bluuebunny/crossref_metadata_2025 huggingface dataset:
Negative Ions in 13.56 MHz Discharge of SF6Gas in a Planar Diode
Authors: Nagaseki Kazuya , Ishikawa Itsuo , Nishimura Eiichi , Saito Yukinori , Shinji Suganomata Shinji Suganomata
Published: October 2002

Mass spectra of negative ions were measuredin situby direct sampling from SF6discharges at 13.56 MHz separately in the two cases of the grounded electrode attached with and without Si wafer. In both cases, F-is observed dominantly, with smaller amounts of SF-5and SF-6. In the case with Si wafer, however, all these intensities decrease overall. Positive ions SF+2and SF+3are predominant in the cases with and without Si wafer, respectively. Negative ions SF-2and SF-3, however, are hardly observed regardless of whether Si wafer is present or not.
A Way of Distinguishing Chaos from Random Fractal Sequences Based on the Difference in Time Reversal Symmetry
Authors: Naoki Tanaka Naoki Tanaka , Hiroshi Okamoto Hiroshi Okamoto , Masayoshi Naito Masayoshi Naito
Published: October 2002

We propose a method of distinguishing chaos from random fractal sequences which have been difficult to discriminate from chaos. In the proposed method, time series is predicted both toward the future and toward the past, and the accuracy of the two types of predictions is compared. We show, considering the time reversal symmetry of time series, that if the time series is chaotic and originates from a dissipative dynamical system, the accuracy is better for the future prediction than for the past prediction, whereas the accuracy is the same if the time series is a random fractal sequence. The method is also applicable to distinguishing between chaos and stationary noise.
Grazing Incidence X-Ray Diffraction Study on Effect of Implanted BF+
2 and Linewidth on Titanium Silicidation
Authors: Tomita Hirofumi , Komiya Satoshi , Horii Yoshimasa , Tomoji Nakamura Tomoji Nakamura
Published: October 2002

The C49 and C54 fractions in TiSi2 are examined quantitatively by the grazing incidence X-ray diffraction method in order to study the effect of BF+
2 implanted in Si substrates and linewidth on TiSi2 silicidation and the phase transition from C49 to C54. B
F
+
2 implantation suppresses both silicidation and the phase transition, and the phase transition is also markedly suppressed on narrow lines. As a result, all the C49 TiSi2 remains for 0.5 µ m lines with B
F
+
2 dose of 2×1015 cm-2 after the 2nd rapid thermal annealing (800° C, 30 s). Furthermore, we have found that the grains of C49 TiSi2 are preferentially oriented to highly implanted substrates. This indicates that the phase of these grains is stable thermally and difficult to transform to C54 phase.
Giant Magnetoresistance of (110)-Oriented NiFe/Cu Multilayer Grown on MgO(110)
Authors: Takebayashi Shigeto , Toshio Mukai Toshio Mukai
Published: October 2002

A multilayer consisting of 40 periods of NiFe (Ni81, Fe19 in wt%) and Cu, the thicknesses of which are 1 nm each, was deposited on an underlayer of 20 nm NiFe grown on a MgO(110) single-crystal substrate. A strongly anisotropic behavior in its magnetoresistive property is evident when the magnetic field is applied along the [11̄0] and [001] directions. Its crystallographic relationship with the substrate is assigned as NiFe/Cu(110)||
MgO(110) perpendicular to the plane of the film, and NiFe/Cu[1\bar10]∥MgO[1\bar10], NiFe/Cu[001]||
MgO[001] in the plane of the film.
InGaAs-GaAs-InGaP Distributed Bragg Reflector Buried Heterostructure Strained Quantum Well Lasers
Authors: Sin Y. K. , Horikawa H.
Published: October 2002

We report on the first demonstration of InGaAs-GaAs-InGaP distributed Bragg reflector (DBR) buried heterostructure strained quantum well lasers. The devices, entirely grown by three step MOVPE process, show a CW threshold current of 7.2 mA measured at RT and this is, to the best of our knowledge, the lowest CW threshold current ever obtained from GaAs based DBR lasers. The monomode oscillation is obtained with the sidemode suppression ratio of 25 dB, the Bragg wavelength at 0.96 µ m, and the temperature sensitivity of DBR modes being 0.53 Å/° C between 20 and 35° C.
Photoluminescence Spectrum Study of the GaAs/Si Epilayer Grown by using a Thin Amorphous Si Film as Buffer Layer
Authors: Hao Mao-Shen , Liang Jun-Wu , Zheng Lian-Xi , Deng Li-Seng , Xiao Zhibo , Hu Xiong-Wei
Published: October 2002

Recently, we reported successful growth of high-quality GaAs/Si epilayers by using a very thin amorphous Si film as buffer layer. In this paper, the impurity properties of this kind of GaAs/Si epilayers have been studied by using PL spectrum, SIMS and Hall measurement. Compared to a typical PL spectrum of the GaAs/Si epilayers grown by conventional two-step method, a new peak was observed in our PL spectrum at the energy of 1.462 eV, which is assigned to the band-to-silicon acceptor recombination. The SIMS analysis indicates that the silicon concentration in this kind of GaAs/Si epilayers is about 1018 cm-3. But its carrier concentration (about 4×1017 cm-3) is lower than the silicon concentration. The lower carrier concentration in this kind of GaAs/Si epilayer can be interpreted both as the result of higher compensation and as the result of the formation of the donor-defect complex. We also found that the high-quality and low-Si-concentration GaAs/Si epilayers can be regrown by using this kind of GaAs/Si epilayer as substrate. The FWHM of the X-ray (004) rocking curve from this regrowth GaAs epilayer is 118′′, it is much less than that of the first growth GaAs epilayer (160′′) and other reports for the GaAs/Si epilayer grown by using conventional two-step method (∼200′′).
Dissociative Photoionization of Bis(dimethyl-µ-isopropylamido-aluminum) and Bis(dimethyl-µ-t-butylamido-aluminum) in the Region h ν=65-133 eV by Mass Spectrometry
Authors: Park Seung Min , Boo Bong Hyun , Kim Yoonsoo , Park Joon T. , Koyano Inosuke
Published: October 2002

The dissociative photoionization studies of bis(dimethyl-µ-isopropylamido-aluminum) and bis(dimethyl-µ-t-butylamido-aluminum) in the photon energy range of 67-133 eV have been performed as preliminary studies of synchrotron radiation single-precursor chemical vapor deposition. Photoelectron-photoion coincidence and photoion-photoion coincidence mass spectra are analyzed to understand the effects of Al:2 p and Al:2 s core excitation on the branching ratios of photofragments produced by absorption of synchrotron radiation.
High-Quality, High-Rate SiO2 and SiN Films Formed by 400 kHz Bias Electron Cyclotron Resonance-Chemical Vapor Deposition
Authors: Fukuda Takuya , Saito Katsuaki , Ohue Michio , Shima Kenzou , Momma Naohiro
Published: October 2002

A new electron cyclotron resonance (ECR) plasma CVD system is proposed to form high-quality SiO2 and SiN films at high rates. The system applies 400 kHz voltages which ions can follow to the substrate. The system efficiently produces, without heating: 1) SiO2 films in which density and Si-O bond strength are equivalent to those of a thermally oxidized (about 1000° C) film for which deposition rate is higher than 1.2 µ m/min and 2) Si-H bond-free SiN films in which density and resistivity are higher than those of films formed by conventional plasma CVD systems and for which deposition rate is higher than 0.8 µ m/min.
Amorphous Avalanche Photodiode with Large Conduction Band Edge Discontinuity
Authors: Sugawa Shigetoshi , Kozuka Hiraku , Atoji Tadashi , Tokunaga Hiroyuki , Hisae Shimizu Hisae Shimizu , Kazuaki Ohmi Kazuaki Ohmi
Published: October 2002

An amorphous avalanche photodiode (APD) with a heterojunction of hydrogenated amorphous silicon carbide (a-SiC:H) and hydrogenated amorphous silicon germanium (a-SiGe:H) was formed. The band gaps of a-SiC:H and a-SiGe:H are 3.5 eV and 1.55 eV, respectively. The discontinuity of conduction bands at the heterojunction is larger than the band gap of a-SiGe:H. In this amorphous APD, photocurrent multiplication is observed under low electric field. The quantum efficiency starts to exceed unity when the conduction band discontinuity becomes larger than the band gap of a lower-gap material, and it is likely to saturate at 2. The slope of photoelectric conversion characteristics is 1.00. The multiplication is explained by the impact ionization process at the band edge discontinuity region.
Anomalously Enhanced Boron Diffusion in the Base of SiGe HBTs Induced by Phosphorus Implants into Polysilicon Emitters
Authors: Shuji Ito Shuji Ito , Satoshi Nishikawa Satoshi Nishikawa
Published: October 2002

The impact of phosphorus implants into polysilicon emitters on boron diffusion in the underlying single-crystal base region of SiGe heterojunction bipolar transistors has been investigated. Anomalously enhanced boron diffusion, which is believed to be induced by implant-induced excess interstitials diffusing into the single-crystal region through the polysilicon emitter, is observed after annealing. In situ phosphorus-doped polysilicon is shown to be very effective in suppressing the diffusion enhancement and in realizing a very sharp boron profile.
Surface Observation and Modification of Si Substrate in NH4F and H2SO4 Solutions
Authors: Ando Atsushi , Miki Kazushi , Matsumoto Kazuhiko , Shimizu Tetsuo , Morita Yukinori , Tokumoto Hiroshi
Published: October 2002

Atomic force microscopy (AFM) images of a chemically oxidized p-type Si(111) substrate in a 0.3 M NH4F solution have been investigated to study the topographical change occurring during surface etching. During etching of the oxide layers, elongated structures along the <1*BAR*1*BAR*0> direction were observed. After the oxide layers were completely etched, anisotropic surface etching occurred, as it does in dilute alkaline solutions. We have also demonstrated surface modification of an H-terminated p-type Si(111) substrate on a nanometer scale using electrochemical scanning tunneling microscopy (ESTM) in a 0.2 M H2SO4 solution. A fine line of width as small as 12 nm was obtained. The dependence of the size of modified surface features on the conditions of the modification is studied.
Effects of Dielectrics on the Characteristics of Large-Area Silicon Microstrip Sensors
Authors: Tsay Wen-Chin , Chen Yen-Ann , Laih Li-Hong , Hong Jyh-Wong , Chen Augustine E. , Lin Willis T. , Chang Yuan-Hann , Hou Suen R. , Hsu Shih-Liang , Li Chung-Ren , Ting Hsien-Jen , Chiang Song-Tsang
Published: October 2002

An 8×4 cm2 single-sided silicon microstrip sensor with coupling capacitors and polysilicon bias resistors has been fabricated with planar technology. The oxide-nitride-oxide (ONO) films have been chosen to replace the usual SiO2 layer as the dielectric of the coupling capacitor. In conjunction with a reordering of the process sequence for layer formations, the proposed process could be used to fabricate sensors with self-moisture protection and free from the effect of pinholes. From the measurement results of special p-n junction test structures, we found that their leakage current was dominated by that of the sidewall one. Stress measurement and Sirtl-etch analysis revealed that the sidewall leakage current was increased by the dielectric stress and implantation damage. A boron solid-source predeposition process was employed to reduce this leakage current. From the results of electrical measurement and beam test on sensors, it was shown that the proposed process was able to produce sensors having very good performance.
Direct Observation of Electron Jet from a Point Contact
Authors: Nagamune Yasushi , Noda Takeshi , Watabe Hiroaki , Ohno Yuzo , Hiroyuki Sakaki Hiroyuki Sakaki , Yasuhiko Arakawa Yasuhiko Arakawa
Published: October 2002

We report on the photoluminescence image around a point contact fabricated in an InGaAs/GaAs quantum well using a micro-photoluminescence measurement technique. The photoluminescence image was strongly influenced by majority electron flow from the point contact, where the majority electron flow greately reduced radiative recombination of electron-hole pairs generated by the laser illumination. Using this effect we demonstrated visualization of electron flow from the point contact.
Surface Reconstruction of GaP (001) for Various Surface Stoichiometries
Authors: Yoshikawa Masahiro , Nakamura Atsushi , Takashi Nomura Takashi Nomura , Kenji Ishikawa Kenji Ishikawa
Published: October 2002

The surface stoichiometry and reconstruction of GaP (001) are investigated by means of reflection high-energy electron diffraction and surface photo-absorption. The experiments were carried out using a solid-source molecular beam epitaxy system with a cracker cell as a P source. When the amount of Ga supplied to the surface is over 2 monolayer (ML), the 2×4 reconstruction corresponding to the P-stabilized surface is observed in spite of the existence of excess Ga on the surface. The change of surface reconstruction may be interpreted as follows: the surface is a Ga-terminated structure up to 2 ML of Ga supply, then Ga atoms move to some nonperiodic sites such as Ga droplets.
Vanishing of Negative Differential Resistance Region due to Electric Field Screening in Wannier-Stark Localization Type Self-Electro-Optic Effect Devices
Authors: Makoto Hosoda Makoto Hosoda , Kouji Tominaga Kouji Tominaga , Toshihide Watanabe Toshihide Watanabe , Kenzo Fujiwara Kenzo Fujiwara
Published: October 2002

We report absorption saturation behaviors of the photocurrent versus reverse bias voltage characteristics (i–V characteristics) under high intensity optical pulse excitation in short-period GaAs/AlAs superlattices. While a negative differential resistance (NDR) region in the i–V curve normally appeared due to the Wannier–Stark localization effect under low intensity excitation, vanishing of the NDR was observed under high excitation. Simultaneously, an anomalously stretched photocurrent tail and long-lived photoluminescence were observed. These phenomena are clearly explained by electric field screening caused by remaining photogenerated holes in the superlattice region. Simulation results of carrier transport in thin-barrier superlattices using one-dimensional Green's function for the electric potential explain well the experimental results.
Simulation and Observation of the Step Bunching Process Grown on GaAs (001) Vicinal Surface by Metalorganic Vapor Phase Epitaxy
Authors: Ishizaki Jun-ya , Kazunobu Ohkuri Kazunobu Ohkuri , Takashi Fukui Takashi Fukui
Published: October 2002

The step bunching processes on GaAs (001) vicinal surfaces grown by metalorganic vapor phase epitaxy (MOVPE) are investigated by experiment and the simulation method. In the early stage of the growth, the step bunching height and the terrace widths increase linearly and saturate with increasing layer thickness. The step bunching height and the terrace widths are estimated by the Monte Carlo simulation. From the fitting of the simulated step bunching process to that process of the experiment, the activation energy of the up-side and down-side step sites compared with that of the terrace sites are obtained. Furthermore, the terrace width saturation mechanism is clarified.
Stacked InAs Self-Assembled Quantum Dots on (001) GaAs Grown by Molecular Beam Epitaxy
Authors: Sugiyama Yoshihiro , Nakata Yoshiaki , Imamura Kenichi , Muto Shunichi , Naoki Yokoyama Naoki Yokoyama
Published: October 2002

We report stacked InAs self-assembled quantum dot (QD) structures separated by GaAs interval layers grown by molecular beam epitaxy on a (001) GaAs substrate. The InAs QDs were vertically aligned up to the 9th layer. Strain in the interval layer induced by the lower QD strongly influences the upper QD alignment. A large defect due to lateral In segregation was observed with multiple stacked InAs self-assembled QD structures, which suppresses further vertical alignment of QDs in the upper region and decreases photoluminescence intensity drastically. Optical memory effect of InAs QDs buried in Schottky barrier diode was observed with memory retention time of 0.48 ms for the first time.
Transition from Semi-Classical to Quantum Transport in Quasi-Ballistic Wires
Authors: Yuichi Ochiai Yuichi Ochiai , Kazunuki Yamamoto Kazunuki Yamamoto , Kohji Ishibashi Kohji Ishibashi , Jonathan Paul Bird Jonathan Paul Bird , Yoshinobu Aoyagi Yoshinobu Aoyagi , Takuo Sugano Takuo Sugano , Katsuichi Tankei Katsuichi Tankei , Yosuke Nagaoka Yosuke Nagaoka
Published: October 2002

We have found evidence of a transition from the semi-classical to quantum transport in quasi-ballistic narrow wires constructed in 2DEG system of a GaAs/AlGaAs heterojunction. By increasing the ratio of the mean free path to the wire length while keeping the wire width constant, we find a clear offset between the semi-classical and the quantum behaviors in the two-terminal measurement of the wire resisitance. We can explain such an offset by taking into account the transmission probability of electron waves propagating in the wire.
Low-Threshold-Current and Single-Mode Surface-Emitting Laser Buried in Amorphous GaAs
Authors: Park Hyo-Hoon , Yoo Byueng-Su , Chu Hye Yong , Lee El-Hang , Park Min Soo , Ahn Byung Tae
Published: October 2002

We propose a vertical-cavity surface-emitting laser buried in low-temperature-grown amorphous GaAs (a-GaAs), which was found to be effective for surface passivation of an etched cavity and suppression of high-order transverse modes. The deposition of highly resistive a-GaAs layer on an InGaAs/GaAs active region and AlAs/GaAs mirror layers yielded a significant improvement in threshold current density and differential quantum efficiency. The maximum currents maintaining a stable fundamental transverse mode were also increased by the antiguide effect of a-GaAs with a high refractive index. For a 10-µm-diameter device, we attained a stable single-mode emission with a threshold current of 0.7 mA.
Device Physics and Modeling of Multiple Quantum Well Infrared Photodetectors
Authors: Ershov Maxim , Hamaguchi Chihiro , Victor Ryzhii Victor Ryzhii
Published: October 2002

In this paper we present the physical effects in quantum well infrared photodetectors (QWIPs) utilizing intersubband electron transitions. We show, using numerical modeling, that the operation of QWIP is associated with the nonuniform distribution of the electric field and other physical quantities due to the recharging of the QWs near the emitter contact. The high electric field in the emitter barrier which provides tunneling electron injection is controlled by applied voltage and infrared radiation. The transient photoelectric effects in QWIPs are determined by three time constants–electron capture time to the QWs, transit time through the QWIP structure, and recharging time of the QWs. The transient photocurrent in QWIPs with high photocurrent gain is composed of two components. The fast transient is limited by the carrier transit time, and the slow transient, exhibiting the multiplication of photocurrent, is governed by the QW recharging time. This study shows that contact and distributed effects play an important role in determining both the steady-state and transient QWIP characteristics.
Observation of Oxide-Thickness-Dependent Interface Roughness in Si MOS Structure
Authors: Junji Koga Junji Koga , Shin-ichi Takagi Shin-ichi Takagi , Akira Toriumi Akira Toriumi
Published: October 2002

The relationship between roughness at the Si/SiO2 interface and the oxide thickness was investigated by means of a nondestructive measuring method, using the Si metal-oxide-semiconductor (MOS) structure. It was demonstrated that the Si/SiO2 interface roughness recovers during thermal oxidation. This recovery process was also verified by observation with the transmission electron microscope (TEM). It was found that the recovery effect on the roughness at the Si/SiO2 interface depends on the oxidation process and that it is more significant in wet oxidation than in dry oxidation.
Effect of Nitrogen Profile on Tunnel Oxynitride Degradation with Charge Injection Polarity
Authors: Arakawa Tomiyuki , Matsumoto Ryoichi , Akio Kita Akio Kita
Published: October 2002

The relationship between nitrogen profiles and polarity dependence of wearout and breakdown in oxynitride films was investigated. With positive bias stress, higher concentration of nitrogen atoms near an oxynitride/Si interface (∼2 at.%) and in the oxynitride bulk (∼0.3 at.%) reduce charge trap and interface state generation, and produce greater charge-to-breakdown (Q
bd). In contrast, with negative bias stress, nitrogen atoms near an interface decrease the number of charge traps, but, cannot reduce interface state generation, and thus give smaller Q
bd. Furthermore, nitrogen atoms near an oxynitride surface (over 1.5 at.%) cause undesirable results for both bias stresses. Optimum nitrogen profile in an oxynitride film is discussed the viewpoint of reliability for both bias stresses.
Properties of “Stoichiometric" Silicon Oxynitride Films
Authors: Le-Nian He Le-Nian He , Takao Inokuma Takao Inokuma , Seiichi Hasegawa Seiichi Hasegawa
Published: October 2002

The properties of amorphous SiOxNy films prepared by rf glow discharge of a SiH4–O2–NH3 mixture at 300° C are investigated as functions of the O content, x, and the N content, y. A relationship of 2x + 2.8y = 4 was found between x and y. This result suggests that the densities of homobonds, such as Si–Si, O–O and N–N, and of Si–H and O–H bonds are sufficiently lower than those of Si–O and Si–N bonds. The absence of splitting of stretching absorption bands arising from Si–O and Si–N bonds suggests that the film is a homogeneous alloy. The properties of the dangling bonds and their origins are discussed.
Two-Domain Liquid Crystal Displays Fabricated by Parallel Fringe Field Method
Authors: A. Lien A. Lien , R. A. John R. A. John
Published: October 2002

The parallel fringe field method with a simple pixel structure is proposed to fabricate the two-domain twist nematic (TDTN) liquid crystal display (LCD) to improve the viewing angle behavior of conventional LCDs. The three-dimensional simulation results showed that two pairs of parallel fringe fields drive liquid crystal molecules in two areas of the pixel to tilt in two opposite directions and thus two domains are formed. The experimental results on the test panels confirmed the simulation results. Furthermore, a thin film transistor (TFT) addressed TDTN panel fabricated using this method demonstrated a factor of two improvement in the vertical viewing angle over the conventional single-domain TFT/TN panel.
Time-Dependent Dielectric Breakdown of Interlevel Dielectrics for Copper Metallization
Authors: Miyazaki Hiroshi , Hinode Kenji , Kobayashi Yoshio Homma
Published: October 2002

Bias-temperature stressing of Cu/dielectric/Si capacitors demonstrated that time-dependent dielectric breakdown (TDDB) lifetime strongly depends on dielectric materials. Phosphosilicate glass (PSG) films had much higher immunity from TDDB than thermally grown SiO2. This higher immunity of PSG films is attributed to their greater suppression of Cu diffusion. They provide good protection against Cu contamination of devices. The lifetime (τ) of plasma-enhanced chemical-vapor-deposited TEOS (PECVD–TEOS) films was found to be related to the electric field (E) by using Peek's law (E∝τ-1/4). Using this law, the lifetime becomes rapidly longer than does the previous expectation when the electric field reduces. This suggests PECVD–TEOS films have the potential to be used as interlevel dielectrics for Cu metallization.
Growth Mechanisms of YBa2Cu3O\ssmbix Films Prepared by RF Thermal Plasma Evaporation
Authors: Tsujino Jiro , Hisataka Yakabe Hisataka Yakabe , Yuh Shiohara Yuh Shiohara
Published: October 2002

YBa2Cu3O

x

films prepared by rf thermal plasma evaporation exhibited spiral growth in a wide range of deposition conditions from observations by atomic force microscopy (AFM). However, surface morphology, for example, step width (λ), grain size, and grain shape, varied with deposition conditions. Because surface morphology is affected by growth mechanisms, growth mechanisms can be elucidated by analyzing the change in morphology with deposition conditions. In this study, we investigated the relationship between λ and deposition conditions from a viewpoint of supersaturation. As a result, λ increased with increasing substrate temperature and decreasing raw powder feeding rate, decreasing supersaturation in both cases. In addition, the change in λ and growth rates was explained well by the change in supersaturation using a model based on the BCF theory.
The Unstable Resonator with a Stable Resonator Core
Authors: Nanri Kenzo , Mabuchi Katsuo , Tomoo Fujioka Tomoo Fujioka
Published: October 2002

A new type of the laser resonator, the unstable resonator with a stable resonator core, is proposed. The simple analysis using Kirchhoff diffraction equation revealed that this resonator is suitable for the low gain, large aperture laser medium such as the chemically pumped oxygen-iodine laser.
Optical and Structural Properties of Proton-Exchanged Waveguides in Y-Cut ZnO:LiNbO 3
Authors: Wei Xing Hou Wei Xing Hou , Tow Chong Chong Tow Chong Chong
Published: October 2002

Fabrication and characterisation of proton exchanged planar optical waveguides in Y-cut ZnO:LiNbO3 crystal using adipic acid as proton source are reported in this paper. These waveguides have a linear-step index profile with a surface index increase of 0.138 at the wavelength of 0.633 µ m. The activation energy Q and diffusion constant D
0 for the proton exchange process are characterised optically to be 95.32 KJ/mol and 9.61×109 µ m2/h. A critical thickness of about 2 µ m for proton exchanged y-cut ZnO:LiNbO3 waveguides is optically determined in our experiments. Surface damage is observed for those waveguides with layer thickness larger than this critical value. The strains in y-cut waveguides are measured by using double-crystal X-ray symmetric and asymmetric diffraction method. Based on the measured data, an explanation is given for the surface damage occurred on y-cut samples.
Design and Fabrication of InGaAs/GaAs Quantum Wires for Vertical-Cavity Surface-Emitting Lasers
Authors: Hatori Nobuaki , Mukaihara Toshikazu , Hayashi Yukio , Ohnoki Noriyuki , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: October 2002

A basic design and fabrication of InGaAs/GaAs quantum wires (QWRs) is discussed for the purpose of realizing vertical-cavity surface-emitting lasers (VCSELs). A structure of QWR VCSELs is presented for low-threshold operations and a threshold current density of 100 A/cm2 is obtained. A novel method for fabricating densely packed QWRs on V-grooved substrates is demonstrated by using low-pressure metalorganic chemical vapor deposition. Polarization anisotropy was observed by both photoluminescence and current injection measurements.
Temperature Dependence of Shear Piezoelectric Properties of Poly(vinylidene fluoride) Studied by Piezoelectric Resonance Method
Authors: Kenji Omote Kenji Omote , Hiroji Ohigashi Hiroji Ohigashi
Published: October 2002

Elastic and dielectric anisotropies, and shear piezoelectric properties of uniaxially oriented poly(vinylidene fluoride) (PVDF) were determined in the temperature range from 10 K to 400 K by a piezoelectric resonance method. The shear piezoelectric stress constant e
24 increases above the primary dispersion temperature, while e
15 decreases markedly and tends to zero at 390 K: e
24 and e
15 are, respectively, 28 mC/m2 and 38 mC/m2 at 10 K, and 48 mC/m2 and 15 mC/m2 at 295 K (where the coordinate axes X and Z in the film refer to the stretching axis and poling axis, respectively). The temperature dependences of e
24 and e
15 are analyzed on the basis of the model in which the crystalline and amorphous phases are combined in series and parallel along the chain axis. The analysis shows that e
15 in the crystalline phase decreases considerably above the primary dispersion temperature, whereas e
24 in the crystalline phase increases with increasing temperature.
Electron Microscopy Study of ScMnO3
Authors: Nakano Hiromi , Maeda Takashi , Xu H. W. , Kamegashira Naoki , Enami Kazuyuki
Published: October 2002

We observed high-resolution transmission electron microscopy (HRTEM) images of ScMnO3 under the conditions E=400 kV and C
s=1.0 mm, and attempted computer simulations of the images using the multislice method, the results of which strongly support the X-ray Rietveld analysis in our previous study.
Stability and Chaotic Motions of a Symmetric Heavy Gyroscope
Authors: Zheng-Ming Ge Zheng-Ming Ge , Hsien-Keng Chen Hsien-Keng Chen
Published: October 2002

The nonlinear motion of a symmetric heavy gyro mounted on a vibrating base, particularly its long-term dynamic behavior for a wide range of parameters, is investigated. The system exhibits both regular and chaotic motions. Two typical routes to chaos, namely through period-doubling and intermittency, are found in this study. The method of multiple scales is used to analyze the responses and to determine the stability of the trivial fixed point for the system excited by single harmonic force. The stability of the system excited by multiple harmonic forces has been studied by Lyapunov's direct method. As the system is subjected to external disturbance, the Melnikov method is used to show the existence of chaotic motion. The effect of the number of forcing frequencies on the chaotic regions is also established. The numerical results, in which the existence of chaos is demonstrated, are presented in the form of bifurcation diagrams, phase portraits, Poincaré maps, and Lyapunov exponents. The effect of the gyroscope's spinning speed is also studied. It is found that increasing the gyroscope's spin speed is the simplest method to overcome the chaotic motion for this system.
Numerical Study of Single-Electron Resonant Tunnelling via a Few Ionised Donors in Laterally Confined Resonant Tunnelling Diodes
Authors: Hiroshi Mizuta Hiroshi Mizuta
Published: October 2002

Single-electron resonant tunnelling (RT) assisted by a few ionised donors is studied for a laterally confined resonant tunnelling diode. The 3D multimode scattering matrix (S-matrix) theory is adopted, introducing the discrete scattering potential of background donors in the active device region. With a few ionised donors placed in the device region, the calculated transmission rate clearly shows new resonances which are dependent on the donor configuration. Visualisation of the electron probability density reveals that these resonances originate in RT via single-donor-induced localised states. This new type of RT leads to I-V characteristics with current steps of the order of 0.1 nA per donor before the main current peak, which are in good agreement with experimental results. In addition, the donor-position dependence of the current plateaux and the donor-induced asymmetry of the fine structures are demonstrated.
Thickness Dependence of H Radical Treatment of Si Thin Films Deposited by Plasma-Enhanced Chemical Vapor Deposition Using SiF4/SiH4/H2 Gases
Authors: Tatsuru Shirafuji Tatsuru Shirafuji , Hisao Kondo Hisao Kondo , Kunihide Tachibana Kunihide Tachibana
Published: October 2002

Thickness dependence of H radical treatment of silicon thin films deposited using SiH4/H2 and SiF4/SiH4/H2 plasmas has been investigated. In both cases, H radicals have caused etching and crystallization. In the case of films less than 60 Å thick, almost pure etching occurred. In the case of films more than 600 Å thick, a crystallized layer under a roughened layer remained after etching. These results indicate that crystallization effect occurs in deeper layers than those in which etching occurs.
Kinetic Model for Photochemical Processes of Laser Chemical Vapor Deposition of SiC
Authors: Toru Mizunami Toru Mizunami , Naotake Toyama Naotake Toyama
Published: October 2002

The photochemical processes in a mixture of Si2H6 and C2H2 irradiated with an ArF excimer laser (193 nm) are analyzed numerically using rate equations. The simulation includes 19 processes of photolysis, chemical reactions, and optical emission. The densities of radicals, excited atoms, etc. have been calculated as a function of time. The dependence of SiH* intensity on the laser energy is quadratic up to 10 mJ and shows saturation above 40 mJ. The Si* and C2
* intensities are proportional to the 1.3–1.7 power of the laser energy. The C2
* emission intensity of Si2H6/C2H2 mixture is higher than that of pure C2H2. These calculated results agree with the results of optical emission spectroscopy experiments. The reactions of Si* with C2H2 and C2H contribute to the increase in C2
* emission and in the deposition rate when Si2H6 is added to C2H2.
Anomaly in Sputtering on Titanium Nitride Film Growth by Post-Irradiation Processing*1
Authors: Min Kyung-youl , Suzuki Yosuke , Mitsuhashi Riichirou , Inoue Masahiko , Ryuichi Shimizu Ryuichi Shimizu , Siegfried Hohmann Siegfried Hohmann
Published: October 2002

We have developed an ultrahigh-vacuum (UHV) apparatus which enables reflection high-energy electron diffraction (RHEED), sputtering yield measurement and ion scattering spectroscopy (ISS) to be performed simultaneously, leading to a more comprehensive understanding of the growth mechanism of titanium nitride (TiN) film by post-irradiation processing. The sputtering yield measurement revealed an anomalous sputtering phenomenon in the initial stage of post-irradiation processing, i.e., sputtering hardly took place on a titanium film under 3 keV N2
+ ion irradiation for doses below ∼5×1015 ions/cm2. Further N2
+ ion irradiation led to a low sputtering yield for doses between ∼5×1015 ions/cm2 to ∼3×1016 ions/cm2, and finally approached a steady-state sputtering for doses above ∼3×1016 ions/cm2. Monitoring of the surface composition was also performed by ISS to examine whether the surface composition follows the change of the sputtering behavior or not.
Elemental Composition of Reactively Sputtered Indium Nitride Thin Films
Authors: Kumar Sunil , Li Mo Li Mo , Motlan Motlan , Trevor L. Tansley Trevor L. Tansley
Published: October 2002

Indium nitride (InN) thin films have been grown on a variety of substrates using low-temperature radio frequency reactive sputtering of indium metal in pure nitrogen plasma. Quantitative compositional analyses of the films, carried out using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS), suggest that large amounts of oxygen are present in them. The high concentration of oxygen in our films is attributed to the voided microstructure as revealed by cross-sectional scanning electron microscopy. The XPS studies also suggest that the oxygen incorporated into the films is bonded to nitrogen.
Direct Observation of Poly(macromonomer) by Scanning Tunneling Microscopy*1
Authors: Shin-ichi Unayama Shin-ichi Unayama , Ken Nakajima Ken Nakajima , Takayuki Ikehara Takayuki Ikehara , Toshio Nishi Toshio Nishi , Yasuhisa Tsukahara Yasuhisa Tsukahara
Published: October 2002

Direct observation of a single molecule of poly(macromonomer) adsorbed on a highly oriented pyrolytic graphite was carried out by scanning tunneling microscopy (STM). The poly(macromonomer) studied is multibranched polystyrene possessing very dense polystyrene side chains of uniform molecular weight, which was prepared by polymerization of polystyrene macromonomers. It was revealed that the polystyrene side chains of the poly(macromonomer) extended from the main chain and were observed as an array of parallel lines on the graphite. The interval between the side chains was estimated as 0.42±0.03 nm. This value indicates that the main chain does not have an all-trans conformation but a TG+TG- conformation of the staggered model with alternate arrangement of the side chains, although the main chain is highly extended. We also observed an intramolecular structure, i.e., phenyl groups in the side chain. The distance between the two nearest-neighbor phenyl groups in the same side chain was observed as approximately 0.30 nm, indicating that each side chain is adsorbed on the graphite surface with strong intra- and intermolecular interactions. It was also confirmed by STM that the polymerization of macromonomers took place to form poly(macromonomer) in spite of the extremely high segment density.
Impedance Measurement for Various Vacuum Components in Pohang Light Source Storage Ring
Authors: Dae-Hyun Han Dae-Hyun Han , M. Kwon M. Kwon , Young-Soo Kim Young-Soo Kim
Published: October 2002

The Pohang Light Source (PLS) is a 2 GeV, third-generation synchrotron light source which was recently commissioned. Loss factor measurements were carried out for various storage ring vacuum components using the synthetic pulse technique. The measurement was done for bunch lengths (σ
l
) ranging from 7.1 to 30 mm. The measured devices were elliptical and circular photon masks, bellows with elliptical and circular cross sections, ellipse-to-diamond transition, ellipse-to-ellipse transition, beam position monitor chamber, and circular T-piece. Broad-band impedances were obtained by fitting the measured loss factors to broad-band resonator model. The total broad-band impedance of 250 devices was 0.17 \ohm, which is a small fraction of the total machine impedance budget as expected in the calculation.
Effects of Atomic Arrangement at Tip Apex and Tip-Sample Distance on Atomic Force Microscopy Images: A Simulation Study
Authors: Masaharu Komiyama Masaharu Komiyama , Shin'ya Ohkubo Shin'ya Ohkubo , Katsuyuki Tazawa Katsuyuki Tazawa , Kazuya Tsujimichi Kazuya Tsujimichi , Akiyasu Hirotani Akiyasu Hirotani , Momoji Kubo Momoji Kubo , Akira Miyamoto Akira Miyamoto
Published: October 2002

Using a newly developed atomic force microscopy (AFM) simulator ACCESS (AFM simulation code for calculating and evaluating surface structures), effects of the atomic arrangement at the tip apex and tip-sample distance on AFM image resolution were examined. A tip which has an atom protruding at its apex and is scanning in the repulsive force range is found to be necessary for obtaining atomically resolved AFM images. The second atomic layer of the tip determines the force characteristics of the system, as well as the AFM image phase shift. Since in actual AFM systems these two effects are convoluted, it is apparent that scanning under the same applied force does not necessarily mean the same tip-sample distance or the same image resolution, unless one is sure that the atomic arrangement at the proximity of the tip apex is the same. It is also found that surface point defects mirror the atomic arrangements of the tip apex in the AFM images, both in attractive and repulsive force ranges, indicating their possible use in tip apex evaluation at the atomic level.
Decomposition of Low-Pressure Pollutant by Repeated Pulse Microwave Discharge
Authors: Kohchi Akito , Singo Adachi Singo Adachi , Yoshiro Nakagawa Yoshiro Nakagawa
Published: October 2002

Experimental results of the decomposition of CO2 and Freon-12 by repeated pulse microwave discharge in low-pressure gas are presented. With the use of this nonequilibrium plasma, the carbon dioxide was efficiently deoxidized to CO without adding a reducing agent (hydrogen). Optimum efficiency was 275 nmol/J at a pressure of 533 Pa and microwave power of 150 W. Freon-12 was decomposed in ratios of 67% (53.3 Pa) and 35% (133 Pa) by 10 s discharge. Optimum efficiency of 20 nmol/J was obtained at a pressure of 133 Pa. The optimum values should be related to the generation of high-energy electrons which were active in chemical reaction, and the amount of molecules in the reactor chamber. This process can be used as a pretreatment of low-pressure pollutant gas without adding any other gas.
Experimental Study of the Mechanism of Skiing Turns. III. Measurement of Edging Angles of Skis on Snow Surface
Authors: Ichino Toshio Sahashi
Published: October 2002

By observing the track of a sliding ski during a parallel turn on a snow plane, we clarified the relationship between the direction of the ski turn and the edging angle. The relationship was the same as that observed in the experiment using a model ski sliding on a sand plane. Namely, when the angle formed between the horizontal plane and the ski, β0, is 0°, the motion of the ski is a straight descent; when β0 \neqq0°, it is a turning descent. If we define the edging angle as β0, it is understood that the turning of the skis is determined only by the edging angle. The skier's sense of making a ski turn using his muscular strength can be explained as a matter of the perception of the skier.
Suppression of the Phase Transition to C54 TiSi2 due to Epitaxial Growth of C49 TiSi2 on Si(001) Substrates in Silicidation Process
Authors: Komiya Satoshi , Tomita Hirofumi , Ikeda Kazuto , Yoshimasa Horii Yoshimasa Horii , Tomoji Nakamura Tomoji Nakamura
Published: October 2002

The epitaxial C49 TiSi2 formed after annealing of Ti films deposited on Si(001) substrates has been studied by grazing-incidence X-ray diffraction. The relations C49 TiSi2(10\bar1)∥Si(001), C49 TiSi2(100)∥Si(001), and C49 TiSi2(010)∥Si(001) are observed on a highly BF2-implanted substrate, and the a or b face of C49 is sharply orientated toward the directions deviating ±5° from Si<110> on a clean substrate in ultrahigh vacuum (UHV). These epitaxial C49 grains are thermally stable and difficult to transform into the C54 phase even after annealing at high temperature. In contrast, ramdomly distributed C49 grains have been observed on unimplanted and low-dosed substrates and for thick Ti films in UHV. These polycrystalline C49 grains are thermally unstable and easily transformed into the C54 phase. The influence of implantation and UHV process on the growth of the epitaxial C49 and the phase transition of C49 to C54 are discussed.
Characterization of Highly Selective SiO2/Si3N4 Etching of High-Aspect-Ratio Holes
Authors: Hayashi Hisataka , Kazuaki Kurihara Kazuaki Kurihara , Makoto Sekine Makoto Sekine
Published: October 2002

The pattern size dependence of SiO2 and Si3N4 etch rates of contact holes (RIE-lag) in C4F8+CO plasma was studied. It was found that these etch rates can be characterized by the aspect ratio, regardless of the pattern size. SiO2 etch rate decreased with increasing aspect ratio and became 0 at an aspect ratio of 6. Si3N4 etch rate also decreased; however, etching still occurred at an aspect ratio of 30. From ion current measurements through capillary plates (CPs), it was deduced that etch rates decreased because of decreasing ion current. XPS analyses revealed that fluorocarbon film deposited on the Si3N4 surface at the bottom of a hole was more F-rich than that deposited on a flat Si3N4 surface. This explained why Si3N4 is etched even in high-aspect-ratio holes. A small amount of O2 addition to the C4F8+CO plasma resolved the RIE-lag. It was found that the ion current density at high aspect ratio increased with O2 addition, which would enhance SiO2 etching and contribute to suppressing RIE-lag.
Low Temperature Synthesis of Diamond Films with Electron Cyclotron Resonance Plasma Chemical Vapor Deposition
Authors: Mantei Thomas D. , Ring Zoltan , Schweizer Mark , Tlali Spirit , Jackson Howard E.
Published: October 2002

In this paper we review our previous work and present additional results on polycrystalline diamond film synthesis in a CH4/H2/O2 microwave discharge at substrate temperatures down to 300° C. Low temperature diamond growth was achieved by combining three strategies: the low temperature limit for diamond growth was reduced by decreasing the total gas pressure in the deposition chamber to 1–3 Torr; low pressure diamond growth was enhanced by applying a static axial magnetic field to the plasma generation region to increase gas dissociation and ionization in the Torr pressure range; and the microwave input power was pulse modulated to control the relative fluxes of neutral atomic hydrogen and charged positive ions to the substrate. With these combined methods, high quality diamond films exhibiting a clearly defined Raman phonon peak could be grown at backside substrate temperatures from 300° C to 500° C.
Metalorganic Chemical Vapor Deposition of Complex Metal Oxide Thin Films by Liquid Source Chemical Vapor Deposition
Authors: Buskirk Peter C. Van , Bilodeau Steve M. , Jeffrey F. Roeder Jeffrey F. Roeder , Peter S. Kirlin Peter S. Kirlin
Published: October 2002

The implementation of ferroelectric thin films in advanced semiconductor devices is near; facile integration at ULSI geometries requires chemical vapor deposition (CVD) process technology. The low volatility and thermal stability of many of the existing source reagents has driven the development of liquid source CVD, in which composition is set by volumetric metering of liquids followed by flash vaporization. The methodology as well as early results for Ba1-
x

Sr

x

TiO3, Pb1-
x

(La

x

Zr1-
y

Ti

y

)1-
x
/4O3 and SrBi2Ta2O9 thin films, which are among the best reported for any deposition method, will be reviewed. These results establish liquid source CVD as a leading candidate to become the predominant deposition technology enabling the integration of ferroelectric thin films in ULSI devices.
Limiting Process for Gold In-Diffusion in Silicon with and without Extended Defects
Authors: Masami Morooka Masami Morooka
Published: October 2002

Gold was in-diffused at 1150° C into silicon containing extended defects (dislocations or stacking faults) and into defect-free silicon single crystals, and the diffusion-limiting process for the gold in-diffusion was investigated. Gold diffusion in the crystals without defects and that very near the specimen surface in crystals with defects are limited by the diffusion of self-interstitials to the surface. Diffusion in the crystals with defects is limited by the diffusion of interstitial gold atoms from the surface. In crystals with an extremely low concentration of extended defects, the diffusion is limited by the diffusion of self-interstitials to the defects.
Influence of Chamber Pressure on Optoelectronic and Structural Properties of Boron-Doped Hydrogenated Silicon Films Prepared by RF Magnetron Sputtering
Authors: Das Debabrata , Sharma S. N. , Banerjee D. , A. K. Barua A. K. Barua , Ratnabali Banerjee Ratnabali Banerjee
Published: October 2002

Results on the characterisation of boron-doped hydrogenated silicon films prepared by rf magnetron sputtering technique are presented. The effects of chamber pressure on the structure and electronic properties of the films were investigated. The films were characterised by conductivity and thermoelectric power measurements, optical absorption and reflectance (specular and diffuse) measurements, X-ray diffraction analysis, infrared vibrational spectroscopy, Raman spectroscopy and scanning electron microscopy. The structural characteristics were correlated with the conductivity and thermoelectric power. With increase in pressure the growth pattern changed from an amorphous one, with poor structural and optoelectronic properties, to one which was crystalline, with improved structural ordering. In the intermediate range of pressure growth was mainly expected to be governed by BH3 radicals. With further increase in pressure, segregation of boron atoms with concomitant deterioration in crystalline structure was observed. The features were however distinct from those of the amorphous films obtained at low pressures probably due to the increased role of atomic hydrogen at higher pressures.