bluuebunny/crossref_metadata_2025 huggingface dataset:
Existence of enhanced solid state diffusion during mechanical alloying of Si and Ge
Authors: Schilz J. , Pixius K. , Wunderlich W. , Kaysser W. A.
Published: July 2002

Silicon-germanium was mechanically alloyed in a high energy planetary ball mill and the microstructural development of the solid solution investigated. X-ray diffraction and transmission electron microscopy revealed that alloy formation is accomplished by a solid state diffusion process which is enhanced by the creation of defects and strain during the milling process.
Zn and Te desorption from the (100) ZnTe surface
Authors: Tatarenko S. , Daudin B. , Brun-Le Cunff D.
Published: July 2002

The Zn and Te desorption times from the (100) ZnTe surface have been studied as a function of temperature using reflection high-energy electron diffraction. For Zn desorption an activation energy of 1.8±0.1 eV is found. For Te, due to the existence of different bound states related to different surface reconstructions, c(2×2) and (2×1), activation energies of 1.7±0.1 and 2.50±0.05 eV have been measured.
Intensity noise and facet correlation in Fabry–Pérot laser diodes with low facet reflectivities
Authors: Goobar E. F. , Ram R. J. , Nagarajan R. , Coldren L. A. , Bowers J. E.
Published: July 2002

The intensity noise in Fabry–Pérot lasers with low facet reflectivities is studied. A direct comparison between laser intensity fluctuations under noise suppressed and shot-noise limited current injection is made. Noise levels in excess of the shot-noise level are observed, even when the pump noise is suppressed. Also, an injection current dependent negative correlation between the intensity noise at the output facets of a laser is demonstrated.
Single frequency erbium fiber external cavity semiconductor laser
Authors: Loh W. H. , Laming R. I. , Zervas M. N. , Farries M. C. , Koren U.
Published: July 2002

A novel external cavity configuration for stable single frequency operation of the semiconductor laser is demonstrated. By using an erbium doped fiber as the external cavity, longitudinal mode-hopping is suppressed, ensuring single frequency operation. Employing a 3 m long fiber cavity, resolution-limited optical linewidths of a kHz are obtained.
Model for photoinduced defects and photorefractivity in optical fibers
Authors: Abdulhalim I.
Published: July 2002

A model is proposed for the kinetics of photoinduced defects and the photorefractivity in germanosilicate fibers. It is based on the existence of short lived large energy fluctuations which produce transient traps for carriers that release their energy and enhance defects creation. The enhancement of the photorefractivity with the presence of hydrogen is explained as a result of two mechanisms, that involve the increase in the number of weak bonds and the stabilization of the created defects. In some special cases analytic solutions are found that explain reasonably well the experiments.
Formation of self-aligned holes in an arbitrary pattern in silicon substrate
Authors: Lee Hi-Deok , Lee Ho-Jun , Kim Choong-Ki , Han Chul-Hi
Published: July 2002

A self-aligning etch method for silicon substrates is presented. A hole pattern is defined on the front side of the silicon substrate while etching of the hole takes place from the back side through the application of a current from the front side of the silicon substrate to a cathode electrode in a solution of HF, HNO3, and H2O. As the etching proceeds, the etched pattern in the back side gradually becomes self-aligned with the front side pattern of the silicon substrate. Twenty five circular holes arranged in a 5×5 array are formed in a boron-doped (100) silicon substrate. The etch method provides control over hole dimensions which are 520 μm in diameter and spaced 520 μm apart. The self-aligning property of the etch method enables the formation of different shaped holes.
Observation of the dynamics of electron plasma oscillations in femtosecond laser-produced plasmas
Authors: von der Linde D. , Schüler H.
Published: July 2002

A microplasma is produced on the surface of a glass sample by a 120 fs laser excitation pulse. The optical second harmonic from the plasma is measured using a weak delayed probe pulse. It is shown that the rise and decay of electron plasma oscillations can be mapped out by measuring properly selected second harmonic components as a function of delay time.
Thermally stable amorphous BaxTi2−xOy thin films
Authors: Liu W.-T. , Lakshmikumar S. T. , Knorr D. B. , Rymaszewski E. J. , Lu T.-M. , Bakhru H.
Published: July 2002

The reactive partially ionized beam deposition technique was used to deposit amorphous BaxTi2−xOy thin films with the Ba/Ti ratios from 1 for a stoichiometric BaTiO3 film to 0.2 for a Ti enriched film. A postdeposition annealing between 500 and 600 °C converted stoichiometric amorphous BaTiO3 into polycrystalline structure. This crystallization resulted in densification with a 9% decrease in film thickness. Off-stoichiometric thin films remained amorphous up to 700 °C. Annealed off-stoichiometric BaxTi2−xOy films, however, had lower leakage current and loss tangent than polycrystalline films due to their amorphous nature making them more suitable for electronic applications. At temperatures of 800 °C or higher, significant reaction occurred between the films and Si substrate as detected by Rutherford backscattered spectroscopy.
Injection-level dependent surface recombination velocities at the silicon-plasma silicon nitride interface
Authors: Aberle Armin G. , Lauinger Thomas , Schmidt Jan , Hezel Rudolf
Published: July 2002

Experimental evidence is presented that the effective surface recombination velocity (Seff) at p-silicon surfaces passivated by silicon nitride films (fabricated in a plasma-enhanced chemical vapor deposition system) shows an injection-level dependence similar to the behavior of thermally oxidized silicon surfaces. Using the microwave-detected photoconductance decay method, injection-level dependent Seff measurements were taken on nitride-passivated p-silicon wafers of different resistivities (1.5–3000 Ω cm). The obtained Seff values also show that for low-resistivity substrates (≤2 Ω cm), nitride passivation is as effective as conventional oxide passivation (and even superior at low injection levels) and furthermore offers the advantage of a less pronounced injection-level dependence.
Control of SiH4/O2 chemical vapor deposition using the gas-phase additive C2H4
Authors: Takahashi T. , Egashira Y. , Komiyama H.
Published: July 2002

The effects of adding C2H4 on the chemical vapor deposition (CVD) of SiO2 films from SiH4/O2 were studied at temperatures ranging from 673 to 1073 K using a hot-wall-type tubular reactor. Adding C2H4 improved the step coverage of the films while effectively suppressing the gas-phase formation of particles. Because C2H4 is a well-known radical scavenger, the control of gas-phase chain reactions by consuming atom and/or radical species is responsible for the suppression of particle formation. Comparison of the sticking probability of growth species in SiH4/O2 systems with and without added C2H4 shows that high deposition temperatures are responsible for the improvement in step coverage. The analysis of the carbon content in the films by x-ray photoelectron spectroscopy (XPS) shows no difference in carbon impurity levels between the SiH4/O2/C2H4 and SiH4/O2 chemical systems.
Efficient up-conversion fluorescence in charge transfer compound crystal
Authors: Wang H. Z. , Zheng X. G. , Mao W. D. , Yu Z. X. , Gao Z. L. , Yang G. Q. , Wang P. F. , Wu S. K.
Published: July 2002

A series of new intramolecular charge transfer compounds with absorption bands in shorter wavelengths have been synthesized. Bright visible light emits from the crystals of these new compounds under infrared pulsed laser pumping. The spectral and pump density dependent properties demonstrate that some of the emissions are up-conversion fluorescence due to two photon absorption. The fluorescent yields of one- and two-photon absorption are in the same order at high pump density. This work demonstrates that these new intramolecular charge transfer crystals are good candidates for nonlinear optical materials.
Optical reading and writing on GaAs using an atomic force microscope
Authors: Christenson G. L. , Miller S. A. , Zhu Z. H. , MacDonald N. C. , Lo Y. H.
Published: July 2002

Optically aided reading and writing of gold and tungsten mounds on proton-implanted, multiple quantum well InGaAs/GaAs wafers has been demonstrated using an atomic force microscope (AFM). The system is relatively simple, requiring only a diode laser as the light source, providing a novel, compact, optoelectronic memory system.
Photoreflectance characterization of graded InAlAs/InGaAs heterojunction bipolar transistor layers
Authors: Chen K. L. , Lin H. H. , Jan G. J. , Chen Y. H. , Tseng P. K.
Published: July 2002

The photoreflectance (PR) spectroscopic technique has been used to investigate the microstructures of the graded InAlAs/InGaAs heterojunction bipolar transistor at room temperature. The energy features of the PR spectrum were fitted and identified as band-to-band transitions in the graded layers which were grown using pulsed molecular beam epitaxy and InGaAs as well as InAlAs layers. A linear variation relationship of band gaps with Al composition z was observed and approximated by Eg=0.737+0.759z eV. From the observed Franz-Keldysh oscillations, we have evaluated the built-in dc electric fields in the i-InGaAs collector and n-InAlAs emitter regions. These electric fields are in good agreement with the continuity condition of electric displacements in the interfaces.
Three-wave mixing susceptibility of carrier injected AlGaAs asymmetric quantum wells for mid-infrared difference-frequency generation
Authors: Lee V. W. , Gustafson T. K.
Published: July 2002

We calculate the three-wave mixing susceptibility of an asymmetric AlGaAs quantum well for difference-frequency generation of mid-infrared radiation. The effects of carrier injection and input field strength on the interband mixing process are considered. A peak susceptibility more than two orders of magnitude larger than that of bulk GaAs is obtained. Based on these results, the possibility of difference-frequency mixing within a semiconductor quantum well laser is discussed.
Optical properties of Ti and N implanted soda lime glass
Authors: Was G. S. , Rotberg V. , Platts D. , Bomback J.
Published: July 2002

Soda lime glass was implanted sequentially with Ti+ and N+ to doses ranging from 2 to 30×1016 cm−2 in order to study the resulting optical properties. Analysis of the implant distributions was made by using Rutherford backscattering and x-ray photoelectron spectroscopy and revealed profiles which closely followed each other as designed by the selection of implant energies. Analysis of optical properties showed that the highest dose resulted in an increase in the fraction of infrared reflected by more than a factor of 4 versus 1.7 for the visible regime. The percentage of the total solar radiation rejected exceeded 60% at the highest dose, indicating that the buried layer is highly effective in reducing solar load.
Nonlinear optical response of hydrogenated amorphous silicon films studied by laser induced transient gratings
Authors: Ribeiro R. M. , Margulis W. , Leite C. A. F. , Guedes I. , Misoguti L. , Bagnato V. S.
Published: July 2002

The transient grating technique was used to study the optical properties of hydrogenated amorphous silicon films. A carrier lifetime τe=3.3 μs, a diffusion coefficient D=4.4×10−2 cm2/s, and effective third order nonlinear susceptibility χ(3)=(5.1±1.0)×10−7 esu were measured for λpump=532 nm. The electronic and thermal contributions of the grating were estimated by diffracting a continuous wave HeNe laser beam. For intensities 1.4–4.1 mW/cm2, ∼68% of the response at 633 nm is of electronic origin. A slowly rising diffraction component was also observed.
Multisite nature and efficient lasing at 1041 and 1302 nm in Nd3+ doped potassium yttrium fluoride
Authors: Zhang X. X. , Hong P. , Bass M. , Chai B. H. T.
Published: July 2002

Lasing of Nd3+ ions in different crystallographic sites of KYF4 has been demonstrated to occur at different wavelengths. Low threshold, high efficiency lasing performance at 1041 and 1302 nm were achieved under selective pumping conditions. The stimulated emission cross section at 1041.2 nm was estimated to be 2.6×10−19 cm2 and the radiative lifetime was found to be 600 μs.
Surface topography and step orientation during metalorganic vapor phase epitaxy of InP
Authors: Epler J. E. , Schweizer H. P. , Pedersen J. , Söchtig J.
Published: July 2002

The surface topography during initial and steady state epitaxial growth of InP on InP is monitored with in situ diffuse elastic light scattering. The in situ results are compared with the end-of-run topography measured by ex situ atomic force microscopy. Upon growth initiation, an increase in surface roughness is observed with steps oriented perpendicular to the [011] and [010] direction. After several nanometers of InP deposition, the surface topography planarizes and steady state step-flow epitaxy develops with steps aligned to the pregrowth terrace.
Deposition of boron-nitride films by nitrogen sputtering from a boron-metal target
Authors: Jensen H. , Jensen U. M. , Sorensen G.
Published: July 2002

This contribution deals with reactive growth of boron-nitride films by a rf nitrogen-sputtering process from a boron-metal target; thus nitrogen is functioning both as sputter and reactive gas. Only few and superficial reports of reactive sputter depositions from a metallic boron target in various argon/nitrogen mixtures exist, compared to the number of reports on rf sputtering from a BN target. Nitrogen sputtering of boron-metal has previously not been reported. It was shown by Fourier-transform infrared (FTIR) spectroscopy that the hexagonal structure of BN exclusively was deposited. Sputter rates were measured and showed no dependence on the reactive-gas flow and only a marginal dependence on sputter-gas mixtures containing 20% of krypton, argon, or helium. The reported nitrogen-sputtering process appears to be appropriate for exploration of the key parameters for phase control in BN growth and for additional surface engineering processes such as substrate bias and post-ion bombardment.
SiC power device passivation using porous SiC
Authors: Harris C. I. , Konstantinov A. O. , Hallin C. , Janzén E.
Published: July 2002

A novel technique for the passivation of high power SiC p-n diodes using porous SiC is demonstrated. An increase from around 250 to 600 V in the reverse breakdown voltage is observed following the passivation treatment. The breakdown mode is also reversible in the passivated case in contrast to the permanent degradation in the nontreated device.
Temperature dependence of growth rate of diamond
Authors: Fang P. H.
Published: July 2002

An inadequacy of an Arrhenius type of equation to describe the rate of growth of diamond by a chemical vapor deposition is amended by a Vogel–Fulcher equation. This new equation introduces a critical temperature which predicts an infinite rate of growth as the critical temperature is approached. Some physical mechanisms are suggested.
Deep-level-free AlxGa1−xAs (x=0.22) layer grown by metalorganic chemical vapor deposition
Authors: Huang Z. C. , Yang Bing , Chen H. K. , Chen J. C.
Published: July 2002

We have achieved deep-level-free Al0.22Ga0.78As epitaxial layers using low selenium (Se) doping (8.4×1016 cm−3) grown by metalorganic chemical vapor deposition (MOCVD). Deep levels in various Al0.22Ga0.78As layers grown on GaAs substrates were measured by deep-level transient spectroscopy. We have found that the commonly observed oxygen contamination-related deep levels at EC−0.53 and 0.70 eV and germanium-related level at EC−0.30 eV in MOCVD-grown Al0.22Ga0.78As can be eliminated by Se doping. In addition, a deep hole level located at EV+0.65 eV was found in highly Se-doped Al0.22Ga0.78As epilayers. We suggest that low Se doping (<2×1017 cm−3) produces a passivation effect and then deactivates other deep levels in Al0.22Ga0.78As.
Effect of fluorine co-implantation on MeV erbium implanted silicon
Authors: Liu P. , Zhang J. P. , Wilson R. J. , Curello G. , Rao S. S. , Hemment P. L. F.
Published: July 2002

Fluorine was co-implanted with 2 MeV erbium into silicon substrates. The thermal treatment for implanted samples was started with a 600 °C, 3 h anneal for solid-phase epitaxial regrowth then followed by a 900 °C, 30 min anneal to optically activate the erbium atoms. Photoluminescence measurements have shown a strong enhancement of the luminescence intensity in samples co-implanted with fluorine which, it is suggested, leads to the formation of Er–F complexes and facilitates defect annealing in the silicon lattice. Rutherford backscattering spectrometry was used to characterize the crystalline quality and erbium redistribution after the regrowth.
Si+ implantation: A pretreatment method for diamond nucleation on a Si wafer
Authors: Yang Jie , Su Xiaowei , Chen Qijin , Lin Zhangda
Published: July 2002

Diamond films have been obtained by the hot-filament chemical vapor deposition method on a silicon wafer. The substrates were preimplanted by a Si+ ion beam (ion energy 25 keV, implantation dosage 2×1017 Si/cm2). X-ray diffraction, scanning electron microscopy, and Raman spectroscopy were used to characterize the structure of the synthesized films. The mechanisms for diamond nucleation on a Si wafer have been discussed. Surface stress is believed to be one of the most important factors for low pressure diamond nucleation on the Si wafer.
Preparation of fluorinated gate oxides by liquid phase deposition following rapid thermal oxidation
Authors: Lu Wei-Shin , Hwu Jenn-Gwo
Published: July 2002

The fluorinated gate oxides grown by the method of liquid phase deposition (LPD) following rapid thermal oxidation (RTO) were studied in this work. Samples with and without aluminum are both investigated in the LPD process. It was found that the amount of F atoms decreases as the LPD oxide was treated subsequently by RTO treatment. For a given time of RTO, the longer the LPD time, the larger the amount of F contained in the gate oxides. But for a given time of LPD, the longer the RTO time, the smaller the amount of F contained in the gate oxides. It was found that the radiation induced oxide charge number density shift ΔNot and the midgap interface trap density shift ΔDitm, and the oxide breakdown field Eox exhibit turnaround dependencies on the LPD growth time. In other words, they are dependent on the amount of F atoms incorporated into the gate oxide. Interestingly, it was found that for the gate oxides grown by the LPD process containing Al have better quality than the LPD without containing Al from the viewpoint of radiation hardness and electric breakdown field.
Gas-source molecular beam epitaxy of wide-band-gap Zn1−xHgxSe (x=0–0.14)
Authors: Hara K. , Machimura H. , Usui M. , Munekata H. , Kukimoto H. , Yoshino J.
Published: July 2002

Epitaxial layers of wide-band-gap Zn1−xHgxSe (x=0–0.14) have been grown on GaAs (001) substrates by gas-source molecular beam epitaxy. The epilayers show near-band-edge emission whose emission energy shifts toward lower energies effectively with incorporation of a small amount of Hg. We demonstrate that light emission at a visible spectral region from blue to red can be realized at room temperature with the Zn1−xHgxSe layers by controlling Hg contents between 0 and 0.06.
Plasma synthesis of diamond at low temperature with a pulse modulated magnetoactive discharge
Authors: Ring Zoltan , Mantei Thomas D. , Tlali Spirit , Jackson Howard E.
Published: July 2002

Polycrystalline diamond films have been grown on silicon at substrate temperatures down to 300 °C in a 3 Torr CH4–H2–O2 microwave plasma. The diamond films exhibit characteristic 1333 cm−1 Raman phonon peaks with linewidths of 3–7 cm−1 and a small nondiamond carbon response. Low temperature diamond synthesis was enhanced by applying a static magnetic field to increase gas dissociation and ionization, and by pulse modulating the 2.45 GHz input microwave power to provide a large atomic hydrogen supply without accompanying positive ion bombardment over most of the discharge cycle. Diamond quality is improved and growth rates are at least an order of magnitude higher in the pulsed mode, compared to continuous wave operation with the same average input microwave power.
Enhancement of the flux density of line radiation in the extreme ultraviolet wavelength region for spectroscopic and plasma diagnostic applications using glass-capillary converters
Authors: Kantsyrev V. , Bruch R. , Bailey M. , Shlyaptseva A.
Published: July 2002

New types of focusing optical devices based on glass-capillary converters (GCCs) for the extreme ultraviolet (EUV) region have been constructed and tested. The EUV spectra of He II (np-1s) line radiation have been recorded in the spectral region from 23.0 to 30.6 nm both with and without GCC. Experimentally an enhancement of EUV radiation by a factor of 4–5 has been demonstrated for a small solid angle of the detection system. Theoretically, a computer simulation has been performed producing an enhancement coefficient of about 30–50 for optimal conditions of such experiments.
Ultrahigh precision measurements of optical heterogeneity of high quality fused silica
Authors: De Freitas J. M. , Player M. A.
Published: July 2002

We present ultrahigh precision measurements of the optical heterogeneity of high quality fused silica at the δn=10−8 index level. The measurements were made with a unique scanning heterodyne interferometer developed as part of the Gravity Probe-B Program. Striae of refractive index variation Δn<10−7 (optical path difference smaller than 5 nm) are clearly visible on an extended heterogeneity background of around Δn=6×10−7. Both striae and extended heterogeneities are repeatable to within a few parts in 108. These results show the nature and extent of the heterogeneities of high quality vitreous silica.
High-performance, 2.5-K cryostat incorporating a 100–120-GHz dual polarization receiver
Authors: Archer John W.
Published: July 2002

A hybrid cryostat is described which was designed to cool two SIS mixers in a 100–120-GHz dual polarization receiver. A mechanical refrigerator is used to cool radiation shields surrounding a 4.3-l capacity metal tank containing liquid helium (He4). The temperature of the liquid can be lowered to 2.5 K by reducing the helium vapor pressure in the tank with the aid of a mechanical vacuum pump. A liquid hold time, at 2.5 K, of longer than five days has been achieved. With the mixers cooled to 2.5 K and L-band GaAs FET IF amplifiers cooled to 20 K, single sideband receiver temperatures of less than 120 K have been measured, with >15-dB image rejection and a useful instantaneous bandwidth of 500 MHz.
High-power continuous wave 690 nm AlGaInP laser-diode arrays
Authors: Skidmore J. A. , Emanuel M. A. , Beach R. J. , Benett W. J. , Freitas B. L. , Carlson N. W. , Solarz R. W.
Published: July 2002

High-power diode laser arrays emitting at 690 nm have been developed for solid-state laser pumping. The laser diode bars (fill factor ≊0.7) have been fabricated from single quantum well AlGaInP-based heterostructures. Using silicon microchannel heatsinks, a record high 360 W/cm2 per emitting aperture is achieved under continuous wave operation.
Reduced angular dependence for degenerate four-wave mixing in potassium vapor by including nitrogen buffer gas
Authors: Glassner D. S. , Knize R. J.
Published: July 2002

Degenerate four-wave mixing in alkali vapors exhibits a strong dependence on the angle between the forward pump and probe beams, due to atomic motion. We show that this angular dependence is dramatically decreased by including several hundred Torr of N2 buffer gas in a potassium vapor cell. The angle at which the signal has decreased by half is 250 mrad, an improvement of over 50 times the angle for potassium vapor without buffer gases.
Performance capabilities of reflectometers and ellipsometers for compositional analysis during AlxGa1−xAs epitaxy
Authors: Gilmore W. , Aspnes D. E.
Published: July 2002

Performance capabilities of reflectometers and ellipsometers for determining near-surface dielectric properties by virtual-interface analysis of kinetic data are calculated for the prototypical semiconductor alloy Al0.30Ga0.70As. Measurement of phase as well as amplitude improves relative sensitivities by over an order of magnitude.
Transient current spectroscopy of deep levels in semi-insulating polycrystalline silicon
Authors: Lombardo S. , Campisano S. U.
Published: July 2002

Poole–Frenkel emission by transient current measurements in semi-insulating polycrystalline silicon containing 35 at. % O has been investigated. In the presence of intense electric fields the conductivity of the material is strongly enhanced by the emission of free carriers. By applying square wave voltage signals, the field strength is modulated, thus producing current transients. By the analysis of these transients we have measured the emissivity of the traps responsible for the Poole–Frenkel effect as a function of temperature. The emissivity shows an activated behavior and the corresponding binding energy of the trap results equal to ≊0.64 eV.
Cyclic shifts in the photoluminescence spectra of the porous Si in HF
Authors: Ichinohe T. , Nozaki S. , Ono H. , Morisaki H.
Published: July 2002

Photoluminescence (PL) measurements were carried out on the porous Si layers kept in the HF solution. The PL peak around 700 nm, usually observed in the PL spectrum of the porous Si layer in the air, was no longer detected. This evidence suggests that the origin of the visible light luminescence from the porous Si layer in the air is different from that in the HF solution and may be associated with the presence of oxygen at the surface. Furthermore, it is interesting to find the cyclic shifts in the PL spectra between green and orange by turning the light on and off to illuminate the porous Si layer in the HF solution. This unique behavior is attributed to photochemical etching under illumination and chemical etching of the porous Si layer in the dark.
Femtosecond electron transport in quantum well laser structures with step-graded confinement layers
Authors: Marcinkevičius S. , Olin U. , Wallin J. , Streubel K. , Landgren G.
Published: July 2002

Time-resolved photoluminescence measurements of electron transport are reported in InGaAsP/InP graded-gap separate-confinement quantum well laser structures with a steplike grading profile. It is found that electron transfer over the graded-gap region occurs on a subpicosecond time scale. The upper time limit for the electrons to pass one step of 22 nm width is 250 fs. The fast transfer times imply that the electron transport across the graded region is not affected by the presence of the steps.
Spatial distribution of electric-field domains in n-doped semiconductor superlattices
Authors: Kwok S. H. , Jahn U. , Menniger J. , Grahn H. T. , Ploog K.
Published: July 2002

The spatial arrangement of electric-field domains in heavily doped GaAs-AlAs superlattices was investigated by depth-resolved cathodoluminescence (CL). By measuring the CL spectra for different excitation energies of the electrons, it is shown that the high-field domain is located near the anode. A quantitative analysis of the CL intensities suggests that there is only one domain boundary in the sample.
Simple Nb metal bonding structure
Authors: Chen H. S. , Bacon D. D. , Chen C. H. , Kammlott G. , Jeng G. K. , Werder D. J. , Tai K. L.
Published: July 2002

A simple metallic bonding structure, has been developed consisting of a pure metal Nb and an alloy containing Sn, which can be employed to bond a semiconducting laser device and/or a silicon integrated circuit die to a submount with Au–Sn solder. Differential scanning calorimetry, transmission electron microscopy, and scanning electron microscopy reveal that the Nb layer acts effectively both as an adhesion layer to SiO2 and diamond submounts and as a perfect diffusion barrier against Au–Sn solder. The metallization structure shows no indication of dewetting of the Au–Sn solder. The excellent bonding characters have been attributed to the unique metallurgical properties of Nb.
Passivation of oxidation induced defects in silicon
Authors: Correia A. , Ballutaud D. , Boutry-Forveille A.
Published: July 2002

The effects on minority carrier diffusion length and surface recombination velocity of the oxidation of p-type silicon in a copper contaminated ambient have been analyzed using electron beam induced current. The experiments were carried out on Czochralski and float-zone silicon in order to obtain two different microstructures of defects and copper precipitation modes at the interface, and to study the influence, respectively, on the diffusion length and surface recombination velocity. The diffusion length was drastically decreased in regions free of extended defects, showing the existence of pointlike recombinant defects in the matrix. In each case, it has been evidenced by electron beam induced current measurements and imaging that these pointlike defects were passivated by hydrogen radio-frequency plasma annealing, while no effect was observed on extended recombinant defects.
New phase-change rewritable optical recording film having well suppressed material flow for repeated rewriting
Authors: Hirotsune Akemi , Miyauchi Yasushi , Terao Motoyasu
Published: July 2002

Characteristics of a phase-change optical disk using a (Ge–Sb–Te)-(Cr–Te) recording film containing a high-melting-point component Cr–Te are studied. The high-melting-point component Cr–Te precipitates in the recording film, and prevents a material flow of the recording film during repeated rewrites in which the recording film is melted. There is no drawback such as noise increase by the addition of Cr–Te. Thus the phase-change optical disk using this recording film shows very small distortion in the reproduced signal wave form even after 2×104 rewrites of high-density recording signals that are liable to cause the material flow by forming long and short recording marks on the disk. With a phase-change optical disk, it is easy to overwrite (rewrite without prior erasure) information, which makes it highly suitable for digital recording of motion pictures and sound. They are expected to be used as rewritable compact disks, rewritable CD-ROM disks, rewritable video disks, and small recording media for personal computers.
Spatial subharmonics of moving gratings in photorefractive materials
Authors: Shim Sugie , Kwak Chong Hoon , Lee El-Hang
Published: July 2002

A simple theory based on a nonlinear differential equation derived from Kukhtarev’s materials equations and the coupled mode analysis of wave equation is developed to describe the spatial subharmonics in the photorefractive moving gratings. The optimum detuning frequency of K/2 spatial subharmonic resonance is calculated and compared with experimental data. It is found that our simple theory describes the experimental data very well.
Development of a VUV/soft x-ray monochromator for undulator radiation at the Photon Factory
Authors: Muramatsu Yasuji , Maezawa Hideki
Published: July 2002

A VUV/soft x-ray monochromator was developed for utilizing undulator radiation from a 26-period multipole wiggler/undulator at the Photon Factory. An entrance slitless quasi-Rowland circle mounting was adopted to the monochromator optics, aimed at achieving the compatibility of high resolution with high-output flux. The optics was realized by a decoupling of horizontal focusing with a deflection mirror from vertical focusing with an aberration-free vertical dispersion system which was composed of a cylindrical mirror and a concave grating. The optics and mechanism of the monochromator as well as its test operation made after installation are described.
Magneto-optical and high resolution electron microscopy studies of flux pinning at grain boundaries in Bi2Sr2CaCu2Ox crystals
Authors: Egi T. , Wen J. G. , Kubota H. , Ricketts J. , Koshizuka N.
Published: July 2002

We have studied the flux pinning behavior of Bi2Sr2CaCu2Ox multicrystalline samples using a magneto-optical flux observation method. When a magnetic field is applied parallel to the ab plane, we find low flux density regions at the intersections of small angle grain boundaries. The flux density distribution can be explained by considering both flux pinning at the small angle grain boundaries and the intrinsic pinning effect at the BiO layers. High resolution electron microscopy observations show that amorphous patches with columnar structure exist at the small angle grain boundaries (<20°), while other defects such as misfit dislocations and distorted microstructures appear at general grain boundaries. The fact that flux pinning only occurs at small angle grain boundaries (<20°) indicates that the columnar amorphous structures could act as flux pinning centers.
Ultrafast carrier dynamics in GaSb
Authors: Pelouch Wayne S. , Schlie L. A.
Published: July 2002

The ultrafast carrier dynamics in GaSb are studied using optical transmission-correlation spectroscopy with sub-100-fs pulses. The laser wavelength was tuned between 1.50 and 1.72 μm in order to differentiate between different scattering processes. The carriers scatter out of the initial distribution in 2–2.5 ps with a 200–350 fs component also observed. This faster component, usually attributed to phonon scattering, is observed below the assumed phonon emission threshold. When the laser is tuned above the intervalley scattering threshold a large fraction of the carriers rapidly scatter to the L valley. Saturation of the absorption is measured versus the pump power near the band edge.
Remote photoacoustic measurements in aqueous solutions using an optical fiber
Authors: Russo R. E. , Rojas D. , Robouch P. , Silva R. J.
Published: July 2002

A photoacoustic spectrometer was developed for remote optical absorption measurements in aqueous solutions using an 85-m optical fiber to deliver pulsed tunable dye laser radiation to a sample cuvette located in a glove box. The spectrometer was tested using aqueous solutions of praseodymium ions. Beer’s law was verified down to a concentration of 8×10−6M for an equivalent absorptance of 3.2×10−5 cm−1.
Substrate orientation dependence of low-temperature GaAs grown by molecular beam epitaxy
Authors: Cheng T. M. , Chang C. Y. , Huang J. H.
Published: July 2002

A systematic study of the substrate orientation effect on crystalline quality of GaAs grown by molecular beam epitaxy at low substrate temperature (215 °C) was performed using double-crystal x-ray diffractometer and transmission electron microscopy. The crystal quality was found to be strongly correlated with substrate orientations. Layers of high crystalline perfection with excess arsenic were obtained on both GaAs(100) and (311)B substrates, while columnar polycrystalline growth was observed on (211)B substrate. The transition from a single crystalline state to a polycrystalline state was clearly demonstrated by a 0.5 μm GaAs layer on (111)B surface. Surface kinetic factors are believed to play important roles during the low temperature growth.
High UV (λ≥2200 Å), visible, and near infrared (λ≤0.8 μm) transmissive liquid coolant for high power microwave (2.45 GHz) plasma tubes
Authors: Schlie L. A. , Rathge R. D. , Dunkle E. A.
Published: July 2002

Commercially available dimethyl polysiloxane is shown to be an excellent liquid coolant for the containing walls of high power plasmas (≥300 W/cm3) excited with 2.45-GHz microwaves. This stable, nontoxic, and nonflammable fluid has very low microwave absorption (tan δ=ε″/ε′=3.5×10−4) at this frequency. Fortuitously, it also has excellent ultraviolet, visible, and near infrared (λ≤0.8 μm) transmission. The UV transmission over 1 cm shows 2% transmission at 2000 Å, a 30% transmission at 2200 Å, 80% at 2400 Å, and 100% for λ≳2500 Å. These features plus its good physical (viscosity, thermal conductivity, specific heat capacity, heat of vaporization, and density) and electrical (resistivity and breakdown) properties make it very unique as a liquid coolant of UV emitting microwave plasma lamps. The clear coolant’s infrared absorption for λ≥1.0 μm reduces the radiative (heat) emission from the plasma. In addition, dimethyl polysiloxane has a very wide operating temperature range, −73 °C≤T≤260 °C. Particular procedures required to assure its excellent ultraviolet transmission are described along with different geometrical combinations of liquid cooled plasma lamps and reflector housings. This liquid may also be used to cool microwave excited laser tubes.
TMGa /TEGa interactions in metalorganic molecular beam epitaxy
Authors: Kamp M. , Mörsch G. , Lüth H. , Frese V.
Published: July 2002

Using TMGa and TEGa simultaneously for the metalorganic molecular beam epitaxy growth of GaAs, interactions between the precursors have been observed. Whereas the resulting growth rate is unaffected, the obtained carrier concentrations reveal deviations up to 85% from the superpositioned values. Separate and common injection of both group III alkyls have been investigated. From these, interactions within the common group III injector, if they take place at all, are found to be negligible compared to interactions on the surface.
Phase locking a 3 mm waveband Gunn oscillator with a high T
c superconducting Josephson junction at 77 K
Authors: Wang Huabing , Xu Weiwei , Cheng Qiheng , Ji Zhengming , Gao Ruizhang , Wu Peiheng , Xu Zhicai
Published: July 2002

Using a high-temperature superconducting YBa2Cu3O7−δ Josephson-junction harmonic mixer operated at 77 K and an analog phase-locking loop, we have locked a 3 mm waveband Gunn oscillator to a synthesizer for harmonic numbers ranging from 10 to 52. The spectrum of the phase-locked intermediate frequency reveals good phase-locked quality even for the 48th harmonic mixing between the signal at 104.3 GHz and the local oscillator at about 2 GHz. Our experimental results show that a high Tc superconducting harmonic mixer can work efficiently with high harmonic number for phase locking in the millimeter waveband.
Pulse shaping a high-current relativistic electron beam in vacuum
Authors: Miller J. D. , Nguyen K. T. , Schneider R. F. , Struve K. W. , Weidman D. J.
Published: July 2002

A simple method for shaping the output current pulse of a relativistic electron beam in vacuum is presented. This method has been employed to sharpen the rise time of a high-current relativistic electron beam produced by a 2-MV, 7-kA, 20-ns pulser. The beam has a pulse shape that is approximately triangular both in voltage and current, with a negligible instantaneous energy spread. The desired pulse shape is nominally rectangular in current. The technique utilizes a magnetic lens with a magnitude of approximately 1.5 kG to focus the beam. Passing beam electrons through the magnetic lens causes them to focus at different axial locations downstream from the lens depending upon their energy. The focal point of the beam current peak (corresponding to maximum energy) is then located furthest downstream. An aperture is used near the focus to select a portion of the beam having the desired parameters.
Converting a reflectron time-of-flight mass spectrometer into a tandem instrument
Authors: Haberland Hellmut , Kornmeier Hans , Ludewigt Christoph , Risch Andreas
Published: July 2002

Adding a simple mass gate at the first time focus of a reflectron-type time-of-flight mass spectrometer, one mass can be selected and its further decay or interaction studied. A new type of mass gate is described that does not have any grids. It is especially suitable for cluster studies. Three processes are identified that lead to an undesirable high background in a reflectron time-of-flight mass spectrometer.
Greatly improved adhesion of gold films sputter-deposited on laser-treated and thermally annealed alumina
Authors: Pedraza A. J. , Kumar R. A. , Lowndes Douglas H.
Published: July 2002

The effects on adhesion strength of pulsed-laser irradiation prior to film deposition, and of thermal annealing following film deposition, have been studied for gold films deposited by ion beam sputtering on polished polycrystalline alumina (Al2O3) substrates. Three different atmospheres were employed for the laser irradiations: Ar-4% H2, air, and oxygen, all at 1 atmosphere pressure. A similar functional dependence of adhesion strength on laser energy density, Ed, was found for all of the gaseous environments: No change of adhesion strength for Ed⩽0.5 J/cm2, maximum adhesion for Ed=1.0–1.5 J/cm2, and decreased adhesion for higher Ed. A pronounced increase in gold-alumina adhesion strength was achieved when the alumina substrates were irradiated in an oxygen-rich atmosphere. A post-deposition 300 °C anneal doubled the adhesion strength to ∼50 MPa, approximately 500 times the strength of untreated gold-alumina couples. The adhesion strength initially increased rapidly with annealing time but saturated for times ⩾ 1 hour. The adhesion enhancement can be attributed to the formation of a high-energy disordered alumina surface during rapid solidification following pulsed-laser melting of the near-surface region. This defective surface contains reactive sites where gold atoms can form strong bonds. The data show that these sites most effectively bond gold atoms when they are saturated with oxygen.
Thickness effect on hydrogen plasma treatment on polycrystalline silicon thin films
Authors: Liou Bor Wen , Wu Yi Huang , Lee Chung Len , Lei Tan Fu
Published: July 2002

This letter studies the hydrogen plasma effects on the resistivity, effective free carrier concentration, and mobility of As+- and BF+2-doped polycrystalline silicon (polysilicon) thin films of various thicknesses. It is found that the resistivity increases while the effective free carrier concentration decreases after the plasma treatment as the thickness of the polysilicon film decreases. The mobility typically tends to decrease for the thicker (≳60 nm) polysilicon film, but to increase for the thinner (<60 nm) polysilicon film.
Comment on: ‘‘Modified KTiOPO4 crystals for noncritical phase matching applications’’ [Appl. Phys. Lett. 64, 16 (1994)]
Authors: Phillips Mark L. F. , Harrison William T. A. , Stucky Galen D.
Published: July 2002

The nonlinear optical properties of sodium doped potassium titanate phosphate crystal are discussed. (AIP)
Stability of nitrided silicon dioxide deposited by reactive sputtering
Authors: Jelenkovic Emil V. , Tong K. Y.
Published: July 2002

The electrical properties of nitrided silicon dioxide formed by reactive sputtering in Ar/O2/N2 plasma from the SiO2 target have been studied. The nitrogen mixing ratio was varied from 0% to 15%, with the argon mixing ratio kept at 80%. It is found that as more nitrogen is incorporated, the leakage current increases for electron injection from both aluminum and silicon. By nitrogen reactive sputtering, the interface states generation during constant current stress is greatly reduced in comparison with oxide sputtered in only an Ar/O2 gas mixture. A mixture ratio of Ar/O2/N2 equal to 80:15:5 is found to give optimum oxide quality with good resistance to interface states generation and low leakage current.
Stabilization of a superconducting TbSr2Cu2.85Re0.15O7+δ compound and the valence state of terbium
Authors: Murugesan M. , Selvam P. , Sharon M. , Rao M. S. R. , Gupta L. C. , Pinto R. , Gopinath C. S. , Subramanian S.
Published: July 2002

A single-phase Sr-based Tb-123 phase has been synthesized by chemical stabilization. TbSr2Cu2.85Re0.15O7+δ exhibits superconductivity at Tc,zero=22 K. X-ray diffraction results suggest a relatively small orthorhombicity and neutron diffraction studies indicate an excess oxygen content (≥7.2) in the sample. Tb is present as a trivalent ion in the superconducting phase as derived from x-ray photoelectron spectroscopy.
Minority carrier lifetime improvement by gettering in Si1−xGex
Authors: Losada B. R. , Moehlecke A. , Lagos R. , Luque A.
Published: July 2002

Monocrystalline Si1−xGex alloys may be an interesting material for infrared solar applications and dual band gap systems such as GaAs/Si1−xGex. At present, monocrystalline ingots of Si1−xGex have been grown by the float zone (FZ) technique, but the minority carrier lifetime in the wafers is quite low. Gettering treatment by POCl8 over Si1−xGex samples brings about a substantial improvement of minority carrier lifetime, achieving values similar to FZ-silicon wafers, that is over 200 μs in high resistivity samples if the Ge constant is below 5%.
Investigation of high-field domain formation in tight-binding superlattices by capacitance–voltage measurements
Authors: Han Z. Y. , Yoon S. F. , Radhakrishnan K. , Zhang D. H.
Published: July 2002

A method involving capacitance–voltage (C–V) measurements has been used to investigate the process of high-field domain formation in semiconductor structures with tight-binding GaAs/AlGaAs superlattices grown by molecular beam epitaxy. Current–voltage (I–V) measurements carried out at 77 K showed two series of current oscillations associated with the sequential tunneling process as a result of the high-field domain formation. Accumulation of electrons in the quantum wells due to the extension of the high-field domains through the superlattice as a result of increasing bias is detected as a sharp increase in the capacitance which clearly corresponds to a sharp reduction in the current. Preliminary results of the frequency dependence of the C–V characteristic corresponding to the sequential tunneling process as an effect of the high-field domain formation are discussed.
Thin films of uniform thickness by pulsed laser deposition
Authors: Ianno N. J. , Erington K. B.
Published: July 2002

In order to enhance the utility of pulsed laser deposition, a method to deposit uniform films has been devised. The target and substrate are offset from each other and the substrate is rotated about its axis between laser pulses. We have simulated this process using experimentally determined deposition profiles. Films of uniform thickness to within a few percent across a substrate 5.08 cm in diameter have been fabricated, where we have obtained excellent agreement between theory and experiment.
Electron beam induced conductivity measurements on porous silicon based structures
Authors: Jasutis V. , Šimkienė I. , Krotkus A.
Published: July 2002

Electron beam induced conductivity measurement has been used for investigating the internal electrical field distribution in porous silicon based diode structures. Two carrier collection current peaks were found; one corresponding to the metal-silicon contact region, the second to the interface between the porous and the single-crystalline parts of the structure. It is shown that the latter peak is caused by the built-in electrical field at the contact between silicon and the electrolyte remaining in the pores.
A simple lateral force sensing technique for near-field micropattern generation
Authors: Shchemelinin Anatoly , Rudman Michael , Lieberman Klony , Lewis Aaron
Published: July 2002

We present a simple and general purpose implementation for monitoring the lateral forces between a near-field optical probe and a surface. A feedback system based on this technique has been incorporated into a near-field optical fabrication system based on heatless material removal with an argon fluoride excimer laser. This has allowed the construction of an instrument that is capable of directly patterning a wide variety of materials with a resolution of less than 50 nm.
Nonequilibrium dynamic conductivity of superconductors: An exploitable basis for high-energy resolution x-ray detectors
Authors: Gulian A. M. , Van Vechten D.
Published: July 2002

A new design for high-energy radiation/particle detectors is presented. The nonequilibrium response of a superconductor to the absorption of the incident quanta is sensed by electromagnetic measurements of the altered dynamic conductivity. Microwave absorption may be used to amplify the signal. Such a detector will provide better energy resolution than semiconducting charge-collection devices once the statistical resolution limit is reached.