bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Oxidation Behavior of TiN Film Caused by Depositing SrTiO 3 Film
Authors: Yanagisawa Yoshio Abe , Katsutaka Sasaki Katsutaka Sasaki
Published: October 2002

TiN thin films are prepared by rf magnetron sputtering in order to examine their applicability as bottom electrodes of dynamic random access memory (DRAM) capacitors. On the TiN thin films, SrTiO3 thin films are deposited in various O2/(Ar+O2) sputtering gas flow ratios and substrate temperatures, and the amount of TiN which is converted to oxide during SrTiO3 deposition is evaluated from the change in its resistance. Thickness of the oxidized TiN was reduced from 43 nm to 7 nm by decreasing the O2 flow ratio from 100% to 0% and decreasing the substrate temperature from 400°C to 300°C during SrTiO3 deposition. The applicability of the TiN thin film as a bottom electrode of DRAM capacitors is discussed.
New Inductive rf Discharge Using an Internal Metal Antenna
Authors: Keiji Nakamura Keiji Nakamura , Yukiyasu Kuwashita Yukiyasu Kuwashita , Hideo Sugai Hideo Sugai
Published: October 2002

In conventional ICP (or TCP) reactors, a rf power is inductively coupled to an antenna placed outside a plasma vessel. Such an external coupling system is known to have several disadvantages. In order to avoid these disadvantages, a new internal coupling system has been developed in which a bare metal antenna is directly immersed in a plasma, thus forming a full metal reactor. This is accomplished by generating magnetic field lines around an antenna conductor, which effectively suppress the electron loss at the antenna and hence suppress the anomalous rise of plasma potential. Magnetic fields near the antenna are formed by superposing a dc current on a rf current along the antenna. This type of ICP enables rf discharges at rather low pressures such as ∼3×10-4 Torr due to the magnetron effect. Other characteristics of internal metal antennas are also discussed.
Crystal Field Effects on Thermal and Magnetic Properties of Er3Co
Authors: Saito Akiko Takahashi , Tutai Akihiko , Sahashi Masashi , Hashimoto Takasu
Published: October 2002

The specific heat and magnetic susceptibility have been measured for Er3Co. The magnetic susceptibility obeys the Curie-Weiss law in the temperature range of 100-300 K with the effective moment µeff=9.52µB. A large magnetic specific heat above the Curie temperature of 13 K was found, which is interpreted in terms of the point-charge model. It is revealed that the crystal field and exchange field are of the same order of magnitude and that the electronic thermal excitations contribute to the magnetic specific heat, resulting in a broad Schottky-type contribution. Moreover, magnetocrystalline anisotropy gives rise to the noncollinear spin structure.
Wide-Viewing-Angle Display Mode Using Bend-Alignment Liquid Crystal Cell
Authors: Miyashita Tetsuya , Yamaguchi Yoshimi , Tatsuo Uchida Tatsuo Uchida
Published: October 2002

To solve the problem of the narrow viewing angle in twisted-nematic-mode active-matrix liquid-crystal display (LCD), we proposed a new LCD mode using a bend-alignment LC cell with an optical compensator. In this new mode, a wide viewing angle with a black state having no viewing-angle dependence was obtained. We discussed the fundamental principle and design rvle of the optical compensator and showed improvement through theoretical and experimental analysis.
Influence of Doped Poly(N-vinylcarbazole) on Poly(3-octylthiophene) Electroluminescence
Authors: Wang Guangming , Yuan Chunwei , Wu Haiming , Yu Wei Yu Wei
Published: October 2002

Organic electroluminescent (EL) cells with one layer of poly(3-octylthiophene) (P3OT) doped with various amounts of poly(N-vinylcarbazole)(PVK)(P3OT/PVK) as the EL-emitting layer sandwiched between indium/tin-oxide (ITO) and aluminium electrodes have been fabricated by spin coating onto ITO.
It was found for the first time that although the resistance of ITO and the work function of the aluminium electrode are high, the (P3OT/PVK) EL cell emits visible red-orange light with the optimum molar ratio of P3OT to PVK at 5 V which corresponds to a current density as low as 30 mA/cm2. However, the luminance and the current density of the P3OT/PVK EL cells at the same bias voltage change with varying molar ratios of P3OT to PVK, indicating that the PVK dopant influences the P3OT electroluminescence. It was proven that an optimum molar ratio must exist among these various molar ratios of P3OT to PVK in the emitting layer.
High-Resolution Electron Energy Loss Spectroscopy on C60 and C70 Epitaxial Films
Authors: Fujikawa Yasunori , Sakurai Masatoshi , Atsushi Koma Atsushi Koma
Published: October 2002

Vibrational spectra of C60 and C70 epitaxial films grown on cleaved surfaces of MoS2 have been measured by high-resolution electron energy loss spectroscopy. In the case of C60, three intense dipole-active peaks were observed, which correspond to IR-active modes of C60 under the specular reflection condition. In the case of C70, on the other hand, seven dipole-active peaks were found under the specular reflection condition only after annealing, which indicates that the flatness of the surface of the C70 film was improved by annealing. The spectra of C60 and C 70 under the off-specular reflection condition, which correspond to the vibrational densities of states of C
60 and C 70 molecules, resemble each other, indicating that the observed vibrational densities of states are characteristic of fullerenes.
Electron Energy Loss Spectroscopy of Amorphous Boron Filaments
Authors: Suzuki Satoru , Tomita Masato , Takayoshi Hayashi Takayoshi Hayashi
Published: October 2002

Electron energy loss spectroscopy has been used to investigate the B- K spectra of individual filaments grown by electron beam irradiation. We also measured the energy loss spectra of β-rhombohedral boron and B4C for reference. High-resolution transmission electron microscope images, micro-electron diffraction patterns, and elemental analysis by energy loss spectra revealed that the filaments consist of amorphous boron. The similarity of B- K near-edge structures between the filaments and the reference forms of boron suggests that the filaments have B12 icosahedra as their basic structural unit, which is consistent with previous structural studies of amorphous boron. The different peak sharpnesses just above the B- K edge may reflect differences in structural complication and/or disorder of B12 icosahedron units.
Superjunction by Wafer Direct Bonding
Authors: Yamaguchi Hitoshi , Fujino Seiji , Hattori Tadashi , Hamakawa Yoshihiro
Published: October 2002

A pn-junction having a very abrupt impurity profile, called a “superjunction” in this study, was realized by wafer direct bonding (WDB) and low-temperature annealing. To eliminate voids during the low-temperature annealing, a wafer with trenches on the surface was used. A superjunction fabricated by WDB and annealed at 600° C for 30 min achieved a transition width of 42 nm from the p+-peak to n+-peak, which was as narrow as about 1/3 of that of a pn-junction fabricated by ion implantation and diffusion. Additionally, the spreading width of the superjunction was 81 nm, which was about 1/2 of that of a conventional pn-junction.
High Quality a-SiGe:H Alloys Prepared by Nanometer Deposition/H2 Plasma Annealing Method
Authors: Xu Jun , Miyazaki Seiichi , Masataka Hirose Masataka Hirose
Published: October 2002

High-quality hydrogenated amorphous SiGe alloys have been prepared by alternating the deposition of a few-nanometer-thick a-SiGe:H layer and hydrogen plasma annealing using a conventional diode-type PECVD system. Both the hydrogen content and optical band gap are decreased with increasing hydrogen plasma annealing time. A high photoconductivity ( 5.2×10-5 S/cm) and a high photosensitivity of 5×104 have been obtained for samples with an optical bandgap of 1.45 eV.
It is also shown that the light-induced photoconductivity degradation is significantly reduced by hydrogen plasma annealing. The photoconductivity remains at about 80% of the initial value after 360 min light illumination at 100 mW/cm2.
On a Possibility of Wavelength-Domain-Multiplication Memory Using Quantum Boxes
Authors: Shunichi Muto Shunichi Muto
Published: October 2002

A new use of quantum boxes for wavelength-domain-multiplication optical memory applications is proposed. Persistent spectral-hole burning mechanism based on photo-creation of electron-hole pairs and their spatial separation by carrier tunneling is described. We discuss the feasibility of its application to optical data storage with emphasis on the memory duration and the multiplexing factor, that is, the possible number of bits stored in a laser-beam spot following the discussion by Moerner and Levenson.
Photoluminescence of Si0.83Ge0.17 Quantum Wells Grown on (100)Si by Low-Pressure Chemical Vapor Deposition
Authors: Fujinaga Kiyohisa , Furuta Tomofumi , Masaaki Tomizawa Masaaki Tomizawa
Published: October 2002

PL measurements at 77 K are shown for Si0.83Ge0.17 QWs grown on (100)Si at 550° C by LPCVD.
The relation between PL peak energies and QW widths shows good agreement with the theoretical one. The peak shift energy of multiple QWs as it relates to the Si barrier thickness is explained by the change in the ground state energy level of the minibands formed. The PL spectra show a very weak intensity for the D1 line, reflecting defects in the QWs, whose defect density was below the TEM observation limit ( <106 cm-2). The QWs have precisely abrupt Si/SiGe interfaces with a λ value of 0.6 nm.
Interface Structures in AlGaAs/GaAs Quantum Wells Grown by Metalorganic Chemical Vapor Deposition (MOCVD)
Authors: Ikuta Kenji , Shinohara Masanori , Naohisa Inoue Naohisa Inoue
Published: October 2002

AlGaAs/GaAs quantum wells (QWs) were grown by metalorganic chemical vapor deposition (MOCVD) with controlled growth modes: step propagation, and mixtures of step propagation and two-dimensional nucleation. Surface structure on the multilayers was characterized by atomic force microscopy. Photoluminescence (PL) spectra from the QWs with such well-controlled and well-characterized interfaces were obtained for the first time, and PL linewidths were explained by the observed surface structures and growth modes.
An In-Line Optical Bandpass Filter with Fiber Gratings and an Optical Circulator and Its Application to Pulse Compression
Authors: Komukai Tetsuro , Miyajima Yoshiaki , Masataka Nakazawa Masataka Nakazawa
Published: October 2002

In-line optical bandpass filters having sharp spectral edges are demonstrated for the first time by combining an optical circulator and fiber gratings. The maximum transmission including the optical circulator is 65%. A spectral windowing technique using the filter enabled a picosecond pulse from a gain-switched DFB LD to be shortened from 35 ps to 28 ps.
Epitaxial Growth of GaN on Sapphire (0001) Substrates by Electron Cyclotron Resonance Molecular Beam Epitaxy
Authors: Cho Sung Hwan , Sakamoto Hirosi , Akimoto Katsuhiro , Okada Yoshitaka , Mitsuo Kawabe Mitsuo Kawabe
Published: October 2002

GaN epilayers were grown on Al2O3(0001) substrate by electron cyclotron resonance molecular beam epitaxy. The effects of growth parameters such as growth temperature, nitrogen pressure, Ga cell temperature and substrate-surface nitridation on crystal quality were investigated by scanning electron microscope and X-ray diffraction. It was found that the formation of Ga droplets at the growth surface depends strongy on growth temperature and Ga cell temperature, and flat and smooth surfaces were obtained at the growth temperature of 750° C with the growth rate of 0.5 µ m/h. The III/V ratio has a large effect on the full width at half maximum (FWHM) of the X-ray diffraction (XRD), i.e., on the relaxation of misfit stress. However, substrate-surface nitridation has little effect on the relaxation of misfit stress.
Microstructure of Low-Resistivity Tin-Doped Indium Oxide Films Deposited at 150∼200°C
Authors: Yi Choong Hoon , Shigesato Yuzo , Yasui Itaru , Takaki Satoru
Published: October 2002

Low-resistivity (∼2×10-4 Ω· cm) tin-doped indium oxide (ITO) films were deposited at a relatively low substrate temperature (T
s) of 185° C by two representative low-temperature processes, i.e., dc magnetron sputtering using an oxide target and activated e-beam evaporation. Precise X-ray diffraction (XRD) measurements for both ITO films showed that all the XRD peaks split into two peaks with different intensity ratios depending on the deposition conditions and methods. The deconvolution analyses on the doublet XRD peaks and an investigation of the step-etched ITO films revealed that the films consisted of two differently strained layers. The weakly strained layer was consider to be formed as a result of crystallization of an as-deposited amorphous layer upon thermal annealing during deposition (solid-phase crystallization), whereas the strongly strained layer was an as-deposited crystalline layer (vapor-phase crystallization).
Measurements of Drift Surfaces in Compact Auburn Torsatron
Authors: Morimoto Shigeyuki , Lin Hong , Hartwell Gregory J. , Schneider Todd A. , Knowlton Stephen F. , Gandy Rex F.
Published: October 2002

Electron drift surfaces have been measured using beam mapping method in Compact Auburn Torsatron. The electron beams with the energy 0.1 keV≤E≤2 keV are launched parallel to the toroidal magnetic field ofB=(0.04∼0.05) T. Shift of the drift surface from magnetic surface is measured as a function of beam energy which shows an agreement with a theoretical prediction. Behavior of drift orbits near magnetic islands has been also investigated.
Heterostructure Electroluminescent Diodes Prepared from Self-Assembled Multilayers of Poly(p-phenylene vinylene) and Sulfonated Polyaniline
Authors: Onoda Mitsuyoshi , Yoshino Katsumi
Published: October 2002

Multilayer heterostructure thin films of electroactive polymers such as poly( p-phenylene vinylene) (PPV), -precursor and sulfonated polyaniline (SPAn), have been successfully fabricated by a process based on the spontaneous self-assembly of conjugated polyion on a substrate. We have prepared SPAn/PPV multilayer-heterostructure light-emitting diodes (LEDs) using this electrostatic self-assembly technique and discussed the electroluminescence (EL) properties. The thickness of each bilayer is about 20 Å. The LED device composed of 10 bilayers has a turn-on voltage of about 1.4 V and greenish-yellow light was clearly observed under normal room illumination even at low driving voltage. These results are discussed in terms of radiative recombination of the singlet polaron-excitons formed by injection of electrons and holes and the formation of polaron-excitons in PPV layers of SPAn/PPV heterostructures.
Quantitative Determination of Friction Coefficients by Friction Force Microscopy
Authors: Putman Constant , Igarashi Masaru , Reizo Kaneko Reizo Kaneko
Published: October 2002

A new way of obtaining absolute friction coefficients using the friction force microscope is presented. For microfabricated cantilevers it is very difficult to calculate reliable torsion and normal spring constants; both the shear and the Young's modulus are not well known. Their ratio, however, is constant and close to the bulk value. This fact is used to obtain quantitatively reliable friction coefficients. Furthermore, a new calibration method for the friction-signal detector is introduced. The measured friction coefficients for a silicon-nitride tip on mica, silicon and glass are: 0.071, 0.20 and 0.23. Occasionally non-linear effects, indicating possible single-asperity friction, were observed.
Energy Dependence of the Electron-Capture Cross Section of Gap States in Undoped a-Si:H Films
Authors: Chen Yeong E. , Wang Fang Shing , Tsai Jun Wei , Huang Chung Cheng Huang Chung Cheng
Published: October 2002

Isothermal capacitance transient spectroscopy (ICTS) has been employed to measure the energy dependence of the electron-capture cross section of continuously distributed defect levels in undoped a-Si:H film for the first time, via the proposed novel structure. For undoped a-Si:H films, experimental results show that the electron-capture cross section of defect levels initially decreases exponentially, reaches a minimum, and then increases exponentially with energy depth measured from the mobility edge of the conduction band. This v-shaped distribution of the electron-capture cross section of continuously distributed defect levels in undoped a-Si:H film is different from that in phosphorous-doped a-Si:H film. This means that mechanisms other than multiphonon emission can be dominant in the electron-capture process in the gap states in undoped a-Si:H film.
Absence of Correlation between Disorder and Defect Density in Hydrogenated Amorphous Silicon
Authors: Ganguly Gautam , Sakata Isao , Okushi Hideo , Akihisa Matsuda Akihisa Matsuda
Published: October 2002

We find no correlation between a significant variation of the disorder induced band-tail density-of-states distribution and the density of either annealed or light-induced metastable defects in hydrogenated amorphous silicon, which contradicts some currently prevalent notions about the origin of these defects.
New Data on Electrical Properties and Antiferromagnetism of Highly Oxidized Perovskite SrFeOx ( 2.5<x<3.0)
Authors: Nakamura Shin , Shuichi Iida Shuichi Iida
Published: October 2002

Nearly metallic conduction on the order of 10-3 Ω· cm was observed in the polycrystalline perovskite SrFeO2.92. The temperature coefficient of resistivity dρ/ dT, however, was negative down to 12 K, indicating that the material is not truly metallic. The activation energy for conduction becomes noticeably small in the antiferromagnetically ordered state. The double-exchange approach might be adequate to explain these behaviors. For the oxygen-deficient specimens, thermoremanent magnetization due to parasitic ferromagnetism was observed.
Origin of Second-Harmonic Generation in Vacuum-Evaporated Copper Phthalocyanine Film
Authors: Yamada Toshiki , Hoshi Hajime , Ishikawa Ken , Takezoe Hideo , Atsuo Fukuda Atsuo Fukuda
Published: October 2002

In situ observation of second-harmonic generation (SHG) was made as a function of film thickness of centrosymmetric copper phthalocyanine during the evaporation process. In order to clarify the origin of the relatively strong SHG, the experimental results were compared with calculations based on the electric dipole, electric quadrupole and magnetic dipole mechanisms. The comparison clearly ruled out dipolar origin and strongly indicates electric quadrupolar or, more preferably, magnetic dipolar origin.
Magnetoresistance Properties of Cu/Co/Cu/NiFe Multilayers with a Few Stacking Numbers
Authors: Miyauchi Daisuke , Satoru Araki Satoru Araki
Published: October 2002

[Cu/Co/Cu/NiFe]

N

multilayers were prepared using electron-beam evaporation in an ultrahigh vacuum and their magnetoresistive (MR) properties with a few stacking numbers (N) were studied. The N dependence of the MR property was affected by the magnetic layer thickness. In the range of N≦2, a thick magnetic layer was required to obtain a large MR ratio. In the multilayer of Cr(50 Å)/NiFe(50 Å)/Cu(50 Å)/Co(50 Å)/Cu(50 Å)/NiFe(50 Å) (N=1.5), the MR ratio of 5.6% and the MR slope of 0.5%/Oe were obtained.
Surface Orientation of Polyimide Alignment Layer Studied by Optical Second-Harmonic Generation
Authors: Shirota Koichiro , Ishikawa Ken , Takezoe Hideo , Fukuda Atsuo , Shiibashi Toru
Published: October 2002

We have determined the orientational distribution function (ODF) of the side chains of polyimide films for liquid crystal alignment. To determine ODF, optical second-harmonic generation was measured as a function of sample rotation angle. Using nonlinear susceptibility components obtained by a fitting procedure, ODF was obtained by means of information entropy. The symmetry of the polymer side chains changes from C∞v
to C
s
by rubbing treatment. Asymmetry of the polar angle along the rubbing direction is induced, though the change is very small.
Observation of Compositional Separation in CoCrTa Thin Film Using Transmission Electron Microscope with Imaging Filter
Authors: Kimoto Koji , Yahisa Yotsuo , Hirano Tatsumi , Usami Katsuhisa , Narishige Shinji
Published: October 2002

The elemental mapping of a CoCrTa thin film deposited at 270° C has been performed using a transmission electron microscope equipped with an imaging filter. A compositional separation, which consists of Co-enriched areas and a Cr-enriched phase around them, is quantitatively observed. The Co-enriched areas are about 20 nm in diameter and the Cr-enriched phase extends with a two-dimensional network, which corresponds to grain boundaries. Intragrain Cr-enriched areas, which are less enriched than at the grain boundaries, are also observed.
Rhenium Tips for Scanning Tunneling Microscopy in Air
Authors: Watanabe Miyoko O. , Teruyuki Kinno Teruyuki Kinno
Published: October 2002

The performance of rhenium (Re) tips has been investigated for scanning tunneling microscopy in air. Both tips machined mechanically and tips etched electrochemically from poly-crystalline wires were examined and the tip apexes were observed with a transmission electron microscope. Stable atomic images of graphite surfaces were almost always obtained using the Re tips sharpened mechanically, whose apexes were jagged and had thin oxide layers. Atomic images were not obtained, however, with the electrochemically etched Re tips, whose contamination layers were field-evaporated and the apexes of which were controlled so that a single atom was on the apex of the (112̄0) surface, although atomic images were always observed stably in UHV with these tips.
Hexagonal-Facet Laser with Optical Waveguides Grown by Selective Area Metalorganic Chemical Vapor Deposition
Authors: Ando Seigo , Kobayashi Naoki , Hiroaki Ando Hiroaki Ando
Published: October 2002

A hexagonal facet (HF) GaAs/AlGaAs laser with rectangular optical waveguides is proposed and its preliminary lasing characteristics are presented. The rectangular waveguide is parallel to one side of the HF laser and consists of the same (111)B growth plane and (110) sidewall facets as the HF laser structure. The number of rectangular waveguides extending from one HF laser is changed from one to four to study the effect of the waveguide on lasing characteristics by optical pumping at room temperature. The lasing light can be efficiently taken out from the point of the rectangular waveguides in all laser structures. These lasers keep a ring cavity mode of inscribed hexagon even if the waveguide structures couple with the HF laser structure.
New Epitaxial Growth Method of Cubic GaN on (100) GaAs Using (CH3)3Ga, HCl and NH3
Authors: Miura Yoshiki , Takahashi Naoyuki , Koukitu Akinori , Hisashi Seki Hisashi Seki
Published: October 2002

A new method using (CH3)3Ga, HCl and NH3 sources has been demonstrated for the epilaxial growth of cubic GaN on (100)GaAs substrates. In this method, a GaN buffer layer was deposited on a (100)GaAs substrate at about 500° C prior to the growth of cubic GaN films. The growth rate of cubic GaN was about 3.0 µ m/ h at 850° C. The X-ray diffraction pattern showed only the cubic GaN peak but no hexagonal GaN ones, and the full width at half-maximum (FWHM) of the X-ray diffraction profile of 37.7 minutes was obtained. The room-temperature photoluminescence spectrum of the cubic GaN obtained showed a strong band edge emission at 361.5 nm.
Magnetic Anisotropy of S m2(F e1-x C ox)17Cy
Authors: Izumi Hirokazu , Machida Ken-ichi , Gin-ya Adachi Gin-ya Adachi
Published: October 2002

The magnetic anisotropy of rare-earth iron intermetallic compounds containing cobalt and carbon, Sm2(Fe1-xCox)17Cy(0≤x≤0.5 and 0≤y≤0.5), was investigated.. They crystallized in rhombohedral symmetry of Th2Zn17-type structure, and the easy magnetization direction (EMD) changed from the basal plane to thec-axis of the Th2Zn17-type structure with increase of the contents of Co and carbon, so that the complete uniaxis anisotropy was realized on Sm2(Fe0.7Co0.3)17C0.3. The Curie temperature is elevated by substitution of Co for Fe and interstitial addition of carbon, and the effect of Co was marked compared with that of carbon.
Enhancement Effect of Plasma Enhanced Chemical Vapor Deposited SiN Capping Layer on Dielectric Cap Quantum Well Disordering
Authors: Choi Won Jun , Lee Seok , Zhang Jingming , Kim Yong , Kim Sang Kuk , Lee Jung Il , Kang Kwang Nham , Cho Kyuman
Published: October 2002

Quantum Well disordering of GaAs/AlGaAs multiple quantum well(MQW) has been accomplished with only plasma enhanced chemical vapor deposited (PECVD) SiN cap layer growth. The amount of blue shift increases with SiN growing time. This result has been explained by the vacancy indiffusion during PECVD SiN growth. Rapid thermal annealing (RTA) of the sample after SiN cap layer growth at 850° C for 35 s caused a larger amount of blue shift than those obtained without RTA.
By considering the model of Al diffusion from AlGaAs barrier into GaAs QWs together with the result from photoluminescence (PL) measurement, Al diffusion coefficients were calculated. The Al diffusion coefficient due to PECVD SiN was estimated at about 3×10-17 cm2/ s. It was possible to extract the effect of RTA on the QW disordering, which showed that the amount of the blue shift and the Al diffusion coefficient due only to RTA increases with SiN cap layer thickness as reported by Chi et al.10)
Transmission Electron Microscopy Study of La-Doped Bi-Sr-Cu-O Compound
Authors: Lu Bin , Li Fang-hua , Chen Hong , Liu Wei , Mao Zhi-qiang , Zhang Yu-heng
Published: October 2002

A La-doped Bi-Sr-Cu-O phase is studied by electron diffraction and high-resolution electron microscopy. The space group of the crystal is Ccca and the lattice parameters are a=5.39 Å, b=23.5 Å, and c=34.0 Å. The structural difference between the present compound and the Bi4Sr8Cu5O

z

phase is discussed. The origin of high temperature superconductivity in this sample is proposed.
Fluorination of Fullerene Film by CF4 Plasma
Authors: Mieno Tetsu , Sakurai Atsushi
Published: October 2002

Fullerene thin film is fluorinated by a cold cathode DC discharge of CF4 gas. From the measurement of a laser-desorption time-of-flight mass spectrometer, it is confirmed that the surface of fullerene film becomes fullerene fluoride such as C60F

x

(x=15-51), and that C60F33 has the largest intensity. It is believed that fluorination is performed by F radicals and F
- ions in the plasma. This fluorination method is safe and is attractive for producing fullerene fluoride film on solid substrates.
Reduction of Deep Level Impurities in Zn-Doped AlxGa1-xAs by a Co-Dopant Technique
Authors: Chen J. C. , Huang Z. C. , Yu Tao , Chen H. K. , Lee K. J.
Published: October 2002

By using a novel co-dopant technique in the metalorganic chemical vapor deposition (MOCVD) process, we have achieved very low deep level densities (Nt<5×1013cm-3) and improved optical properties in Zn-doped (NA-ND=1×1018cm-3) Al0.2Ga0.8As epitaxial layers. This technique employed both p- (Zn) and n-type (Se) dopants in the growth of p-type Al0.2Ga0.8As. Samples were characterized by deep level transient spectroscopy (DLTS) and photoluminescence (PL). We have found that a small amount of Se (n∼8×1016/ cm3) in Zn-doped (p∼1×1018/ cm3) Al0.2Ga0.8As will significantly reduce the density of deep level impurities (by more than one order of magnitude) and increase the photoluminescence efficiency.
Light-induced Annealing of Photocreated Dangling Bonds in Hydrogenated Amorphous Silicon
Authors: Nishino Qing Zhang , Minoru Kumeda Minoru Kumeda , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

Light-induced annealing (LIA) of photocreated dangling bonds in hydrogenated amorphous silicon has been well comfirmed, but the mechanism for the LIA is still disputed. In order to distinguish the LIA from thermal annealing, we investigate the effect of the LIA on the distribution of thermal annealing activation energies for photocreated dangling bonds. We find that the LIA mainly annihilates the photocreated dangling bonds with a smaller thermal annealing activation energy. Taking this result into account, we discuss the models proposed for the LIA.
Localized-State Distributions in Ag-Modified As2Se3Glasses
Authors: Mikitaka Itoh Mikitaka Itoh , Keiji Tanaka Keiji Tanaka , Michihiko Kitao Michihiko Kitao
Published: October 2002

Localized-state distributions in Agx(As0.4Se0.6)100-xglasses, where 0 ≤x≤ 35, have been investigated using the transient photoconductivity technique. In all the glasses, the density of tail states above the valence band appears to be distributed exponentially, ∝exp (-E/kT0), whereT0is the characteristic temperature. With an increase inx,T0increases, but atx≥ 10, it decreases. This composition dependence can be accounted for by assuming the formation of Ag–Se bonding states above the nonbonding Se valence band.
Etching of AlxGa1-xAs (0≤x≤1) by Trisdimethylaminoarsine
Authors: Goto Shigeo , Nomura Yasuhiko , Morishita Yoshitaka
Published: October 2002

The etching of Al

x

Ga1-
x

As by trisdimethylaminoarsine (TDMAAs) in an ultra-high-vacuum chamber of molecular-beam epitaxy (MBE) was investigated in relation to the Al composition (x) dependence. The etching rate (R
e) of Al

x

Ga1-
x

As rapidly decreased along with an increase in x, reaching almost zero at x=1. At a substrate temperature of 600° C, where the R
e for GaAs was 0.33 monolayer(ML)/s, the R
e of Al

x

Ga1-
x

As with x above 0.06 was one order of magnitude smaller than that for GaAs. In situ Auger electron spectroscopy revealed that the surfaces of AlGaAs exposed to TDMAAs changed to Al-rich surfaces, showing that the Al-rich layer formed as a result of the selective desorption of Ga atoms from the AlGaAs surface terminated the progression of etching.
Fermi Level Pinning in Metal-Insulator-Diamond Structures
Authors: Yuzuru Otsuka Yuzuru Otsuka , Sei Suzuki Sei Suzuki , Shozo Shikama Shozo Shikama , Tetsuro Maki Tetsuro Maki , Takeshi Kobayashi Takeshi Kobayashi
Published: October 2002

Capacitance-voltage (\cv) and electron-beam-induced current (EBIC) measurements were performed on metal-insulator-semiconductive (MIS) diamond structures. Utilizing \bto (BTO) as the gate insulator of diamond MIS structures, experimental results indicate pinning of the Fermi energy at ∼1.7 eV above the valence band edge, which is in excellent agreement with the 1/3 band-gap rule of Mead and Spitzer. This is due to the existence of surface states on diamond presumably induced by oxygen adsorption. Employing \caf in place of BTO reduced the Fermi level pinning to a large extent by virtue of its oxygen-free process.
Ultralow Laser Threshold Operation of InGaAs-GaAs-InGaP Strained Quantum Well Fabry-Perot and Distributed Feedback Lasers
Authors: Sin Y. K. , Horikawa H.
Published: October 2002

Data are presented on ultralow threshold current characteristics of InGaAs-GaAs-InGaP buried heterostructure (BH) strained quantum well (QW) lasers suitable for optical interconnects. As-cleaved 350 µ m-long Fabry-Perot BH strained QW lasers show an extremely low CW threshold current of 0.6 mA and a high slope efficiency of 0.45 mW/mA per facet. Also, uncoated InGaP distributed feedback (DFB) BH strained QW lasers show an ultralow CW threshold current of 2.2 mA and a sidemode suppression ratio (SMSR) of 30 dB.
To the best of our knowledge, this is the lowest threshold current ever obtained from GaAs or InP based DFB lasers.
Epitaxial Growth of Mo Single Crystal on Sapphire by H2 Reduction of MoO3 and Characterization by Reflection High-Energy Electron Diffraction
Authors: Osamu Igarashi Osamu Igarashi
Published: October 2002

Mo depositions on sapphire ( Al2O3) were effected by H2 reduction of MoO3, and the crystallinity of the films was characterized by reflection high-energy electron diffraction (RHEED). In the case of growth on the (11̄02) Al2O3 substrates, single-crystal epitaxial growth of (001) Mo was realized. On (0001) Al2O3, single-crystal Mo was not obtained; Mo deposited on (0001) Al2O3 was composed of three sets of (110)-oriented crystallites. To obtain Debye-Scherrer ring-free Mo films whose RHEED patterns did not include arcs, growth temperatures of 890 and 920° C were required in growths on (11̄02) and (0001) Al2O3 substrates, respectively.
Elastic Recoil Detection Analysis for Hydrogen near the Surface of Chemical-Vapor-Deposited Diamond
Authors: Hiromasa Yagi Hiromasa Yagi , Kazuo Tanida Kazuo Tanida , Kazuhito Nishimura Kazuhito Nishimura , Akimitsu Hatta Akimitsu Hatta , Toshimichi Ito Toshimichi Ito , Akio Hiraki Akio Hiraki
Published: October 2002

Elastic recoil detection analysis (ERDA) was performed to determine hydrogen concentration profiles near the (100) surfaces of epitaxially grown diamond films. Microwave plasma chemical vapor deposition (CVD) was used for the growth. At the end of the growth, the substrates were treated with and without exposure to H2/O2 plasma. The areal density of hydrogen determined by ERDA ranged from 5 to 7 ×1015 atoms/cm2 near the surface of the specimens. These areal densities were 3–4 times larger than that of C atoms on ideal (100) surface of diamond (∼1.6 ×1015).
Disappearance of Yb+ in Excited States from rf Trap by Background Gases
Authors: Sugiyama Kazuhiko , Jun Yoda Jun Yoda
Published: October 2002

Yb+ ions confined in a rf trap disappear due to some background gases when the Yb+ ions are in excited states. We examined O2, H2O, and H2 as the test background gas. We found that O2 gas enhanced the disappearance to a large degree, as did H2O gas to some degree, but H2 gas had little effect.
Iron Concentrations in GaAs Diffused from a Spin-on Film
Authors: Ohsawa Jun , Nakamura Motohisa , Nekado Yoshinobu , Migitaka Masatoshi , Nuio Tsuchida Nuio Tsuchida
Published: October 2002

Secondary ion mass spectroscopy (SIMS) has revealed that spin-on-film diffusion can produce very flat profiles of iron in GaAs, and the concentrations in the range of 1015-1017cm-3are consistent with the solubility of iron at the diffusion temperatures of 650-900° C. The iron accumulation region at the surface is markedly reduced in comparison with that in the conventional method. This technique is useful for introduction of a controlled amount of deep acceptor levels of iron into GaAs.
Contactless Measurement of Electron Mobility in Ferroelectric Gate High-Electron-Mobility Transistor Structures
Authors: Ohmi Shun-ichiro , Tokumitsu Eisuke , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

We have evaluated the electron mobility in BaMgF4/AlGaAs/GaAs(100) high-electron-mobility transistor (HEMT) structures using a contactless mobility measurement system. It has been found that the HEMT structure can be prevented from deteriorating when the BaMgF4 layer is properly deposited, and that dependence of the electron mobility on the N-AlGaAs layer thickness is explained using a simple parallel conduction theory. It has also been found that the electron mobility in the structures is decreased from 6300 cm2/(V·s) to 3300 c
m
2/(V·s) at room temperature as the r
m
B
a
M
g
F
4 growth temperature is increased from 550° C to 650° C.
Transient Characteristics of Luminescence from Barrier-Doped ZnSe:Te-(CdSe)m(ZnSe)nShort-Period Superlattice Quantum Well*
Authors: Chen Boliang , Peng Zhongling , Yuan Shixin , Miyoshi Tadaki
Published: October 2002

Time-resolved photoluminescence spectra have been studied for ZnSe:Te-(CdSe)m(ZnSe)nshort-period superlattice quantum well (SPSQW) for the first time. Decay of both free quantum-well excitons and self-trapped excitons located at spatially separated Te isoelectronic centers in ZnSe barrier was observed to be quite fast in the first 5 ns and then to slow down with a long lifetime tail of more than 10 ns. The influences of both Te content in the barrier and temperature on the equilibrium between the above free and trapped exciton states are discussed.
Field-Induced Second-Harmonic Generation in Cholesteric Liquid Crystal
Authors: Masanori Ozaki Masanori Ozaki , Katsunori Myojin Katsunori Myojin , Sadahito Uto Sadahito Uto , Hiroshi Moritake Hiroshi Moritake , Katsumi Yoshino Katsumi Yoshino , J. S. Patel J. S. Patel
Published: October 2002

The bulk second harmonic generation (SHG) in the cholesteric liquid crystal has been studied. The electric field E induces SHG in cholesteric liquid crystal with small dielectric anisotropy and SHG intensity is proportional to E
2. This electric field dependence is tentatively interpreted in terms of the increase in polarization density due to flexoelectric deformation.
Improvement in Visible Luminescence Properties of Anodized Porous Silicon by Indium Plating
Authors: Ito Toshimichi , Yoneda Toshiyuki , Furuta Keisuke , Hatta Akimitsu , Akio Hiraki Akio Hiraki
Published: October 2002

Luminescence properties of anodically produced porous silicon (PS) have been improved significantly by depositing In metal into micropores. Thin ( ∼300 nm) PS specimens were electrochemically plated in an indium sulfate solution. Observed room-temperature photoluminescence (PL) is very strong in intensity and narrow in spectral width ( ≥0.22 eV). Furthermore, the photodarkening phenomenon, one of the problems of anodized PS, can be reduced for the In-plated PS, compared with as-anodized PS, while room-temperature PL decay times ( ∼10-5 s) are slightly longer for the plated PS than those for as-anodized PS and anodically oxidized PS.
Possible reasons for the observed improvements are discussed.
Laser-Diode-Quality InP/Si Grown by Hydride Vapor Phase Epitaxy
Authors: Tachikawa Masami , Yamada Takeshi , Sasaki Tohru , Mori Hidefumi , Yoshiaki Kadota Yoshiaki Kadota
Published: October 2002

The heteroepitaxial growth of InP/GaAs/Si by hydride vapor phase epitaxy achieves laser diode (LD) device quality. Etch-pit density (EPD) measurements and transmission electron microscopy reveal two kinds of defects, threading dislocations and stacking faults, in the InP layer. Lowering the growth temperature of the direct InP layer on GaAs/Si reduces stacking fault density to the order of 104 cm-2. Room-temperature continuous-wave operation of an InGaAsP 1.5-µ m-wavelength LD fabricated on InP/GaAs/Si confirms its crystal quality.
Kinetics of Crystallization of Amorphous and Mixed-Phase Silicon Films Deposited by Pyrolysis of Disilane Gas at Very Low Pressure
Authors: Kretz Thierry , Pribat Didier , Legagneux Pierre , Plais François , Huet Odile , Renato Bisaro Renato Bisaro
Published: October 2002

The kinetics of crystallization of high-purity amorphous and mixed-phase silicon films obtained by pyrolysis of disilane gas in the millitorr pressure range were studied. A combination of in situ electrical conductance measurements and transmission electron microscopy analysis was used to determine the crystallization parameters. For mixed-phase films we report an activation energy for the nucleation rate of the order of 2.9 eV, compared to approximately 3.7 eV for the completely amorphous ones; the activation energy for the growth rate is roughly equal to 2.7 eV for the two types of films analyzed.
Current-Dependent Kinetic Inductance of Superconducting YBaCuO Thin Films
Authors: Enpuku Keiji , Moritaka Hideki , Inokuchi Hiroyuki , Kisu Takanobu , Takeo Masakatsu
Published: October 2002

Current-dependent kinetic inductance of superconducting thin films is studied experimentally. A measurement circuit for the precise measurement of the kinetic inductance is developed for this purpose. The voltage across an inductance made of YBaCuO meander line is measured as a function of applied current. From the nonlinear relationship between the voltage and the current measured in the experiment, dependence of the kinetic inductance on the current is obtained. The experimental results are consistent with the theoretical results predicted from the Ginzburg-Landau (GL) theory.
High-Luminance Green-Emitting Thin-Film Electroluminescent Devices Using ZnGa2O4:Mn Phosphor
Authors: Minami Tadatsugu , Maeno Takanori , Kuroi Yoshihiro , Shinzo Takata Shinzo Takata
Published: October 2002

A high-luminance green-emitting electroluminescent (EL) device fabricated using a manganese-activated zinc gallate ( ZnGa2O4:Mn) thin-film phosphor in conjunction with a thick barium titanate ceramic insulator has been demonstrated. The green emission was observed in EL devices fabricated using as-deposited ZnGa2O4:Mn thin films prepared by rf magnetron sputtering. A higher luminance was attained for EL devices fabricated using ZnGa2O4:Mn thin films postannealed at 1020° C in an argon atmosphere. A luminance of 710 cd/m2 and a maximum luminous efficiency of 1 lm/W were obtained for a ZnGa2O4:Mn thin-film EL device driven by a sinusoidal voltage at 1 kHz. The device when driven at 60 Hz exhibited a luminance of 230 cd/m2.
Molecular Orientation and Periodical Structure of Vacuum-Deposited Films of Long-Chain Molecules
Authors: Shimizu Hiroshi , Tanigaki Nobutaka , Kazuo Nakayama Kazuo Nakayama
Published: October 2002

The molecular orientation and periodical structure of vacuum-deposited films of n-alkanes and low-molecular-weight polyethylenes were investigated using the wide-angle X-ray diffraction (WAXD) method. The gel permeation chromatography (GPC) measurement indicated that chain shortening occurred in the vacuum-deposited film of polyethylenes with molecular weight higher than 700. From the comparison of WAXD data with GPC data, it was found that the extended chain, rather than the folded chain, is dominant in normal-oriented polyethylene films, though the chain shortening takes place during the vapor deposition process.
Isopropanol Effects on the Phase Formation and Texturing of Sol-Gel Derived PMN Thin Films
Authors: Lee Joon Sung , Kim Chang Jung , Yoon Dae Sung , Choi Chaun Gi , Woo Soung Su , Kwangsoo No Kwangsoo No
Published: October 2002

The effects of isopropanol as a dilute solution were studied on the phase formation, the microstructure and the texturing of sol-gel derived PMN thin films. The films fabricated using only methoxyethanol as a solvent consisted of pyrochlore phase and randomly oriented large perovskite grains. The films fabricated using the solution of 50% methoxyethanol and 50% isopropanol showed relatively lower phase formation temperature and consisted of mainly (111) preferred oriented small perovskite grains. Lead loss at the reaction temperature could be prevented by using the isopropanol as a dilute solution.
Fabrication of Rectangular Holes along 2×4 Unit Cells on GaAs(001) Reconstructed Surface with a Scanning Tunneling Microscope
Authors: Sugiyama Hiroki , Shinohara Masanori , Tanimoto Masafumi , Naohisa Inoue Naohisa Inoue
Published: October 2002

The modification of GaAs (001)-(2×4) reconstructed surface with a scanning tunneling microscope is studied. By applying a high bias voltage pulse between the sample and tip, surface atoms can be extracted and nanometer-scale rectangular “holes” can be made. The sides of the rectangles are along the [110] and the [11̄0] directions, reflecting a surface reconstructed structure. It is considered that isolated As dimers in (2×4) unit cells and unit cells with empty adjacent unit cells are energetically unstable. The reconstructed surface will be useful in the fabrication of nanometer-scale patterns.
Flux Noise from a Metal Surrounding a Superconducting Wire Applied to a Gradiometer
Authors: Takada Youichi , Ueda Masayuki , Kado Hisashi
Published: October 2002

We measure the flux noise generated from a metal covering a superconducting wire. The flux noise from a twisted pair of wires wound with niobium-titanium alloy wire wrapped with copper (Nb-Ti/Cu) is both measured and calculated for various wire lengths. Flux noise is confirmed to be related to the wire length. The flux noise from a first-order gradiometer wound with Nb-Ti/Cu wire is also measured and calculated. The flux noise from this gradiometer, formed with a radius of 7 mm, a base line of 50 mm, and length of 60 mm for a twisted pair of wires, is calculated to be 4.33 µΦ0/ Hz1/2which is in good agreement with the measured result.
X-Ray Photoemission Study of Pr Valence in PrBa2Cu3O7
Authors: Ishii Hiroyoshi , Jokura Kiyoshi , Kataura Hiromichi , Takaaki Hanyu Takaaki Hanyu
Published: October 2002

We have measured the Pr 3d, Cu 2p and O 1s photoemission spectra of PrBa2Cu3O7, YBa2Cu3O7 and related Pr oxides. In the Pr 3d photoemission spectrum of PrBa2Cu3O7, the structure due to the 3d
94f
1 final state (a Pr4+ state) is observed. From the intensity of this structure, the number of Pr 4f electrons is estimated to be about 1.9.
Influence of the Emission Site on the Running Durability of Organic Electroluminescent Devices
Authors: Hamada Yuji , Sano Takeshi , Shibata Kenichi , Kazuhiko Kuroki Kazuhiko Kuroki
Published: October 2002

The influence of the emission site on the running durability of organic electroluminescent devices was examined. The fundamental device structure of MgIn/BeBq2/TPD/MTDATA/ITO ( BeBq2=bis(10-hydroxybenzo[h]quinolinato)beryllium, TPD=N,N′-diphenyl-N,N′-(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine, MTDATA=4,4′,4′′-tris(3-methylphenylphenylamino)triphenylamine) was employed. BeBq2 has the electron transport property, and TPD and MTDATA have the hole transport property. The emitting material [rubrene] was doped in the TPD layer of device A and in the BeBq2 layer of device B. Both devices A and B showed high luminance of more than 10000 cd/m2. However, the running lifetimes of devices A and B, in which the initial luminance of 500 cd/m2 was reduced to one-half under a constant driving current, were 3554 h and 110 h, respectively. It was thus found that the emission site exerts an influence on the running durability.
Deep-Level Transient Spectroscopy of Nitrogen-Doped ZnSe Grown by Metalorganic Vapor Phase Epitaxy
Authors: Goto Hideo , Tanoi Tsutomu , Takemura Masaaki , Toshiyuki Ido Toshiyuki Ido
Published: October 2002

N-doped ZnSe, which was grown on (001)GaAs substrate by metalorganic vapor phase epitaxy (MOVPE) using NH3, was characterized by deep-level transient spectroscopy (DLTS) and photoluminescence (PL). We observed three major deep hole traps of which the energy levels are 640±30 meV, 490±30 meV, 400±20 meV. The density of these traps depends on NH3 supply rate or the ratio of the molar supply rate of Se to Zn.
Response of Chemomechanical Deformation in Polyaniline Film on Variety of Anions
Authors: Keiichi Kaneto Keiichi Kaneto , Masamitsu Kaneko Masamitsu Kaneko , Wataru Takashima Wataru Takashima
Published: October 2002

Dependences of chemomechanical response of polyaniline film on various acids such as aqueous HCl, H2SO4, HClO4 and HBF4 have been studied. Reversible deformation of the film upon oxidation and reduction was directly measured by a laser displacement meter. The deformation ratio of more than 3% was obtained along the stretched direction of the film in HClO4 and HBF4 solution. It is found that the magnitude and transient response of deformation closely relate to the mass of anions.
Charged State Control for Organic Domain Structure by Atomic Force Microscope
Authors: Gemma Nobuhiro , Hieda Hiroyuki , Tanaka Kuniyoshi , Syun Egusa Syun Egusa
Published: October 2002

Nanometer-scale domain structures of organic molecules were fabricated on the SiO2 substrates. The electric charges were injected into the single domain by the contact electrification process using a tip of Atomic Force Microscope. We observed the charge distribution by mapping the surface potential two-dimensionally, and found that the injected charges were stably stored in the isolated domain. The number of injected charges depended on the tip bias during contact, and we succeeded in injecting and imaging only a few elementary charges.
Fabrication and Emission Characteristics of Polycrystalline Silicon Field Emitters
Authors: Hashiguchi Gen , Mimura Hidenori , Fujita Hiroyuki
Published: October 2002

A fabrication method and emission characteristics of polycrystalline silicon (poly-Si) gated field emitters have been presented. The fabrication combines mold emitter fabrication and anodic bonding techniques to transfer the emitters to a Pyrex glass substrate. The tantalum gated structures were fabricated by an etch-back technique using a photoresist process, and a gate opening of about 0.7 µ m has been successfully obtained. The emission characteristics of the fabricated poly-Si field emitters were also presented, showing high current drivability.