bluuebunny/crossref_metadata_2025 huggingface dataset:
An Improved In0.5Ga0.5P/GaAs Double Heterostructure-Emitter Bipolar Transistor Using Emitter Edge-Thinning Technique
Authors: Lin Yu-Shyan , Wu Yu-Huei , Su Jan-Shing , Hsu Wei-Chou , Lin Shing-Dong Ho
Published: October 2002

An improved In0.5Ga0.5P/GaAs double heterostructure-emitter bipolar transistor (DHEBT) has been fabricated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The 100 Å undoped GaAs spacers grown on both sides of the base are used to improve the recombination of p-n interface and to increase the common-emitter current gain. The emitter edge-thinning technique is used to reduce the surface recombination current and improve the current gain. A current gain of 180 with an offset voltage as low as 60 mV are achieved. Meanwhile, Gummel plot is shown to understand the composition of collector and base currents.
Enhancement of the Breakdown Voltage of GaAs/AlxGa 1-xAs Heterostructures for GaAs Metal-Semiconductor Field Effect Transistors Grown by Metalorganic Chemical Vapor Deposition
Authors: Mohri Mikio , Kakinuma Hiroaki , Takashi Ueda Takashi Ueda , Masahiro Akiyama Masahiro Akiyama
Published: October 2002

We have studied enhancement of the breakdown voltage (B
V) of epitaxial structures for GaAs metal-semiconductor field effect transistors (MESFETs) using GaAs/Al

x

Ga1-
x

As heterostructures grown by metalorgnic chemical vapor deposition (MOCVD). The breakdown voltage (B
V
i) between FETs (lateral isolation) and the breakdown voltage (B
V
sub) of the epitaxial structure between FETs and substrates (vertical isolation) were mainly studied. The dependence of B
V on the thickness (d), hole concentration (N
A), AlAs mole fraction (x=0.3–1.0) of Al

x

Ga1-
x

As layers and the ambient temperature (T= RT–200° C) was investigated. B
V is much higher in the range of x>0.6. B
V
i and B
V
sub are maximum at 86.5 V and 30 V at 200° C in the case of x=0.8, respectively. The enhancement of B
V is attributed to a drastic decrease in N
A with increasing x. The GaAs MESFETs were fabricated using an optimized epitaxial structure with an Al0.8Ga0.2As buffer layer. The drain current-drain voltage (I
D–V
D) characteristics at 200° C are superior to those at RT. Avalanche breakdown of I
D did not occur at V
D of less than 5 V.
Effect of a Buffer Layer on the Surface Acoustic Wave Characteristics of Pb(Zr, Ti)O3 Film/Buffer Layer/Semiconductor Substrate Structures
Authors: Wen-Ching Shih Wen-Ching Shih , Mu-Shiang Wu Mu-Shiang Wu
Published: October 2002

The effect of a buffer layer on the surface acoustic wave properties of Pb(Zr, Ti)O3 (PZT) film/buffer layer/ semiconductor substrate structures was examined theoretically. Large coupling coefficients (2.8–3.4%) can be obtained when the interdigital transducer (IDT) is on top of the PZT film, with (type 4) and without (type 3) the floating-plane electrode at the PZT film-buffer layer interface. In the type 4 IDT configuration, there exists a minor peak of the coupling coefficient when the h
K value of the PZT film is about 0.3. The minor peak values of the coupling coefficient (0.62–0.93%) decrease when we increase the thickness of the buffer layer from 0 to 0.25. These results could be useful for the further development of ferroelectric devices, semiconductor devices and SAW devices on the same substrate.
A Novel Thin-Film Transistor with Vertical Offset Structure
Authors: Lin Chiung-Wei , Chang Chun-Yen
Published: October 2002

A novel device structure consisting of conventional hydrogenated amorphous silicon (a-Si:H) for the source and drain and of hydrogenated microcrystalline soilicon ( µc-Si:H) for the channel region which can improve the performance of thin-film transistors (TFTs) has been proposed and fabricated. Undoped a-Si:H serves as a blocking layer to suppress the OFF-state current in the drain region which is comparable to that of conventional a-Si:H TFT with a much higher drivability. The fabrication process is simple and inexpensive with the possibility of high reliability.
Possibility of Realizing a Gas Sensor Using Surface Conductive Layer on Diamond Films
Authors: Sung Gi Ri , Ishikawa Tomoya , Tanaka Seiichi , Kimura Tetsuo , Yukio Akiba Yukio Akiba , Masamori Iida Masamori Iida
Published: October 2002

The electrical surface resistance of diamond films deposited by the hot-filament chemical vapor deposition (CVD) method is measured in oxidizing and reducing atmospheres. The electrical surface resistance decreases in NO2, HCl and O3 gases. On the other hand, it increases in NH3 gas. The mechanism of change in electrical resistance is explained by the formation mechanism of a p-type surface conductive layer. The realization of a gas sensor will be discussed considering the experimentally obtained results.
In Situ Optical Diagnosis of Pulsed Laser Deposition and Oxidation of YBa2Cu3O7-δ Thin Films
Authors: Kanda Naoki , Kawasaki Masashi , Nakano Kenichi , Shiraishi Tadashi , Akihiro Takano Akihiro Takano , Hideomi Koinuma Hideomi Koinuma
Published: October 2002

Laser light (670 nm) was polarized and impinged on YBa2Cu3O7-δ (YBCO) films during their growth by pulsed laser deposition and subsequent oxidation. By simulation of the light reflectance variation, the refractive index (n) and extinction coefficient (k) of the growing films were determined together with the deposition rate. A reflectance change was also observed during cooling the deposited films and was attributed to the increase in oxygen content in the film by comparison with ex situ X-ray diffraction data. Furthermore, the ortho-tetra phase transition could be detected in situ by this method. Thus, the reflectance measurement of p-polarized light was verified to enable in situ characterization of optical properties and oxygen nonstoichiometry of oxide films during their pulsed laser deposition.
Study on Ultrafast Dynamic Behaviors of Different Nonlinear Refractive Index Components in CS 2 Using a Femtosecond Interferometer
Authors: Yasuhiro Sato Yasuhiro Sato , Ryuji Morita Ryuji Morita , Mikio Yamashita Mikio Yamashita
Published: October 2002

We investigated time responses of components parallel n
2 /\kern-2p
t/ (t) and perpendicular n
2 ⊥(t) to pump polarization of the nonlinear refractive index in CS2 and its dilute solutions using a femtosecond time division interferometer. The temporal profiles of n
2 /\kern-2p
t/(t) and n
2 ⊥(t) were decomposed into the electronic, fast- and slow-decay nuclear contributions based on the response time. The magnitudes, signs and time constants of these three contributions of n
2 /\kern-2p
t/(t) and n
2 ⊥(t) were also evaluated with high accuracy. Moreover, the n
2 /\kern-2p
t/ (t) and n
2 ⊥(t) measurements in the dilute CS2 solutions showed that the ratio between the fast-decay contributions of time responses of n
2 /\kern-2p
t/ (t) and n
2 ⊥ (t) was the same value as that between the slow-decay contributions. This result is explained using a cluster model.
High-Order Transverse Mode Characteristics of 790 nm Vertical-Cavity Surface-Emitting Lasers
Authors: Ahn Jung Chak , Kang Hwa Young , Son Nak Jin , Park Byung Hoon , Kwak Kyu Sub , Lee Young Hee , O'Dae Kwon O'Dae Kwon
Published: October 2002

High-order polarization and transverse modes of one-step metal-organic vapor-phase epitaxy (MOVPE)-grown vertical-cavity surface-emitting laser (VCSEL) diodes are investigated. We find radially symmetric multipole transverse modes with a fixed polarization state parallel to a <110> crystal axis under room temperature CW conditions.
Polarization and Dipole Moments of Manganese-Modified Potassium Sodium Strontium Barium Niobate Crystals
Authors: Xia H. R. , Wang C. J. , Yu H. , Chen H. C. , Wang M.
Published: October 2002

The crystal growth, the ferroelectric hysteresis loops, and the infrared reflectivity spectra of manganese-modified potassium sodium strontium barium niobate (KNSBN) single crystals are reported. Compared with the undoped KNSBN crystals, the manganese-modified crystals have stable hysteresis loops, whose spontaneous polarization is about 0.18 C/m2and coercive field strength is about 600 V/mm, but those of the undoped KNSBN crystals are about 0.04 C/m2and 530 V/mm, respectivery. The experimental results of the infrared reflectivity spectra show that the infrared reflectivities vary as the orientations of the dipole moments. Thec-axis becomes the stablest orientation of the dipole moments owing to the manganese doping, and the polarization will be locked and not recede if the manganese-modified crystals are polarized into mono-domain.
Electrical Properties of Sol–Gel Deposited BaTiO3 Thin Films on Si(100) Substrates
Authors: Cho Chae Ryong , Kwun Sook Il , Noh Tae Won , Min Su Jang Min Su Jang
Published: October 2002

The electrical properties of sol–gel deposited BaTiO3 thin films on Si(100) and SiO2-buffered Si(100) substrates were investigated. The dielectric constant measured as a function of frequency was fitted using the space charge relaxation model. The effective dielectric constant (ε') and dissipation factor (tan
δ) were determined in the accumulation region from the results of capacitance–voltage ( C–V ) measurements at room temperature, at 1 MHz. Values of 23–185 and 0.02–0.08 were determined, respectively. The density of the interfacial surface states (N
ss), calculated from the width of the memory window of the C–V curve, was of the order of 1011–1012 eV-1 cm-2. The leakage current densities for BaTiO3 films deposited on Si and SiO2-buffered Si substrates were 22–57 nA/ cm2 and 0.85–4 nA/ cm2, respectively, at an applied field of 100 kV/cm. The dielectric breakdown strength exceeded 1 MV/cm for all films.
Polarization Measurement of Novel Liquid Crystals with Tetrafluorobiphenylene
Authors: Xian-Shan Wang Xian-Shan Wang , Jianxun Wen Jianxun Wen
Published: October 2002

Ferroelectricity and spontaneous polarization of two compounds were investigated by plotting polarization versus electric field with a sine waveform in conjunction with other conventional methods such as optical polarizing microscopy and differential scanning calorimetry. The compounds are 4′-[(s)-2-methylbutoxycarbonyl] phenyl 4-(4′-n-nonyloxy-2,3,5,6-tetrafluorobiphenyl-1-ethynyl) benzoate and 4′-[(s)-2-methylbutoxycarbonyl] phenyl 4′′-[(4-n-nonyloxy-2,3,5,6-tetrafluorophenyl) ethynyl] benzoate. They show polarizations of 8.9 and 12.6×10-6 C/m2 and tilt angles of 9.2 and 20° at the temperature at which 10° C below their curie point, respectively. The curie point, that is, the mesophase transition between the smectic A and the chiral smectic C phases occurs, was identified from the polarization versus electric field hysteresis, and a ferroelectric phase temperature range of 108° C was found in these materials.
Effect of Additive Elements on Amorphization in M75C25 (M=Fe, Co or Ni) and Fe80N20 Systems by Mechanical Alloying
Authors: Keisuke Omuro Keisuke Omuro
Published: October 2002

Mechanical alloying (MA) of elemental powder mixtures of the M75-
x

A

x

C25 system (at.%) (M=Fe, Co or Ni; A=Ti, V, Cr, Mn, Fe, Co or Ni) with x=0 and 20 is performed using a planetary ball mill. In the MA processing, the A additives with a negative value of the interaction parameter W
AC
M, such as Ti and V, markedly promote solid-state reactions in the MA products, leading to their amorphization, in contrast to the additives with a positive W
AC
M value such as Co and Ni in Fe–C systems; the parameter W
AC
M represents the difference in bonding energy of A–C atomic pairs (E
AC) and M–C pairs (E
MC) in the ternary M–A–C solution, i.e. W
AC
M=E
AC-E
MC. Such effects of additives seen for M–C materials are also true of experimental results of MA of Fe64A16N20 (A=Cr or Nb) materials with a negative interaction parameter W
AN
Fe.
Cross-Sectional Observations of Laser Addressed UV Curable Smectic Liquid Crystal Cells
Authors: Rumiko Yamaguchi Rumiko Yamaguchi , Shin Masuda Shin Masuda , Susumu Sato Susumu Sato
Published: October 2002

Cross-sectional images of a laser addressed smectic liquid crystal (SmLC) are successfully observed using a UV curable SmLC. Profiles of a light scattering focal conic texture in a homeotropically aligned SmLC are clarified for different laser scanning speeds.
Cross-sectional High-Resolution Transmission Electron Microscope Study of Heteroepitaxial Diamond Film Grown on Pt Substrate
Authors: Zhou Guofu , Tarutani Masayoshi , Yoshizo Takai Yoshizo Takai , Ryuichi Shimizu Ryuichi Shimizu
Published: October 2002

Heteroepitaxial diamond film grown on Pt(111) was studied by cross-sectional high-resolution transmission electron microscopy (HRTEM). It is found that the interface has a complicated structure including a thick layer of graphite and many small Pt fragments. The epitaxial growth of diamond on Pt substrate is confirmed to be effective with a relationship of diamond{111}//Pt{111} and diamond<110>//Pt<110>. A high-resolution image of the interface between diamond and Pt reveals that diamond particles directly connect with Pt in the absence of an intermediate layer. In some areas, graphite also shows a structural relationship with the Pt substrate and diamond. The graphite(0001) planes tend to be formed parallel to the Pt surface. A high-resolution image of the interface between graphite and diamond shows graphite(0001)//diamond(111) with three diamond(111) planes matching up with two graphite(0001) planes. Some possible heteroepitaxial and nucleation mechanisms are discussed.
The Electron-Spin Resonance Spectrum of Diamond Film Synthesized by Chemical Vapor Deposition
Authors: Watanabe Ichiro , Kousei Sasaki Kousei Sasaki , Taku Hamaoka Taku Hamaoka
Published: October 2002

The electron-spin resonance (ESR) spectrum of diamond films of high quality and free-standing form was investigated. The ESR spectrum of diamond film has been believed to be composed of a main line and two shoulders. The main line has been attributed to a superposition of two components at two different phases in the film. We found that the spectrum is composed of a slightly asymmetric line and two shoulders. The shape of the asymmetric line did not change even when the film was etched by an oxygen plasma so that the thickness of the film was halved. We propose that the main line can be attributed to a single component with an anisotropic g tensor of axial symmetry.
Solid-Phase Reactions in Polymorphic Epitaxial Contact Systems of bfAl/YSi2-x/Si
Authors: Fukuda Tomoyuki , Mayumi Takeyama Mayumi Takeyama , Atsushi Noya Atsushi Noya
Published: October 2002

Solid-phase reactions taking place in an epitaxial Al/YSi2-
x

/Si contact system are examined by X-ray diffraction and depth profiling using Auger electron spectroscopy. The diffusion of Al into YSi2-
x

and the subsequent reaction between Al and Y forming Al3Y take place after annealing for 1 h at 400 and 450° C, respectively. Although an out-diffusion of Si and Y leads to failure of the contact system, the distribution of Al is restricted to within the initially formed YSi2-
x

layer without forming Al spikes.
Titanium Nitride Thin Films Epitaxially Grown by N-Implantation
Authors: Yoshitaka Kasukabe Yoshitaka Kasukabe , Atsuyuki Ito Atsuyuki Ito , Shinji Nagata Shinji Nagata , Mokuyoshi Kishimoto Mokuyoshi Kishimoto , Yutaka Fujino Yutaka Fujino , Sadae Yamaguchi Sadae Yamaguchi , Yukio Yamada Yukio Yamada
Published: October 2002

The epitaxial growth of titanium nitride (TiN) films, formed by implanting nitrogen ions (N2
+) with 62 keV into 100-nm-thick Ti films grown on NaCl substrates held at 250°C, has been studied mainly by transmission electron microscopy. It has been revealed that (001)-oriented TiNy is epitaxially grown by N-implantation into the as-grown (03·5)-oriented hcp-Ti. The nitriding mechanism of epitaxial Ti thin films is discussed.
Axial Dependence of Electron Energy Distribution in Symmetrically RF Ar Discharges
Authors: Takashi Kimura Takashi Kimura , Kouji Kaga Kouji Kaga , Kazuyuki Ohe Kazuyuki Ohe
Published: October 2002

Axial dependence of the electron energy distribution function (EEDF) is measured with a Langmuir probe in symmetrically capacitively coupled RF (13.56 MHz) Ar discharges while keeping the RF current constant at 150 mA. The bulk of the EEDF in low-pressure discharges depends on the DC ambipolar potential, while its tail on the local electric field. The average electron energy and the electron density decrease toward the electrode.
Electromagnetic Radiation due to Thermal Agitation in a D-Band Cavity
Authors: Shigemi Inagaki Shigemi Inagaki , Eizi Ezura Eizi Ezura , Masaaki Kobayashi Masaaki Kobayashi , Kimio Morimoto Kimio Morimoto
Published: October 2002

At resonant frequencies in a microwave cavity, electromagnetic radiation is induced due to thermal agitation. We investigated the TM010 mode of a D-band cavity at room and liquid nitrogen temperatures. We assumed that the power spectrum is Lorenzian and that the integral of the spectrum is equal to the expectation energy of a single degree of freedom. Using the coupling constants, measured with a network analyzer, and the Johnson-Nyquist noise as a reference power level, we evaluated the absolute value of the radiation at room temperature. The measured peak value was almost half the expected value. The disagreement can partly be explained in terms of an equivalent temperature which can be different from the physical temperature. This experiment was made possible through the adoption of a cooled high-electron-mobility-transistor (HEMT) amplifier and parallel band-pass filters.
High-Emittance and Low-Brightness Electron Gun for Reducing-Image Projection System: Computer Simulation
Authors: Mamoru Nakasuji Mamoru Nakasuji , Hiroyasu Shimizu Hiroyasu Shimizu
Published: October 2002

The required electron gun characteristics for a reducing-image projection system so that the emittance is much larger than 187 µ m· mrad and the brightness is variable around 7.3×104 A/cm2 sr are estimated. For an electron gun with flat cathode, Wehnelt, control-anode and anode electrodes, an emittance of more than 1000 µ m· mrad is obtained by optimization of the cathode to control anode distance, the control-anode radius and the Wehnelt electrode shape. The brightness is variable from 3.9×104 to 9×104 A/cm2 sr by control of the control-anode voltage. The optimum control-anode radius increases and the brightness tends to decrease with increasing cathode to control-anode distance. The angle between the beam edge and Wehnelt electrode is optimum at about 62°, which is smaller than the well-known 67.5° in a Pierce-type electron gun.
Amorphous Se 75Ge 25 Resist Profile Simulation of Focused-Ion-Beam Lithography
Authors: Hyun-Yong Lee Hyun-Yong Lee , Hong-Bay Chung Hong-Bay Chung
Published: October 2002

The two- and three-dimensional (2D and 3D) development profiles of an amorphous Se75Ge25 thin film, which acts as a positive resist in focused-ion-beam (FIB) lithography, are simulated using a simplified development model. For the Monte Carlo (MC) simulation, both the depth and the lateral distance in resist are divided into discrete cubic pixels of 25 ×25 ×25 Å, and then the energy densities deposited by the exposure of a FIB with a diameter of 0.2 µm, an incident energy of 80 keV and a fixed dose of 1.1 ×1015 ions/cm2, are summed up in these pixels. For the development condition of the HCl+HNO3+H2O solution in the ratio 1:1:3 at 25°C, the exposed region in the Se75Ge25 resist is markedly etched for 2T to 3T, in which T represents a normalized development time for applying the various doses and energies and corresponds to 2.1 s under the above-mentioned exposure conditions. For 3D simulation, the developed pattern widths are 0.200, 0.220 and 0.225 µm for 2T, 4T and 6T, respectively. The slope of developed walls is nearly constant throughout the entire depth range, and the development rate is decreased compared with the 2D case. Under this exposure condition, 4T was chosen as a reasonable development time.
Ultrasonic Visualization of Still and Flowing Waters Using Contrast Agents of Magnetite-Encapsulated Porous Silica Microspheres
Authors: Zhang Minjuan , Tomoyuki Itoh Tomoyuki Itoh , Masanori Abe Masanori Abe
Published: October 2002

Porous silica microspheres, ∼2.2 µm in average diameter, were encapsulated with magnetite ( Fe3O4) by ferrite plating in an aqueous solution of FeCl2 at 65°C. Using the resultant ferrite-encapsulated particles as ultrasonographic contrast agents (in which air trapped in the pores scatters ultrasonic waves), we tried to visualize still and flowing waters in holes and a channel perforated in agar blocks using a 7.5 MHz B-mode echograph. Clear image enhancement was successfully obtained only when the ferrite-encapsulated particles were evaporated before they were dispersed in the water. This is because during ferrite plating in the aqueous solution the pores were permeated with water, which was expelled by evaporation, and then substituted by air when the particles were again exposed to air.
Effect of Case Sample Difficulty and Choice of Rating Scales on Interobserver Variability in Receiver Operating Characteristic Experiments
Authors: Shiraishi Junji , Utsunomiya Akane , Masaru Yamasaki Masaru Yamasaki , Katsuhisa Tanaka Katsuhisa Tanaka
Published: October 2002

We evaluated the effect of case sample difficulty in receiver operating characteristic (ROC) experiments using both discrete and continuous rating scales, and by analyzing data from the same set of observers at three different levels of image-reading difficulty. Simulated computed radiographic mammograms were used as case samples. Our experimental results show that the averaged A

z
values were essentially identical with both rating scales. When we used the continuous scale, the significance levels tended to be lower than those with the discrete scale, raising the possibility that tests based on the continuous scale may be more statistically valid.
A Synthetic Approach to RF Plasma Modeling Verified by Experiments: Demonstration of a Predictive and Complete Plasma Simulator
Authors: Evangelos Gogolides Evangelos Gogolides
Published: October 2002

True predictive models of plasma etching or deposition processes are rare today, due to the complexity of such processes, and the continuous change of plasma equipment. Modeling efforts concentrate only on part of the whole problem, e.g. on the plasma physics, or on topography evolution. The modeling approach reviewed here first analyses the plasma in modules, such as the plasma physics, the plasma chemistry, and the surface chemistry, and then attempts their synthesis into a complete plasma simulator with predictive capabilities. The interactions among modules are taken into account, and iterative solution procedures show that the complete simulator quickly converges to a consistent solution, which shows substantial differences with the solution obtained without any interactions. The complete plasma simulator is applied for rf plasmas in CF4, and CH4, used respectively for the etching of Si and the deposition of Diamond-Like Carbon. Predictions of neutral densities and etching/deposition rates compare successfully with experimental data.
Mechanism of AlCu Film Corrosion
Authors: Siozawa Ken-itiro , Fujiwara Nobuo , Hiroshi Miyatake Hiroshi Miyatake , Masahiro Yoneda Masahiro Yoneda
Published: October 2002

We report corrosion of an Al–Cu film treated by O2/CF4 downflow. Corrosion occurs on the Al–Cu surface in the case of a P-SiN film deposited on a TiN/Al–Cu film, but does not occur in the case of deposition of a P-SiO2 film or no film on TiN. In ion-chromatography analysis, the NH4
+ concentration of the sample treated by O2/CF4 downflow was more than twice that for a sample not treated by O2/CF4 downflow. In TDS analysis, the peak signal of NH3 from a P-SiN film treated by O2/CF4 downflow was observed at around 150° C. These results indicate that NH3 molecules desorbed from the P-SiN film adsorb on the Al–Cu surface, and corrosion of the Al–Cu film is induced by chemical reaction between NH3 and Al–Cu. We also investigated the reducing effect of corrosion by O2 downflow treatment and DI water rinsing. The NH3 concentration on the wafer decreases to about half the initial value following these treatments. Consequently, the outbreak of corrosion is reduced.
Etching Characteristics of WSi2 with Pulsed-Electron Cyclotron Resonance Plasma
Authors: Fujiwara Nobuo , Maruyama Takahiro , Satoshi Ogino Satoshi Ogino , Masahiro Yoneda Masahiro Yoneda
Published: October 2002

Etching properties of WSi2 are investigated with pulsed-electron cyclotron resonance (ECR) plasma. A new type of charge-induced notch, which appears at an inside line, has been discovered in polycide etching. By comparing the notch properties to reactive ion etch (RIE) lag characteristics, the deposition of a conductive film on the sidewall is suggested as the origin of the electrons. The RIE-lag is improved with pulse plasma due to a reduced dissociation of reaction byproducts. The dissociation of byproducts produces a large amount of tungsten. The actual quantity depends on the duty ratio of the pulse modulation, and continuous discharge is the worst case. The formation of volatile byproducts with pulse plasma also effectively reduces RIE-lag. The volatile byproducts are formed during afterglow, which produces an electron temperature lower than the W–Cl bond strength.
Reduction of Charge Build-up with High-Power Pulsed Electron Cyclotron Resonance Plasma
Authors: Maruyama Takahiro , Fujiwara Nobuo , Satoshi Ogino Satoshi Ogino , Masahiro Yoneda Masahiro Yoneda
Published: October 2002

Local side etch is one of the most significant problems in high-density plasma and low energy processing. In this paper, we report a detailed analysis of etching characteristics under various modulations and microwave conditions to achieve simultaneously no local side etch, a high etch rate and a high selectivity. In addition, we discuss the mechanism of the reduction of local side etch using a new method to estimate charge build-up.
Spectroscopic Ellipsometry of SIMOX (Separation by Implanted Oxygen): Thickness Distribution of Buried Oxide and Optical Properties of Top-Si Layer
Authors: Jayatissa Ahalapitiya Hewage , Yamaguchi Tomuo , Masahiro Nasu Masahiro Nasu , Mitsuru Aoyama Mitsuru Aoyama
Published: October 2002

Spectroscopic ellipsometry has been used to characterize SIMOX (separation by implanted oxygen) wafers. High-dose SIMOX wafers with 450 nm thick buried SiO2 were measured using a four-zone null spectroscopic ellipsometer in a 230–840 nm range. The measured spectra of Ψ and Δ were analyzed based on a multilayer structure of air/surface- SiO2/top-Si/buried- SiO2/Si in which the optical constants of the top-Si layer were analyzed using the optical constants of bulk-Si and also using model dielectric functions proposed for Si. In the fitting of Ψ and Δ spectra, a thickness fluctuation of buried- SiO2 was considered with an arbitrary thickness distribution function. Measured Ψ and Δ spectra could be well fitted under the assumption of thickness distribution in the buried- SiO2. To examine the thickness dependence of the optical properties of the top-Si layer, the thickness of this layer was systematically reduced by repeating oxidation and etching with HF. It was found that the optical constants of the top-Si layer were equal to those of Si for a thickness above 5 nm.
High-Frequency Response of Intersubband Infrared Photodetectors with a Multiple Quantum Well Structure
Authors: Victor Ryzhii Victor Ryzhii , Irina Khmyrova Irina Khmyrova , Maxim Ryzhii Maxim Ryzhii
Published: October 2002

We have theoretically studied the response of quantum well intersubband photodetectors to high-frequency modulated infrared radiation. The small-signal responsivity dependent on the modulation frequency of infrared radiation and device parameters has been derived using the proposed analytical model. It has been shown that with increasing modulation frequency the roll-off of the small-signal responsivity is associated with the electron transit and capture effects which limit the device bandwidth.
Cellular-Automaton Circuits Using Single-Electron-Tunneling Junctions
Authors: Wu Nan-Jian , Noboru Asahi Noboru Asahi , Yoshihito Amemiya Yoshihito Amemiya
Published: October 2002

We propose cellular automaton circuits that use single-electron-tunneling circuits (SET-CA). The unit cell consists of four intrinsic semiconductor islands and four single-electron-tunneling junctions. The dielectric constant of the intrinsic semiconductor is much larger than that of the junction insulator. The unit cell is charged with two single electrons. Polarization states of the two single electrons in the unit cell can be used to encode a binary signal. We designed various binary logic SET-CA circuits, and analyzed their operation by computer simulation. It was demonstrated that the SET-CA circuits having appropriate arrangements of the cells can perform correct signal transmission and elemental logic operations such as NOT, NAND, and NOR.
Cross-Contamination from Etching Materials in Reactive Ion Etcher
Authors: Yoshiharu Ozaki Yoshiharu Ozaki , Masakatsu Kimizuka Masakatsu Kimizuka
Published: October 2002

This paper reports the necessity of dedicating a reactive ion etching system for SiO2 according to etching materials. Silicon wafers etched with TiN-, Ti- or Al-coated wafers were analyzed using total reflection X-ray fluorescence and secondary ion mass spectroscopy. The amount of contamination varied with distance from the metal coated wafers. Si etched after removing the metal-coated wafers were then analyzed. Contamination was also detected, though it decreased with increasing discharge time. The contamination is believed to be due to the collisions of reaction products with reactive gas molecules and redeposition of those products onto the cathode. The contamination is decreased to detection limit by dipping into a diluted HF solution. However, the carrier lifetime of the etched wafer is severely affected by contamination less than detection limit.
Sickle Mutually Pumped Phase-Conjugate Mirror: Theoretic and Experimental Demonstration
Authors: Zhang Liangmin , Lu Jianren , Zhang Jingwen , Shao Zongshu , Chen Jun , Mu Xiaodong , Chen Huanchu , Jiang Minhua , Zhang Wanlin , Zhang Guangyin
Published: October 2002

A new mutually pumped phase conjugator with a photorefractive copper-doped potassium sodium strontium barium niobate crystal is demonstrated, in which the beams travel along a geometric path similar to the outline of a sickle. The maximum reflectivity is as high as 168%. Phase-conjugate images are obtained. The two-interaction region theory, based on the coupled plane wave amplitude, is used to account for the main characteristics of the new phase conjugator. The threshold coupling strength which depends on the reflection loss and the incident beam ratio, is also investigated and calculated.
Resistance to External Optical Feedback of Low-Chirp Strained-Quantum-Well Complex-Coupled Distributed-Feedback Laser
Authors: Wang Chi-Yu , Chuang Zuon-Min , Liao H. H. , Lin Wei , Tu Yuan-Kuang , Lee Ching-Ting
Published: October 2002

Resistance to the optical feedback of complex-coupled DFB lasers with current blocking grating was studied experimentally. The measured relative intensity noise of the lasers was as low as -160 dB/Hz even in the presence of an external feedback level of -15 dB. The modulation chirping of the device was quite small with a linewidth enhancement factor α of 1.9 measured using a fiber-response peaks method. A transmission experiment was performed over a 235 Km standard nondispersion-shifted fiber at 2.488 Gbps by direct modulation without using an optical isolator, and the power penalty was only 1.55 dB at a bit error rate of 10-12.
High Gain and High Power Organic Dye-Doped Polymer Optical Fiber Amplifiers: Absorption and Emission Cross Sections and Gain Characteristics
Authors: Tagaya Akihiro , Kobayashi Takeyuki , Nakatsuka Shiro , Nihei Eisuke , Sasaki Keisuke , Koike Yasuhiro
Published: October 2002

Amplification of high signal gain (36 dB, approximately 4000 times) and high output power (1200 W) was achieved in a Rhodamine B (RB)-doped graded-index (GI) polymer optical fiber amplifier (POFA) based on a prediction in which absorption and emission cross section data were used. The absorption and emission cross section spectra of RB, Rhodamine 6G, and 4-Dicyanmethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) in poly(methyl methacrylate) (PMMA) bulk were determined. The cross section data enable us to predict gain characteristics of RB, R6G, and DCM-doped GI POFA. The wide spectral coverage in the visible is achievable with the GI POFAs doped with several selected dyes.
A (Pb,La)(Zr,Ti)O3 (PLZT) Polarization-Plane Rotator with a Buried Elec trode Structure for a Mid-Infrared Electro-Optical Shutter
Authors: Taniguchi Yoshiharu , Murakami Kensuke , Kobayashi Hiroshi , Tanaka S hosaku
Published: October 2002

A new design of a (Pb,La)(Zr,Ti)O3 (PLZT) polarization-plane rotator
is proposed and tested. The electrodes, parallel to the light propagation di
rection, are buried from the front to the rear surface of the rotator. Owing
to the uniform distribution of the electric field inside the entire volume of
the rotator, the half-wavelength voltage can be reduced to less than 100 V
in the mid-infrared region. This is much lower than the voltage for a conv
entional rotator with plane electrodes, of the order of 600–800 V. By combin
ing the rotator with two polarizers, a mid-infrared electro-optical shutter,
which is applicable to an infrared absorption-type gas monitor, is fabricated
.
Interface Wall Energy in Exchange-Coupled Magneto-Optical Recording Films
Authors: Hwang Wein-Kuen , Jia-Reuy Liu Jia-Reuy Liu , Han-Ping D. Shieh Han-Ping D. Shieh
Published: October 2002

Exchange-coupled double-layered (ECDL) films were adopted to increase density of magnetically induced super-resolution (MSR) media by using center aperture detection scheme, and to improve sensitivity of switching field simultaneously. A carrier to noise ratio of 40 dB was obtained at 0.5 µ m recording marks produced by a switching field of 75 Oe. Temperature dependence of interface wall energy affects recording/playback characteristics of ECDL MSR disks considerably.
Photocurrent Synergism Observed with Sublimed Films of Zinc Tetraphenylporphyrin
Authors: Yutaka Harima Yutaka Harima , Kazuo Yamashita Kazuo Yamashita
Published: October 2002

Synergism in photocurrent observed with vacuum-sublimed films of zinc tetraphenylporphyrin (ZnTPP) is described in detail. The photocurrent synergism appears when a ZnTPP thin film sandwiched between two dissimilar metals is illuminated simultaneously with visible (VIS) and near-infrared (NIR) light. The magnitude of the synergism (η) at a fixed VIS light depends on the wavelength of the NIR light, which is not appreciably absorbed by the ZnTPP film, whereas the response of η to varying wavelengths of VIS light at a fixed NIR light exhibits a peak at 430 nm, where the ZnTPP film absorbs light most intensively. In addition to these η spectrum measurements, dependences of η on the intensities of the 430 nm and NIR light, film thickness, and bias voltage are examined for clarification of the mechanism of the synergistic effect.
Structural Behavior of Thin BaTiO3 Film Grown at Different Conditions by Pulsed Laser Deposition
Authors: Zhang Jie , Cui Dafu , Lu Huibin , Chen Zhenghao , Zhou Yueliang , Li Lin , Yang Guozhen , Martin Szabadi , Hess Peter
Published: October 2002

Thin epitaxial BaTiO3 (BTO) films having a high crystallinity and uniformity of grains were deposited on the SrTiO3 (STO) substrates. When the oxygen pressure is from 0.04 to 70 Pa the lattice constant decreases from 4.1100 to 3.9972 Å and the orientation normal to the substrate changes from (001) to (100). The surface topography changes from flat to hilly with a surface roughness (rms) changing between 1.2 nm at 0.7 Pa, 3.4 nm at 7 Pa and 6.4 nm at 70 Pa. At the substrate temperature of 550, 750 and 850°C the surface topography of the films varies from corrugated structure to rectangular grain and the surface roughness increases from 1.2, 3.4 to 3.4 nm. The epitaxial BTO films were also deposited on the YBCO/LaAlO3 (YBCO/LAO) substrates at 750°C and 7 Pa. The films have a rough surface (rms=29.1 nm), but a good uniformity of grains. The c-axis oriented BTO films with a poor crystallinity were deposited on the MgO substrates at 750°C and 7 Pa. The films have a smooth surface (rms=1.0 nm), but a poor uniformity of grains. The interfaces between the BTO films and the substrates were determined by transmission electron microscopy (TEM).
Ultrasonic Velocity and Absorption in (V2O5)x(GeO2)y(P2O5)1-x-y Glasses
Authors: Maiti A. , Mukherjee S. , U. S. Ghosh U. S. Ghosh , C. Basu C. Basu
Published: October 2002

The velocity and attenuation of longitudinal and transverse ultrasonic waves in four different compositions of (V2O5)

x

(GeO2)

y

(P2O5)1-
x
-
y

glass system with P2O5 concentration ranging from 2.85 to 15.44 mol% have been measured at temperatures between 80 and 300 K using the ultrasonic pulse echo technique at 8 MHz. The results indicate that for low concentration of GeO2 (y<0.5) the velocities decrease slowly and monotonically throughout the entire range of temperature but for higher concentration (y>0.5) velocity variation shows a minimum. The attenuation shows broad high temperature relaxation peak for all samples.
Development of CH4-Radio-Frequency-Plasma-Enhanced Chemical Vapor Deposition Method with a Positively Self-Biased Electrode for Diamond-Like Carbon Film
Authors: Inaba Hiroshi , Kokaku Yuuichi , Terakado Masatomo , Kataoka Hiroyuki
Published: October 2002

We developed a radio-frequency-plasma-enhanced chemical vapor deposition (CVD) method with a positively self-biased electrode system. This method enables simultaneous ion-assisted deposition on both sides of a vertically suspended substrate at a grounded electrical potential with one rf generator. In the positively self-biased electrode system, the cathode sheath is located close to the grounded electrode. Accordingly, positive ions are accelerated toward the grounded electrode, producing an ion-assisted reaction on the surface of the substrate. The grounded substrate is advantageous when transporting a substrate holder suspended vertically in an in-line multilayer deposition system. An important feature of this electrode is the electrical capacitance between the hollow anode chamber and the ground which is parallel to the sheath capacitance. Application of the electrode to the deposition process of thin film magnetic recording disks in pure methane gas was investigated. Diamond-like carbon (DLC) films were deposited at a rate of 3 nm/s on the magnetic layer, with uniform film thickness within ±5% over a substrate measuring 95 mm in diameter. Analysis of this film showed that its characteristics are essentially the same as those of DLC film deposited by the conventional method using a cathode sheath on a high-voltage electrode.
The Effect of Oxygen on the Delay Time of Flashover by a Laser-Produced Plasma
Authors: Masafumi Jinno Masafumi Jinno , Makoto Kubo Makoto Kubo , Masaharu Aono Masaharu Aono , Ryohei Itatani Ryohei Itatani
Published: October 2002

The delay time of discharge triggered by a laser-produced plasma is investigated in a mixture of oxygen and nitrogen. When oxygen exists in the mixture, the delay time of discharge has two styles of “late discharge” and “early discharge”. The delay time of “late discharge” agrees with the transit time of oxygen negative ions between electrodes. The delay time of “early discharge” approaches the transit time of electrons between electrodes as the applied voltage between the electrodes increases. There exists a threshold voltage at which the delay time leaps from “late discharge” to “early discharge”. Calculation of the electron detachment cross section reveals that the leap of the delay time is caused by changing of negative particle triggering discharge from oxygen negative ions to electrons due to an increase in electron detachment as the applied voltage becomes higher.
Two-Dimensional Fluid Simulation of Capacitively Coupled RF Electronegative Plasmas
Authors: Chung Tae Hun , Meng Lin , Lee Hyun Jin Yoon
Published: October 2002

A two-dimensional self-consistent fluid simulation of capacitively coupled rf glow discharges of electronegative plasma with a cylindrically symmetric parallel plate electrode is presented. The model equations include continuity equations, a Poisson equation, and an electron energy balance equation. The two-dimensional distributions of charged particle densities, electric potential, electron temperature, and ionization rate are calculated. The effects of the applied rf voltage, the driver frequency, and the gas pressure on the discharge characteristics are investigated in detail.
An Instrument for Ultrasonic Measurements of Small Specimens
Authors: Hiroaki Kamioka Hiroaki Kamioka
Published: October 2002

An instrument which can be used to measure both sound velocity and attenuation in small specimens (about 5×5×5 mm3) is described. A dual path comparison method based on the ultrasonic pulse transmission method was used in the present work. For this measurement method, an easy-to-handle mercury delay line cell was devised. To test applicability of the instrument, sound velocities were measured at 10 MHz for synthetic silica glasses and a single crystal of sodium chloride along the [100] axis at room temperature. The accuracy of the measurements was better than 0.2%. As a further example, sound velocities and attenuation in the ceramic barium titanate, BaTiO3, were measured in the temperature range from room temperature to 200° C. A large peak was detected in the attenuation near the Curie temperature.
Wide Range pH Fiber Sensor with Congo-Red- and Methyl-Red-Doped Poly (Methyl Methacrylate) Cladding
Authors: Egami Chikara , Suzuki Yoshiki , Sugihara Okihiro , Hisashi Fujimura Hisashi Fujimura , Naomichi Okamoto Naomichi Okamoto
Published: October 2002

We introduce an evanescent-wave-spectroscopic fiber optic pH sensor. This sensor has part of the polymer cladding doped with either congo red (CR), which responds to pH=3 to 5, or methyl red (MR), which responds to pH=5 to 7, as the pH sensor film. In this study we succeeded in expanding the measurable pH range by using two pH sensor probes with the different pH sensitivities. In addition making the pH fiber sensor into a probe structure enabled us to achieve high pH sensitivity and to monitor the pH value easily. Reducing the quantity of doped dye made it possible to use the sensor for objects highly sensitive to pH chemical equilibrium.
New Technique of the X-Ray Efficiency Measurement of a Charge-Coupled Device with a Subpixel Resolution
Authors: Hiroshi Tsunemi Hiroshi Tsunemi , Kumi Yoshita Kumi Yoshita , Shunji Kitamoto Shunji Kitamoto
Published: October 2002

We report the use of a new technique to measure the X-ray detection efficiency of a charge-coupled device (CCD) with subpixel resolution. The new technique makes use of a parallel X-ray beam and metal mesh placed just in front of the CCD. The CCD camera we used is a conventional system using the TC213 (Texas Instrument Japan (TIJ)) whose pixel size is 12 µ m ×12 µ m with one million pixels. The mesh has 4 µm diameter holes spaced at 12 µm intervals. We produced an efficiency map within a typical pixel showing the gate structure in detail: a virtual gate, a clock gate and an antiblooming gate. The gate structure we measured is consistent with the manufacturer's design value. By selecting single pixel events, we detected a pixel boundary. Additional plans for application will also be discussed.
Resist Heating in Cell Projection Electron Beam Direct Writing
Authors: Nakajima Ken , Hirasawa Satomi , Naka Onoda Naka Onoda , Hirosi Nozue Hirosi Nozue
Published: October 2002

Electron beam (EB) direct writing systems have often been used for fabricating sub-half-micron advanced devices because EB direct writing is the most practical method for making the required patterns. Recently, the cell projection (CP) method has become indispensable for increasing the writing throughput in the EB direct writing system. However, it is considered that resist heating may be seriously aggravated below the quarter-micron level when the CP method is used, because the total deposited energy, which is irradiated by one CP EB shot, is almost the same as that irradiated by one variably shaped (VS) EB maximum size shot. Resist heating in the case of the CP method is calculated by a finite element method using the ANSYS (Ver. 5.0A: ANSYS, Inc.) program. In particular, thermal diffusion calculation is mainly carried out under the conditions of 50 kV acceleration voltage and 10 A/cm2 current density for practical application to advanced device fabrication. The calculated results suggest that resist heating in the CP method is mainly caused by the horizontal thermal flux between plural EB shots within the area of one CP shot, by the same mechanism as proximity resist heating under the VS method. Therefore, CP EB writing causes horizontal-mode resist heating. In particular, when a low current density is used, this resist heating mode arises significantly. However, CP writing with high acceleration voltage causes a reduction in the rise of the resist temperature, which causes resist heating. When the EB irradiation time is longer than 1.0 µ s under practical EB writing conditions, the resist temperature increases proportionally to the decrease of writing pattern size in the case of the CP writing with a maximum shot size of 5.0×5.0 µ m. It is also shown that the larger the beam blur of an incident beam, the more serious is the resist heating. When a highly sensitive resist (10 µ C/cm2) is used under these practical conditions, however, resist heating in the CP method is prevented without writing throughput degradation regardless of the CP maximum shot size, because the resist temperature does not rise above the thermal denaturation temperature of standard EB resists. Accordingly, the maximum CP shot size, which affects the writing throughput, is determined by the proximity effect and the Coulomb interaction for fine pattern fabrication.
Dark-Field Contrast of Elements in High-Voltage Electron Microscopy
Authors: D. K. Bhattacharya D. K. Bhattacharya , P. Bhakat P. Bhakat
Published: October 2002

A new and simple expression developed by us has been used for the estimation of contrast of thin amorphous specimens in the tilted-beam mode of dark field (DF) imaging using a conventional transmission electron microscope (CTEM). DF contrasts calculated for thin amorphous films of some representative elements in the electron accelerating voltage range between 0.1 to 3.0 MV have been compared with the corresponding bright field (BF) contrasts. The magnitude of the gain in contrast in the DF mode compared with BF one, observed over a wide range of accelerating voltage (φ), microscope aperture (α) and atomic number (Z) of elements, has been highlighted.
Influence of Temperature Rise and Vibration Level on Electromechanical Properties of High-Power Piezoelectric Ceramics
Authors: Tashiro Shinjiro , Masahiko Ikehiro Masahiko Ikehiro , Hideji Igarashi Hideji Igarashi
Published: October 2002

Heat generation phenomena and the change of electromechanical properties of piezoelectric ceramics were measured during high-power vibration using samples with similar electromechanical coupling factors but different mechanical quality factors. The change of the electromechanical properties was separately discussed in terms of the temperature dependence and applied voltage dependence. The vibration velocities during high-power vibration were calculated using these two dependences, and were compared with the measured values. In addition to the electromechanical properties, the jump phenomena of the motional admittance circle around the resonant frequency were investigated using constant-voltage and constant-current driving methods.