth over nm-Sized Tungsten Wires
Authors: Lars-Erik Wernersson Lars-Erik Wernersson , Kristina Georgsson Kristina Georgsson , Andrej Litwin Andrej Litwin , Lars Samuelson Lars Samuelson , Werner Seifert Werner Seifert 
Published: October 2002

Epitaxial overgrowth of GaAs over nanometer-sized tungsten patterns is studied experimentally. The relationships between the quality of the overgrowth and geometrical parameters, such as crystallographic orientation, metal width, metal thickness, and grating period, are investigated. The overgrown structures are characterized using a scanning electron microscope at top surfaces and at cleaved edges, and by I-V measurements of Schottky diodes formed between the metal grid and the overgrown GaAs. It is established that it is possible to obtain a high-quality overgrowth layer with a completely planarized growth front within 200 nm of growth.
Mesoscopic Phenomena in Microstructures of IV–VI Epilayers
Authors: Grzegorz Grabecki Grzegorz Grabecki , Shojiro Takeyama Shojiro Takeyama , Satoru Adachi Satoru Adachi , Yoshihiro Takagi Yoshihiro Takagi , Tomasz Dietl Tomasz Dietl , Eliana Kamiń Eliana Kamiń , Anna Piotrowska Anna Piotrowska , Ewa Papis Ewa Papis , Norbert Frank Norbert Frank , Günther Bauer Günther Bauer 
Published: October 2002

Precise magnetoresistance measurements on microstructures of photolithographically patterned PbSe epilayers have been performed in the magnetic field range up to 17 T. Unusual, reproducible magnetoconductance fluctuations have been observed. The fluctuation amplitude is about one order of magnitude greater than that predicted for universal conductance fluctuations. Moreover, the fluctuation frequency spectra correspond to the Aharonov-Bohm effect on electron trajectories up to 50 times smaller than the electron mean free path. This strongly points to the ballistic, not diffusive, origin of the observed phenomenon.
Transport through Discrete Energy Levels in Quantum Dots
Authors: Yoshimasa Isawa Yoshimasa Isawa , Futoshi Suwa Futoshi Suwa 
Published: October 2002

The effect of potential fluctuations on a semiconductor quantum dot is exhibited. The height of a series of single peaks in the Coulomb oscillation (CLO) becomes irregular in the presence of potential fluctuations. As the source-drain voltage becomes larger than the quantized level spacing, a single peak broadens and turns into a multiple peak. The asymmetry of the barrier heights and the potential fluctuations in the dot are crucial in this regime. The influence of potential fluctuations on wave functions plays an important role in the transport phenomena in submicrometer devices near pinch-off.
Effects of Lead Particles on the Magnetoresistance of a Two-Dimensional and Quasi-One-Dimensional Electron Gas
Authors: P. Omling P. Omling , H. Linke H. Linke , K. Deppert K. Deppert , L. Samuelson L. Samuelson , L. Theil Hansen L. Theil Hansen , P. E. Lindelof P. E. Lindelof 
Published: October 2002

Very small lead particles have been deposited with random distribution on top of high mobility GaAs/AlGaAs two-dimensional electron gas (2DEG) samples, and the effects on the transport properties of the 2DEG have been studied. Particles more than 5 µm in diameter cause magnetic disorder in the 2DEG in their superconducting state, giving rise to prominent structures in the magnetoresistance. In contrast, spherical particles of 80 to 300 nm diameter do not cause magnetic effects. Electrostatic effects of the nm-sized particles on the transport properties of wide 2DEG structures are very weak, whereas the magnetoresistance properties of a narrow channel were altered significantly in the presence of only a few lead particles smaller than 300 nm. The influence of particles of diameter <300 nm on wide 2DEG samples could be strongly enhanced by melting the particles on the surface.
Thermoelectric Power Studies on 1% Excess Te Doped Pb0.8Sn0.2Te Thin Films
Authors: V. Damodara Das V. Damodara Das , C. Bahulayan C. Bahulayan 
Published: October 2002

Thin films of Pb0.8Sn0.2Te of thicknesses varying between 360 Å and 3400 Å have been prepared by flash evaporation on cleaned glass substrates held at room temperature. Thermoelectric power (TEP) of these films has been evaluated by measuring the thermal emf developed by the integral method in the temperature range 300 K to 500 K. It has been found that TEP of all the films is positive and increases with temperature in the low temperature region and tends to saturate at high temperatures, beyond 400 K. This has been attributed to the pinning of the Fermi level at high temperatures. It was also found that these films did not show the expected linear dependence of TEP on the inverse film thickness.
System for Time-Resolved Observation of Impulsive Soft X-Ray Sources and Its Application to Plasma Focus Experiment
Authors: Takeshi Yanagidaira Takeshi Yanagidaira , Hiroshi Kurita Hiroshi Kurita , Katsumi Hirano Katsumi Hirano 
Published: October 2002

A soft X-ray pinhole camera system for time-resolved, one-dimensional (1D) measurement of an impulsive source whose energy is in the range from 1 keV to 20 keV is developed. The system is based on the filtered pinhole camera. The pinhole image is divided into six channels in the direction of the electrode axis through slits and bundled fiber optics. Each channel is detected with a scintillator-photomultiplier combination. The temporal resolution of this system is 5.2 ns. The absolute sensitivity of the channel is ∼4.2×10-20 A/[photons/(mrad2·s)]. This system was successfully used to observe the time evolution of the soft X-ray source generated with a plasma focus device with a gas-puffed target.
Hierarchy Optimization: A Means to Enhance Efficiency in E-Beam and Optical Lithography
Authors: K. Kalus Anja Rosenbusch , Hiroyuki Endo Hiroyuki Endo , Yasuki Kimura Yasuki Kimura , Akihiro Endo Akihiro Endo 
Published: October 2002

In the e-beam lithography arena the proximity effect correction (PEC) of large la youts is still regarded as an insurmountable hurdle. The central processing unit (CPU) time for today's memory layouts (64 Mb) extends into weeks and file sizes into Gigabytes. In this paper a new concept for hierarchical data handling is introduced, the hierarchy reorganization. It paves the way for practical applications of very large layouts. The initial layout is reorganized according to correction-dependent criteria. The term hierarchy factor, which is a measure of the compaction of the given hierarchy tree, is introduced. This paper presents and explains the theoretical rules of the hierarchy optimization. The problems of hierarchical processing are demonstrated and solutions given. The solutions fall into two categories: the first one is common to all hierarchical processing, whereas the second one is application-specific. As an example, the hierarchical processing is applied to the proximity effect correction. Scanning electron microscope (SEM) images of memory chips are shown by comparing corrected with uncorrected wafers. Files sizes and processing times of all relevant processing steps in comparison with flat operation (not exploiting the hierarchy) are given.
The Characteristics of Nitrogen Implanted Tungsten Film as a New Diffusion Barrier for Metal Organic Chemical Vapor Deposited Cu Metallization
Authors: Kwon Chul Soon , Kim Yong Tae , Choi Suk-Ki Min 
Published: October 2002

Nitrogen-implanted W thin film (W-N+) has been proposed as a new diffusion barrier for Cu metallization. The crystalline phase of W-N+ thin film is transformed from polycrystalline to amorphous by the implantation of 1–3 ×1017 N+/cm2. However, if the dosage of N+ is less than 6 ×1016 N+/cm2 it is difficult to form the amorphous phase in the W film. The comparison of this amorphized W-N+ diffusion barrier with the conventional W film shows that the amorphized W-N+ diffusion barrier is very effective for preventing the Cu diffusion even at the annealing temperature of 800°C for 30 min, whereas the conventional W film cannot withstand annealing at 600°C for 30 min. Our result at 800°C for 30 min is a new and excellent record for preventing Cu diffusion.
Transport Characterization of Schottky In-Plane Gate Al 0.3Ga 0.7As/GaAs Quantum Wire Transistors Realized by \twltibIn-Situ Electrochemical Process
Authors: Hiroshi Okada Hiroshi Okada , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa 
Published: October 2002

The low-temperature transport properties of the novel Al0.3Ga0.7As/GaAs Schottky in-plane gate (IPG) quantum wire transistor realized by the in-situ electrochemical process were studied. The device showed good field-effect transistor (FET) characteristics with excellent gate control and complete pinch-off. Quantized conductance in the units of 2e
2/h was clearly seen at 4 K. The first plateau persisted up to 40 K. Shubnikov-de Haas oscillation measurements showed an extremely weak dependence of the carrier density on the gate bias, indicating that the Schottky IPG controls the wire width without changing the sheet carrier density. Application of a magnetic field widened the conductance plateaus. Under harmonic approximation for the electrostatic confinement potentials, a subband spacing of \hbarω0=4–5 meV was obtained.
Comparison of Propagation Losses of Single-Mode GaAs/AlGaAs Waveguides in a Three- and a Five-Layer Structure
Authors: Young Tae Byun Young Tae Byun , Kyung Hyun Park Kyung Hyun Park , Sun Ho Kim Sun Ho Kim , Sang Sam Choi Sang Sam Choi , Tong Kun Lim Tong Kun Lim 
Published: October 2002

Single-mode GaAs/AlGaAs ridge waveguides with a three- and a five-layer heterostructure have been designed using an effective index method and fabricated using a metalorganic chemical vapor deposition (MOCVD) technique and the chemical wet etching method. The propagation loss was measured by the Fabry-Perot resonance method and sequential cleaving experiment at 1.31 µm wavelength. The propagation loss is as low as 0.62 dB/cm for waveguides with a double heterostructure. For five-layer waveguides with a W-shaped index profile, it is 0.23 dB/cm, comparable to the lowest loss value of semiconductor waveguides yet reported. Therefore the W-type waveguides provide a useful basis for low-loss guided-wave devices for integrated optoelectronics.
Magnetically Excited Plasma Oxidation of Si
Authors: Hideaki Nagasawa Hideaki Nagasawa , Hiroyasu Kitajima Hiroyasu Kitajima , Daisuke Kitayama Daisuke Kitayama , Yoshinaga Okamoto Yoshinaga Okamoto , Hideaki Ikoma Hideaki Ikoma 
Published: October 2002

High-quality Si dioxide was successfully grown at room temperature using a magnetically excited plasma oxidation technique. Helicon waves were probably excited under the growth conditions used. Excellent capacitance-voltage characteristics were obtained after annealing of these oxide films in oxygen ambient for 15 min at 300°–500°C. The growth rate was somewhat low. However, the film thickness increased substantially with annealing. X-ray photoelectron spectroscopic studies indicated that high-quality Si oxides without suboxides were grown even at room temperature.
Electronic NO 2 Sensor Using Merocyanine-Doped Langmuir Blodgett Films
Authors: Masayuki Morisawa Masayuki Morisawa , Shunya Morita Shunya Morita , Shinya Sakamoto Shinya Sakamoto , Shinzo Muto Shinzo Muto , Hiroshi Ito Hiroshi Ito 
Published: October 2002

The NO2 sensor using merocyanine-doped Langmuir-Blodgett (LB) films, the mechanism of which is based on a change in surface conductivity due to the attachment of electrophilic gas molecules, was investigated. Its sensitivity depended on the number of LB layers. The sensor with 5 layers was most sensitive and had a very fast response time of less than 5 s, good reproducibility and maximum sensitivity in the low NO2 concentration range of 0 to 10 ppm.
Effect of Electron Beam Irradiation on Si Surface Cleaning in Ultrahigh-Vacuum System
Authors: Hiroshi Miura Hiroshi Miura , Kouichi Ohtaka Kouichi Ohtaka , Daisuke Shindo Daisuke Shindo 
Published: October 2002

Effect of electron beam irradiation (15 kV) on Si surface cleaning prior to epitaxial growth in an ultrahigh-vacuum system was investigated. A CaF2 film was epitaxially grown on the Si surface, and the interface was observed by high-voltage electron microscopy. Amorphous layers, which were observed in the interface prepared with conventional thermal treatment at 750°C, became much smaller with electron beam irradiation after the thermal treatment. Based on the electron microscope observation, the effect of electron beam irradiation on Si surface cleaning was briefly discussed.
High-Sensitivity SOI MOS Photodetector with Self-Amplification
Authors: Hideaki Yamamoto Hideaki Yamamoto , Kenji Taniguchi Kenji Taniguchi , Chihiro Hamaguchi Chihiro Hamaguchi 
Published: October 2002

A high-sensitivity silicon-on-insulator (SOI) metal-oxide-silicon (MOS) photodetector compatible with conventional silicon technology is proposed. Its operation principle is based on that of a lateral bipolar transistor in spite of an SOI MOS device structure. Photodetectors with narrow base width or short channel length have high current gain which is attributed to a self-biased effect under illumination. Current gain as high as 100 has been achieved for the device with a channel length of 1.0 µm. Measured intrinsic response time for optical pulses is 19 µs for the photodetector with a channel length of 0.7 µm.
A Novel Short-Cavity Laser with Deep-Grating Distributed Bragg Reflectors
Authors: Akihiro Matsutani Toshihiko Baba , Toshikazu Mukaihara Toshikazu Mukaihara , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga 
Published: October 2002

We have proposed a novel short-cavity laser with deep-grating distributed Bragg reflectors (DBRs). We monolithically fabricated a 0.98 µm InGaAs/AlGaAs device and 1.55 µm GaInAsP/InP device using electron beam lithography and a reactive ion beam etching technique. The lasing operation of both devices was achieved at room temperature. From a comparison of the threshold current from the experimental result with that from the theoretical result, the reflectivity of formed DBRs was estimated to be less than 30%. The theory also predicts that the ideal DBR exhibits a high reflectivity over 97% even with 3 periods of grating. It achieves lasing operation with a threshold current less than 100 µA using a cavity shorter than 10 µm. This high performance is realized by reducing the surface roughness and damage to etched sidewalls and improving the reflectivity of the DBR.
Characterization of Charged Traps near Si–SiO2 Interface in Photo-Induced Chemical Vapor Deposited SiO2 Film
Authors: Hideaki Yamamoto Hideaki Yamamoto , Shinya Iwasaki Shinya Iwasaki , Katsuhide Okumura Katsuhide Okumura , Takeshi Kanashima Takeshi Kanashima , Masanori Okuyama Masanori Okuyama , Yoshihiro Hamakawa Yoshihiro Hamakawa 
Published: October 2002

Charged traps near the Si–SiO2 interface in a SiO2 film deposited by photo-induced chemical vapor deposition (photo-CVD) have been analyzed by the photo I–V method. In the as-deposited film, positively charged traps distribute in the region between 2 nm and 10 nm from the Si–SiO2 interface, and their density decreases monotonically with increasing depth. The density of traps in the region between 2 nm and 4 nm is decreased by annealing in N2 or O2, and that of traps in the region between 4 nm and 10 nm is decreased only by annealing in O2. Furthermore, the results of electron spin resonance (ESR) analysis suggest the possibility that the positively charged traps in the 2–4 nm region are related to the defects observed in ESR.