bluuebunny/crossref_metadata_2025 huggingface dataset:
Semiconductor-ferroelectric nonvolatile memory using anomalous high photovoltages in ferroelectric ceramics
Authors: Brody P. S.
Published: February 2003

A small ferroelectric ceramic element is used with an insulating gate transistor and two diodes as an electrically addressed, nonvolatile memory device which is read out nondestructively. The device uses the anomalous photovoltaic effect in ferroelectric ceramics, an effect in which the polarity and magnitude of photovoltages depend on the direction and magnitude of remanent polarization. Experimental results give memory characteristics. The device could be programmed with pulses as short as 200 ns. There is long-time retention of stored data.
Carbon in molecular beam epitaxial GaAs
Authors: Stringfellow G. B. , Stall R. , Koschel W.
Published: February 2003

The carbon content of GaAs grown by the molecular beam epitaxial technique has been varied by varying the UHV pumping conditions and the growth temperature. The higher carbon content is evidenced by the increased conduction band to carbon acceptor transition observed in the 3.5-K photoluminescence spectrum. The GaAs specimen with highest carbon content is found to have a considerably reduced room-temperature mobility.
Selective observation of electrically active grain boundaries in silicon
Authors: Redfield David
Published: February 2003

A simple technique is described for selective observation of those grain boundaries in polycrystalline Si that would be most harmful to the properties of a solar cell if a cell were to be made from that material. The technique is based on the alteration of the optic axis of liquid crystals by fringing fields at the surface of polycrystalline Si. It is found that the pattern of boundaries seen this way correlates well with the pattern of the most active boundaries as seen in a light-spot scan of a solar cell. This technique has revealed that in p-type Wacker ’’Silso’’ material, the electrical properties of grain boundaries are strongly affected by heat treatment.
Radiation-induced luminescence in silica core optical fibers
Authors: Marrone M. J.
Published: February 2003

The spectrum of the luminescence in silica core optical fibers under x-ray excitation has been observed to consist of two distinct emission bands at 450 and 650 nm. The contrasting dose-dependent behaviors of the two bands show that they are associated with different luminescent centers in the glass matrix. The application of the radiation-induced luminescence in fibers for radiation detection and real-time dosimetry is outlined.
Pulsed Raman measurement of the onset of recrystallization in laser annealing
Authors: Lo H. W. , Compaan A.
Published: February 2003

We have made the first time-resolved measurement of the onset of recrystallization following pulsed laser irradiation of ion-implanted silicon. We find recrystallization to be nearly complete 25 nsec after a 7-nsec annealing pulse with focused energy density of 0.6 J/cm2.
Precisely controlled shallow p+ diffusions in GaAs
Authors: Ghandhi S. K. , Field R. J.
Published: February 2003

Precisely controlled shallow p+ diffusions have been made in GaAs using ZnO/SiO2 as a doped oxide source for zinc, and a layer of phosphosilicate glass as a cap. Diffusions were made in an open-tube system with a nitrogen gas ambient, and exhibit a junction depth reproducibility of better than ±5%. The technique is shown to be relatively insensitive to all process parameters other than diffusion time and temperature, and to be comparable in convenience and ease to diffusion in silicon.
Geminate recombination in a-Si:H
Authors: Mort J. , Troup A. , Morgan M. , Grammatica S. , Knights J. C. , Lujan R.
Published: February 2003

Combined xerographic measurements and a delayed-collection field technique have been applied to a-Si:H. to determine whether geminate recombination controls the photogeneration process in a-Si:H. The delayed-collection field method allows the photogeneration efficiency at low applied fields to be measured. The results show that, depending on sample preparation, the zero-field quantum efficiency ranges from 0.44 to 0.55. The measured field dependence of the quantum efficiency give best fits to the Onsager theory with r0  ∼45 to 80 Å for Φ0=1.
Laser annealing of native oxides on GaAs
Authors: Ahrenkiel R. K. , Anderson G. , Dunlavy D. , Maggiore C. , Hammond R. B. , Stotlar S.
Published: February 2003

Annealing of native oxides grown on GaAs has been performed using a pulsed KrF laser. This process allows the oxides to be heated to temperatures well above 500 °C without arsenic loss from the GaAs substrate. The physical, chemical, and electronic properties of the oxide are markedly changed by laser processing.
Model for mobility fluctuation 1/f noise
Authors: Jindal R. P. , van der Ziel A.
Published: February 2003

Hooge’s mobility fluctuation 1/f noise is interpreted in terms of fluctuations in the free path length of the carriers. The model involves a well-known distribution of time constants that gives the 1/f spectrum. Kleinpenning’s conjecture that Hooge’s original mobility fluctuation expression holds for individual energy intervals of the electrons is not vindicated. The free-path-length fluctuation is interpreted in terms of interactions of electrons with the slowly varying longitudinal phonon population of the sample, so that only the lattice mobility is noisy. Hence the model leaves the Hooge-Vandamme extension of Hooge’s original expression intact.
Fast compact optical waveguide switch modulator
Authors: Alferness R. C. , Economou N. P. , Buhl L. L.
Published: February 2003

We describe a very short (750 μm) laterally compact (1 μm electrode gap) optical directional coupler switch made with Ti-diffused lithium niobate waveguides with a demonstrated switching time of 110 ps.
Shock-wave production and plasma motion in CO2-laser-irradiated targets
Authors: Goldstone P. D. , Benjamin R. F. , Schultz R. B.
Published: February 2003

We use visible-light, streaked shadowgraphy to make to first measurements of several transport and expansion phenomena in CO2-laser-irradiated foils. Measured velocities of the free-surface motion, produced by the laser-driven shock wave, at the foil’s rear surface yield shock pressures in reasonable agreement with theory. The velocity of plasma expansion from the absorption region is observed to change abruptly after ∼1.5 ns. We speculate that this effect is due to relaxation of the steepened plasma profile. Energy transport from the front to rear surface via the target’s edge, which complicated shock studies, is controllable with a simple shield.
Oscillation burst generation in transferred-electron devices with picosecond optical pulses
Authors: Carruthers T. F. , Weller J. F. , Taylor H. F. , Mills T. G.
Published: February 2003

Bursts of oscillations have been triggered in GaAs transferred-electron devices by picosecond optical pulses focused onto the region between the gate and anode. The oscillation frequency was varied between 6.7 and 10.5 GHz by changing the position of the optical spot. The burst duration depended logarithmically upon the optical input power, indicating a decay of the optically excited electron-hole plasma with a measured lifetime of 430 psec, and could be varied between 1.5 and 5.0 nsec.
Negative ion losses in magnetically insulated vacuum gaps
Authors: VanDevender J. P. , Stinnett R. W. , Anderson R. J.
Published: February 2003

Negative ion losses have been observed in a long, self-magnetically insulated transmission line after the electrons are insulated. Time of flight spectra are consistent with H−, H2−, 02−, C2−, and heavier molecular ions with energies corresponding to the full anode-cathode potential difference. The negative ion current density Ji is a sensitive function of the conditions under which the cathode plasma is produced.
High-purity, single-crystal InP grown by synthesis solute diffusion
Authors: Engh R. O. , Peterson S. R. , Thorne J. P. , Petersen P. E.
Published: February 2003

Single-crystal InP was grown by the synthesis solute diffusion (SSD) technique. The measured etch pit density of ∼10 cm−2, mobility (77 K) of 50 200 cm2 V−1 s−1 and carrier concentration (77 K) of 2.3×1014 cm−3 demonstrate the feasibility of SSD for the growth of high-quality bulk InP.
Lateral epitaxy by seeded solidification for growth of single-crystal Si films on insulators
Authors: Fan John C. C. , Geis M. W. , Tsaur Bor-Yeu
Published: February 2003

By using a new method, which we have named the LESS technique (lateral epitaxy by seeded solidification), single-crystal Si films have been grown over insulating layers on single-crystal Si substrates. An amorphous or polycrystalline Si film is deposited on the insulating layer, in which narrow stripes have been opened to expose the substrate. By using two carbon strip heaters, one of which is movable, the Si film is melted and frozen in such a manner that solidification begins within the stripe openings, where it is seeded by the substrate. The resulting single-crystal regions in turn seed lateral single-crystal growth over the adjacent insulating layer. Continuous single-crystal Si films have been obtained over SiO2 layers with openings spaced 50 or 500 mm apart, and single-crystal growth extending as far as 4 mm over Si3N4 has been observed.
Plasma-enhanced thermal nitridation of silicon
Authors: Ito Takashi , Kato Ichiro , Nozaki Takao , Nakamura Tetsuo , Ishikawa Hajime
Published: February 2003

A new procedure for plasma-enhanced thermal nitridation of silicon is reported. Highly purified ammonia plasma is generated in a quartz tube by radio-frequency power heating induction-coupled and SiC-coated carbon susceptors. This system requires no additional electrode in the reaction environment. At a substrate temperature of 1050 °C, thermal silicon nitride films with a thickness above 100 Å are grown for 150 min in background pressures ranging from 10−1 to 10 Torr. The films have a refractive index of 1.90, oxygen contamination of less than 10%, and an etching rate two orders of magnitude smaller than that of a thermal SiO2 film in a solution of NH4F:HF = 7:1.
Formation of hot spots in a superconductor observed by low-temperature scanning electron microscopy
Authors: Eichele R. , Seifert H. , Huebener R. P.
Published: February 2003

Low-temperature scanning electron microscopy can be used for the direct observation of hot spots in a superconductor. Experiments performed at 2.10 K with tim films demonstrating the method are reported.
Low-loss GaAs optical waveguides formed by lateral epitaxial growth over oxide
Authors: Leonberger F. J. , Bozler C. O. , McClelland R. W. , Melngailis I.
Published: February 2003

We report the successful demonstration of a new type of single-mode semiconductor waveguide, an oxide-confined optical waveguide, that has lower loss and should have a smaller allowable bend radius than previously reported structures. The waveguides are formed by a new technique of lateral epitaxial growth of single-crystal GaAs over an SiO2 film. Rib waveguides formed on these epitaxial layers have SiO2 as the lower confining layer and thus have better confinement than comparable all-semiconductor structures. Losses of only 2.3 dB/cm (0.54 cm−1) have been measured at 1.06 mm.
Capillaritron: A new, versatile ion source
Authors: Mahoney John F. , Perel Julius , Forrester A. Theodore
Published: February 2003

The Capillaritron is an ion source consisting of a very fine bore capillary and a concentric accelerating electrode. When a gas flows through the capillary and a potential difference of several kilovolts is maintained between the capillary and an accelerating electrode, current densities exceeding 100 A/cm2 with angular current densities greater than 6 mA/steradian are obtained from a source aperture only 2.5 × 10−3 cm in diameter. The source has been tested with hydrogen, helium, and argon and appears capable of operating with any gas. A tentative theory based on the existence of a plasma inside the capillary, which is sustained by a small flow of electrons to the capillary from the beam, and a relatively large current released from the walls by excited atoms, appears consistent with observations.
Threshold conditions for laser-initiated plasma shutters
Authors: Czuchlewski S. J. , Figueira J. F.
Published: February 2003

The characteristics of laser-initiated plasma shutters used for retropulse isolation in high-power CO2 laser-fusion systems are discussed. Initiation of the plasma breakdown is shown to depend on the fluence that is incident on the edge of the iris which is employed in these shutters. A relatively simple model for the ignition process has been verified for a range of pulse durations (0.7–60 ns) and iris diameters (100–800 mm). This model provides practical design criteria for sizing plasma isolators for a variety of applications.
Kilowatt multiple-path 3He-Ar nuclear-pumped laser
Authors: DeYoung R. J.
Published: February 2003

Nuclear lasing of 3He-Ar at 2300-Torr total pressure with a thermal neutron flux of 4.3 × 1016 n/cm2 sec has resulted in a lasing output power of 1012 W. A multiple-path laser cavity was used with seven passes through the laser medium which was pumped by the 3He(n,p)3H nuclear reaction. The thermal neutron lasing threshold flux was 1 × 1016 n/cm2 sec. At 600-Torr 3He-(2%)Ar, the threshold flux was 4.7 × 1015 n/cm2 sec. This represents the highest-power, largest-volume nuclear laser to date.
UV hologram recording with an excimer laser
Authors: Brannon J. H. , Asmus J. F.
Published: February 2003

Ultraviolet hologram production using 353-nm radiation from an e-beam-pumped XeF laser is reported. Mode selection was accomplished via an unstable resonator. A description of the holographic optical configuration is detailed and the simplicity of the arrangement noted. Reconstruction was accomplished with a low-power He-Ne laser. Scene and reference optical path length differences of up to 15 cm produced no detectable change in hologram quality. Some advantages in using excimer lasers for UV holographic recording are presented.
Double-heterojunction laser diodes with multiply segmented contacts
Authors: Carney James K. , Fonstad Clifton G.
Published: February 2003

Multiple segment stripe contact (MSSC) diode lasers, in which the pumping current density, and thus the gain or loss, can be varied and controlled along the length of the laser stripe, are reported. For different combinations and magnitudes of current density into the eight segments, self-pulsing, optical switching, bistability, hysteresis, and extremely high external differential quantum efficiencies can each be achieved. By simultaneously monitoring the voltage on the individual segments, changes in the carrier concentration and thereby changes in the gain and loss as a function of optical density and position along the stripe have also been observed. The use of MSSC lasers in the study of basic laser diode properties as well as novel devices of interest in their own right is suggested.
Borosilicate glass films for InP encapsulation
Authors: Singh S. , Bonner W. A. , Camlibel I. , Grodkiewicz W. H. , Kyle T. R. , Pasteur G. , VanUitert L. G. , Williams R. S.
Published: February 2003

rf-sputtered borosilicate glass films were evaluated for surface protection of InP. The films, which have a thermal expansion coefficient much closer to InP than SiO2 or Si3N4, were usable up to ∼750 °C without cracking or peeling, and were also found to be effective masks for diffusion of Zn up to 650 °C and InP background doping in the 1×1016/cm range. The films were also found to be stable with respect to leaching of glass components by boiling water. Sputtered borosilicate glass films thus offer advantages over the use of SiO2, Si3N4 or phosphosilicate glass for use as an encapsulant on InP.
Influence of carrier diffusion on melt-front penetration during pulsed-laser annealing
Authors: Wood R. F.
Published: February 2003

It is shown that although carrier diffusion may increase the effective depth for energy absorption by the lattice during pulsed-laser annealing of semiconductors, it is unlikely that this increase will significantly alter the conclusions of the melting model of laser annealing.
Growth of extremely uniform layers by rotating substrate holder with molecular beam epitaxy for applications to electro-optic and microwave devices
Authors: Cho A. Y. , Cheng K. Y.
Published: February 2003

Integrated optics and integrated microwave circuits require extremely uniform epitaxial layer thicknesses, composition profiles, and doping profiles. With a sample rotating mechanism, molecular beam epitaxy can for the first time prepare GaAs and AlxGa1−xAs layers with thickness variation of less than 1% over a lateral dimension of 5 cm. The variation of AlAs mole fraction of the Al0.3Ga0.7As over a 10-cm2 area was less than 0.4%. The variation of the ’’pinch-off’’ voltage for a field effect transistor structure was less than 1.4% over a 10-cm2 wafer. These results represent the most uniform epitaxial layers ever prepared with any crystal growth technology.
Transparent and highly oriented ZnO films grown at low temperature by sputtering with a modified sputter gun
Authors: Onishi S. , Eschwei M. , Wang W. C.
Published: February 2003

Transparent, pure c-oriented ZnO films have been deposited on various substrates utilizing a magnetron sputter gun. The design of the gun and of the sputtering system helps to keep the substrate surface free from charged particle bombardment and excessive heat by radiation. The substrate temperature can be maintained as low as 98 °C reducing the effects of thermal stress to a minimum. A comparison is made between the conventional planar magnetron system and the sputter gun. The design of the sputter gun has overcome some of the difficulties which have existed in standard planar magnetron sputtering. Sputtering parameters and results are discussed as well as the advantages of using a reactively sputtered zinc target over a zinc-oxide target.
Magnetization of compositionally modulated CuNi films
Authors: Zheng J. Q. , Falco Charles M. , Ketterson J. B. , Schuller Ivan K.
Published: February 2003

We report static magnetization measurements on the compositionally modulated ferromagnetic alloy Cu/Ni, which, contrary to earlier ferromagnetic resonance measurements, show the moment per Ni atom is reduced relative to pure Ni. The low-temperature magnetization is found to vary linearly with modulation amplitude, but, surprisingly, the Curie temperature is found to be almost amplitude independent.
Volatile metal-oxide incorporation in layers of GaAs, Ga1−xAlxAs and related compounds grown by molecular beam epitaxy
Authors: Kirchner P. D. , Woodall J. M. , Freeouf J. L. , Pettit G. D.
Published: February 2003

A model is presented which relates the observed effects of substrate temperature and growth flux magnitudes upon layer quality to the presence of volatile oxides and the thermodynamics of the formation of nonvolatile oxides on the growth surface. A means for reducing oxide contamination is presented and the consequent benefits explored.
Photoluminescence study of native defects in InP
Authors: Temkin H. , Dutt B. V. , Bonner W. A.
Published: February 2003

A photoluminescence (PL) study of native defects and their distribution in polycrystalline ingots of melt-grown InP is reported. Three bands with peak positions at 0.99, 1.08, and 1.21 eV were found with systematic intensity changes along the length of the ingots. The PL bands were identified with the help of isothermal anneals as due to a donorlike P vacancy (0.99 eV), acceptorlike In vacancy or P interstitial (1.21 eV), and their complex (1.08 eV). The temperature dependence of the PL intensity compares well with the D-function potential model of Lucovsky.
Sulfur Doping in Al0.4Ga0.6As
Authors: Anthony P. J. , Zilko J. L. , Swaminathan V. , Schumaker N. E. , Wagner W. R. , Norberg J. C.
Published: February 2003

The incorporation of sulfur and measurements of its properties as a dopant in Al0.4Ga0.6As grown by liquid phase epitaxy at 780 °C are reported. Sulfur is readily incorporated, with a segregation coefficient of ∼100. However, sulfur creates deep centers in Al0.4Ga0.6As and produces low measured electron mobilities and increased nonradiative recombination. The unintentional incorporation of sulfur in (Al,Ga)As epillayers may result in the poor performance of devices due to compensation or type conversion of layers. The incorporation of sulfur in (Al,Ga)As can be reduced by interactions with the ambient gas during growth.
Measurements of submicron hole diffusion lengths in GaAs by a photovoltaic technique
Authors: Dorantes-Dávila J. , Lastras-Martínez A. , Raccah P. M.
Published: February 2003

A simple technique for measuring submicron diffusion lengths in semiconductors is described. It consists, basically, in measuring the photocurrent of a Schottky barrier as a function of applied reverse bias. The modification of the photoresponse due to electroabsorption effects in the barrier region has to be taken into account and is discussed here. The diffusion length of n-type GaAs doped at a concentration of 2.7×1017/cm3 is found to be 0.23 mm.
Luminescence investigations of laser-annealed Si
Authors: Mizuta M. , Sheng N. H. , Merz J. L.
Published: February 2003

Low-temperature photoluminescence has been used as a minority-carrier probe to investigate the perfection of laser-annealed Si. For cw laser annealing of ion implantation damage, the range of laser power over which good quality annealed material can be achieved, as determined by the relative luminescence efficiency, is limited. At high laser power, when laser-induced damage has been observed by other techniques, a slight broadening and shifting of the bound-exciton luminescence lines was seen. From these data, the residual strain surrounding the implanted ions was found to be small for the low doses employed in this study, with lattice displacements of less than ∼0.01%. These results imply that laser annealing can give rise to high-quality material suitable for device application if sufficient care is exercised.
Front surface control of Cr redistribution and formation of stable Cr depletion channels in GaAs
Authors: Magee T. J. , Ormond R. D. , Evans C. A. , Blattner R. J. , Malbon R. M. , Day D. S. , Sankaran R.
Published: February 2003

A technique has been investigated for creating sharply defined (near-surface) ’’square-well’’ Cr-depletion channels in GaAs with subsequent stability of Cr to anneal temperatures of 850 °C. Using 100-keV B+ implants into surface-ionized GaAs, followed by annealing (capless) at temperatures <800 °C in arsine, we observed depletion of Cr across the B- implantation profile from levels of ≃1017 to ≃3×1015 atoms/cm3. A flat depletion channel is formed, defined by a relatively abrupt shoulder and a maximum channel width of ≃1 mm. Hall effect and C-V profiles showed n-type conduction across the channel and Hall mobilities of ≃5200 and ≃11 600 cm2/V sec at 300 and 77 ° K, respectively. Measured carrier concentrations were in agreement with secondary-ion mass spectroscopy measurements of bulk donor impurity levels.
Laser annealing of ohmic contacts on GaAs
Authors: Oraby A. H. , Murakami K. , Yuba Y. , Gamo K. , Namba S. , Masuda Y.
Published: February 2003

Backside irradiation through the substrate with a Q-switched Nd:glass laser (l = 1.06 mm) has been used to produce Au-Ge ohmic contacts on GaAs. Conventional thermal alloying was done for comparison. The structure of the contacts was investigated by 2-MeV He-ion Rutherford backscattering technique, photographs, and I-V characteristic measurements. The irradiated Au-Ge contacts exhibit good ohmic contact behavior and good surface morphology. Ohmic contacts with specific contact resistance rc less than 2×10−5 W cm2 have been measured within the laser energy density of 0.3–0.5 J/cm2, while the thermally alloyed contacts yielded rc = 1.3×10−4 W cm2.
High-power microwave generation from a rotating E layer in a magnetron-type waveguide
Authors: Destler W. W. , Weiler R. L. , Striffler C. D.
Published: February 2003

The generation of high-power bursts of microwave radiation from hollow, relativistic E layers injected through a cusped magnetic field into a magnetron-type conducting boundary configuration has been studied experimentally. Using a 2-MeV, 2-kA, 5-ns injected beam pulse, approximately 250 MW of radiated power have been generated at 9.6 GHz.
Expansion of a cold ion cloud
Authors: Holm Darryl D. , Johnson Stevens F. , Lonngren Karl E.
Published: February 2003

For a class of initial conditions, the Cauchy problem is studied for electrostatic fluid equations that describe expansion of a cloud of ions in one dimension. The fluid motion which results is a type of free streaming of charged particles in a self-consistent electrostatic field. The exact solution obtained in planar geometry is compared with self-similar solutions and with previous investigations.
Low-(Delta)n-twisted nematic cell with improved optical properties
Authors: Pohl L. , Weber G. , Eidenschink R. , Baur G. , Fehrenbach W.
Published: February 2003

It is demonstrated by model calculations and experimental results, that the range of viewing angles of a twisted nematic (TN) display can be considerably improved by using a liquid-crystal material with a low refractive index anisotropy Dn<0.1.
Time-resolved optical transmission of pulsed laser-irradiated silicon
Authors: Lee M. C. , Lo H. W. , Aydinli A. , Compaan A.
Published: February 2003

The time-resolved optical transmission of silicon has been observed at l = 1.15 mm during irradiation by an 8-nsec pulsed laser at 485 nm with several energy densities in the range of 0.25 to 1.2 J/cm2. The transmission exhibits a sudden brief drop consistent with the rise and fall of the reflectivity enhancement. However, the transmission does not exhibit the strong absorption expected of molten silicon with a skin depth of ∼100 Å.
Deposited silica waveguide for intergrated optical circuits
Authors: Izawa Tatsuo , Mori Hidefumi , Murakami Yasuji , Shimizu Nobuo
Published: February 2003

Embedded single and multimode waveguides on fused quartz substrates have been fabricated by high-speed silica deposition and accurate reactive sputter etching by a C2F6 gas plasma. These waveguides have rectangular cross sections with an aspect ratio close to unity. Total waveguide loss was approximately 5 dB/cm, and absorption loss measured by laser calorimetry at 637-nm wavelength was less than 0.1 dB/cm.
Turnable cw bulk semiconductor platelet laser
Authors: Roxlo C. B. , Bebelaar D. , Salour M. M.
Published: February 2003

We report the first tunable laser action of a platelet semiconductor in an external cavity. We have achieved cw output powers of up to 9 mW from a CdS platelet optically pumped by an Ar+ laser at 476 nm. The energy conversion efficiency is 10% into the TEM00 mode. Tunability of the laser output was demonstrated from 495 to 501 nm using an intracavity prism with the crystal kept at a temperature of 95 K. Additional tuning to 504 nm was achieved by varying the temperature to 140 K.
Elimination of out-diffused surface guiding in titanium-diffused LiNbO3
Authors: Jackel J. L. , Ramaswamy V. , Lyman S. P.
Published: February 2003

We describe a means of eliminating undesired surface guiding in titanium-diffused strip waveguides on LiNbO3. Surface guiding for light of the extraordinary polarization, normally produced when the crystal is diffused in dry argon or oxygen, can be eliminated entirely by adding water vapor to the diffusion gases. Infrared absorption measurements show that hydrogen enters crystals diffused in a wet atmosphere. Although the mechanism for the prevention of surface guiding is not fully understood, we suggest that the presence of excess hydrogen reduces lithium mobility.
Acoustic microscopy of curved surfaces
Authors: Weglein R. D.
Published: February 2003

To date, imaging and metrology in the acoustic microscope have been performed exclusively on planar specimens. While imaging is accomplished by raster scanning in the plane transverse to the axis of the acoustic beam, metrology is practiced by variation of the specimen-lens separation along the beam axis. This operation yields an acoutic material signature at a single location on the specimen plane. The two modes of operation are in effect simultaneously employed when a nonplanar surface of known curvature is scanned. The resulting images reveal concentric rings with radial periodic brightness variation if the surface is spherical in shape. The technique is demonstrated with stainless-steel bearing balls of the type used in precision gyros. The application of this technique to the diagnostic inspection and analysis of both bearing balls and raceways are discussed. It is suggested that the obtained images represent a two-dimensional map of elastic properties of the bearing surface regions.
A laser-initiated, gas-embedded Z pinch: Experiment and computation
Authors: Jones L. A. , Finken K. H. , Dangor A. , Källne E. , Singer S. , Lindemuth I. R. , Brownell J. H. , Oliphant T. A.
Published: February 2003

Measurements done on a new plasma device, a laser initiated, gas-embedded Z pinch, are compared with magnetohydro dynamics(MHD) calculations. The measurements, which include two-foil x-ray absorption, absolute continuum emission, and schlieren shadowgraphy, are in good agreement with predictions made by a two-dimensional MHD calculation, which indicates that the peak electron temperature in the plasma is 200 eV and the peak electron density is 1×1020 cm−3.
Surface compositional modifications during O+2 bombardment of binary alloys
Authors: Yu Ming L. , Reuter Wilhad
Published: February 2003

Surface compositional modifications of binary alloys during 15-keV O+2 bombardment under 45° incidence were studied using Auger electron spectroscopy under ultrahigh vacuum conditions. For A1-Ni, Cr-Ni, Fe-Ni, and Pd-Ni alloys, the reactive preferential sputtering by O+2 causes a surface enrichment of the alloy component which has the smaller metal-oxygen bond energy per metal atom. For Cu-Ni and Ag-Pd alloys, where oxidation by the O+2 beam was slight, the surface compositions after O+2 bombardment were qualitatively similar to those caused by nonreactive preferential sputtering with Ar+.
Generation of surface gratings with periods < 1000 Å
Authors: Johnson L. F. , Ingersoll K. A.
Published: February 2003

Simple techniques for doubling the spatial frequency of surface-relief gratings are demonstrated. Grating periods as small as 750 Å have been produced and further subdivision appears possible.
High-purity ZnSe grown by liquid phase epitaxy
Authors: Werkhoven C. , Fitzpatrick B. J. , Herko S. P. , Bhargava R. N. , Dean P. J.
Published: February 2003

A study was performed to establish the origin and nature of background compensating impurities in undoped ZnSe layers grown by liquid phase epitaxy on ZnSe substrate wafers in a low-contamination-level environment. The width of bound exciton lines in low-temperature photoluminescence spectra was used to define the quality of the material, and the energy of the lines was used to identify these low-level impurities. The sharpest spectra occurred in layers grown rapidly on a previously grown buffer layer indicating the importance of impurity outdiffusion from the substrate into the growing layer. The sharpness of these bound exciton lines indicates that the total concentration of electrically active impurities (NA+ND) is <1017/cc, an estimate which is confirmed by mass spectroscopy.
Preferential sputtering of Si3N4
Authors: Bhattacharya R. S. , Holloway P. H.
Published: February 2003

Auger peaks of 82-eV Si and 381-eV N have been used to study the preferential enrichment of one component of Si3N4 after sequential sputtering with 0.5- and 2.0-keV Ar+ and He+ ions. The results clearly indicate that the element enriched at the surface, due to sputtering, depends on the mass of the impinging ion, and the magnitude of the enrichment depends on the energy of the ion. For example, N was enriched by Ar+, while Si was enriched by He+ bombardment. These results are explained by considering direct knockoff and energy transfer processes in sputtering.
Interface polarization in silicon on sapphire
Authors: Krusius P. , Dube C. , Frey J.
Published: February 2003

The silicon-on-sapphire (SOS) interface has been studied using a new approach based on the use of the mechanically thinned sapphire as a metal insulator semiconductor gate insulator. A final sapphire thickness of 5 mm has been achieved. 1-MHz capacitance-voltage profiles exhibit a pronounced hysteresis, which is investigated using electrical and thermal stress, time-resolved capacitance and laser-induced photocapacitance. A native polarizable interfacial layer in SOS is shown to be the possible mechanism for the observed hysteresis. An interface model including a polarizable layer (equivalent to a reduced charge of the order of 1011 e/cm2), interface states (at midgap 1×1012 states/cm2/eV), and fixed charges is presented.
Reactive ion etching of GaAs in CCl2F2
Authors: Klinger R. E. , Greene J. E.
Published: February 2003

The reactive ion etching of (100) GaAs in CCl2F2 and mixed CCl2F2+Ar discharges has been investigated. Anisotropic etching with removal rates R of 0.8 mm/min have been obtained in pure CCl2F2 discharges operated at 5.3 Pa (40 mTorr) and −3 kV, whereas the physical sputtering rate in pure Ar discharges under these conditions was only 0.04 mm/min. A combination of optical emission and absorption spectroscopies have been used to show that in CCl2F2 and even in dilute 10% CCl2F2+90% Ar discharges operated under the same conditions, physical sputtering is not a primary etching mechanism for GaAs, although is is important for minimizing residual carbon accumulation. Rather, etching is believed to occur by the formation and desorption of Ga and As halides with the rate limiting step being the removal of GaF3. The kinetics of this process are aided by ion-bombardment-enhanced diffusion and stimulated desorption.
Luminescence of thermally induced defects in Si crystals
Authors: Nakayama H , Nishino T , Hamakawa Y
Published: February 2003

Thermally induced defects in Si crystals annealed at low temperatures around 500 °C have been investigated by photoluminescence measurements. It has been found that photoluminescence spectra of annealed Si crystals strongly depend on the concentrations of oxygen and carbon impurities. Many sharp luminescence lines, whose spectral energy positions and temperature behaviors are quite different from those of the usual bound-exciton luminescence, have been found for the first time. Furthermore, strong, broad luminescence bands have been observed for annealed CZ-Si with high oxygen and low carbon contents.
Proximate capless annealing of GaAs using a controlled-excess As vapor pressure source
Authors: Woodall J. M. , Rupprecht H. , Chicotka R. J. , Wicks G.
Published: February 2003

A new, capless annealing technique for GaAs, which utilizes a controlled-excess arsenic vapor pressure has been studied. The excess arsenic vapor is provided by the thermal decomposition of InAs and is about 100 times larger than the arsenic pressure of thermally decomposing GaAs for temperatures of 800–900 °C. This excess pressure forces Si implants to activate predominantly on donor sites for doses of (2–50)×1012 cm−2 studied thus far. A SiF+ dose of 5×1012 cm−2 and implant energy of 250 keV annealed at 900 °C for 30 min produced a sheet electron concentration of 3.5×1012 cm−2 and mobility of 4400 cm2 V−1 sec−1. Photoluminescence studies show that the annealed surfaces must be proximate during anneal to avoid buildup of impurities at the surface. A model based on GaAs evaporation and buildup of bulk impurities on the surface is proposed to explain the results.
Fabrication of periodic waveguides by ion exchange
Authors: Pun E. Y. B. , Yi-Yan Alfredo
Published: February 2003

Periodic waveguides have been fabricated by diffusing silver ions into soda lime glass substrates through aluminium grating masks. An efficient beam splitter has been demonstrated. The technique is simple to implement and could be used to fabricate other efficient thin-film devices.
Electron paramagnetic resonance spectroscopy with photothermal and optoacoustic detection
Authors: DuVarney R. C. , Garrison A. K. , Busse G.
Published: February 2003

Electron paramagnetic resonance (EPR) spectroscopy has been performed using optoacoustic piezoceramic detection and photothermal infrared detection. Though the signal-to-noise ratio is lower than in conventional EPR detection at 100 kHz, it compares favorably at low modulation frequencies. These detection techniques offer the opportunity of obtaining EPR depth profiles that cannot be obtained using the conventional technique.
Deep levels associated with nearest-neighbor substitutional defect pairs in GaAs
Authors: Sankey Otto F. , Dow John D.
Published: February 2003

A simple model calculation of the deep energy levels produced by pairs of nearest-neighbor substitutional defects in GaAs is presented. The deep levels of a1 and e symmetry for 841 sp3-bonded defect-pair combinations are predicted.
Influence of an undoped (AlGa)As spacer on mobility enhancement in GaAs-(AlGa)As superlattices
Authors: Störmer H. L. , Pinczuk A. , Gossard A. C. , Wiegmann W.
Published: February 2003

The introduction of an undoped (AlGa)As spacer enhances significantly the low-temperature mobility in modulation-doped GaAs-(AlGa)As superlattices. Mobilities increase monotonically with spacer thickness. This indicates that ionized impurity scattering can be further suppressed by increasing the separation between carriers and their parent donors. Hall mobilities of 93 000 cm2/V sec were observed for average Hall densities of 4.9×1016 cm−3 at 4.2 K.
Saturation effects of cathodoluminescence in rare-earth activated epitaxial Y3Al5O12 layers
Authors: van der Weg W. F. , van Tol M. W.
Published: February 2003

The intensity of luminescence in YAG, activated with rare-earth ions, shows a nonlinear behavior as a function of incident current density under electron bombardment. Tb3+ or Eu3+ activated samples exhibit deviation from linearity at input power densities exceeding 104 W/m2, while Ce3+ luminescence is linear up to the highest power densities studied (108 W/m2). It is shown that nonlinearity effects, in cases where temperature quenching can be excluded, are caused by saturation of the excited-state population. The results are interpreted in a model which also takes into account excited-state absorption within one activator and energy transfer between neighboring activator ions.
Molecular beam epitaxial GaAs-AlxGa1-xAs heterostructures for metal semiconductor field effect transistor applications
Authors: Wang W. I. , Judaprawira S. , Wood C. E. C. , Eastman L. F.
Published: February 2003

High-quality GaAs-AlxGa1-xAs heterostructures for metal semiconductor field effect transistor (MESFET) applications have been grown by molecular beam epitaxy. 0.5-μm-thick n-type GaAs active layers with free-carrier concentrations ∼1.1×1017 cm−3 and room-temperature electron mobilities ∼4400 cm2 V−1 sec−1 were routinely obtained on top of undoped AlxGa1-x As (x∼0.4) buffer layers. MESFET’s fabricated on these layers showed approximately 2000-Ω-mm output resistance.
Electrolyte-oxide-semiconductor junction at the p-InP/V 2+-V 3+ interface
Authors: Menezes S. , Lewerenz H. J. , Thiel F. A. , Bachmann K. J.
Published: February 2003

Voltammetric measurements show that a thin passivating film exists at the p-InP/V2+-V3+ electrolyte interface, which allows efficient minority-carrier collection via tunneling. An electrolyte-oxide-semiconductor energy band diagram is presented that explains the properties of the p-InP/V2+-V3+, 4-M HCl/C solar cell.
Extension of lasing wavelengths beyond 0.87 μm in GaAs/AlxGa1−xAs double-heterostructure lasers by In incorporation in the GaAs active layers during molecular beam epitaxy
Authors: Tsang W. T.
Published: February 2003

We demonstrate that the lasing wavelengths of GaAs/AlxGa1−xAs double-heterostructure (DH) lasers can be extended beyond 0.87–0.94 μm without significant increase in the current threshold by incorporating In into the GaAs active layer during molecular beam epitaxy. This shift permits the benefits of reduced optical fiber loss and wavelength multiplexing with 0.83 μm and using the same fibers. A reduction in averaged current-threshold density (from 800 to 700 A/cm2) was obtained in those InGaAs/AlGaAs DH lasers that have the InGaAs active layer exactly lattice-matched to the AlGaAs cladding layers. As a result of the stress relief at the lattice-matched InGaAs/AlGaAs interfaces of these DH lasers, it may be possible to improve the reliability of the lasers operating at 0.88 μm.
Collision-induced gain
Authors: Rogovin D. , Avizonis Petras
Published: February 2003

We present a novel scheme for achieving gain based on the notion of inducing a transient electric dipole moment in long-lived atomic or molecular metastable states via collision processes. As specific applications of this concept, we determine the induced gain for the I2P1/2(5p5) → 2P3/2(5p5) and the He1S0(1s2s) → 1S0(1s2) transitions for the case in which radiation emission is initiated by collisions with a molecular dipole.
Two-carrier nature of interface-state generation in hole trapping and radiation damage
Authors: Lai S. K.
Published: February 2003

In hole trapping and radiation damage in silicon dioxide, a characteristic interface-state peak is present. It is shown by the present work that the interface peak is due to trapping of holes at the silicon-silicon dioxide interface and the subsequent capture of injected electrons by the holes. It is postulated that dipolar complexes are formed, which give rise to electronic states at the interface. Similar dipoles may be responsible for neutral traps in the bulk of oxides after irradation.
New anomalous photocurrent peak of the TiO2−x thin film electrodes
Authors: Kim Wha-Tek , Choe Chu-Hyun , Won Choi Q.
Published: February 2003

A titanium oxide thin film (TOTF) has been prepared by reaction of titanium sheet (99.9%, 1/2 mm thick) with water vapor at 600 °C. The electrical conductivity is n type, and the resistivity is of about 10 Ω cm. The photoelectroylsis reveals that the TOTF responds to the light of three-spectral regions, one in 280–420 nm region corresponding to the well-known TiO2 band and others centered at 490 and 589 nm, respectively, which are hitherto not reported. The latter are assigned to the subband gap states responsible for reducing oxygen molecules at the TOTF-electrolyte interface.
X-ray photoelectron spectroscopic studies on ZnO-Sb2O3 varistors
Authors: Sainkar S. R. , Badrinarayanan S. , Sinha A. P. B. , Date S. K.
Published: February 2003

An x-ray photoelectron spectroscopy study of ZnO-Sb2O3 varistors was carried out in order to get an insight into the origin of the nonohmic behavior of the current-voltage characteristics observed in this device. It is found that this behavior is due to the migration of Sb2O3 to the surface. This migration starts at 500 °C and reaches a maximum at 660 °C. Above 900 °C, there is a spinel formation (Zn7Sb2O12), which is confirmed by x-ray diffraction and x-ray photoelectron data.
16-μm laser oscillation in propyne
Authors: Fischer T. A. , Wittig C.
Published: February 2003

An optically pumped propyne laser with tunable output in the 609–637-cm−1 region is reported. The pump source is a transverse electric atmosphere CO2 laser, and 16-μm laser energies as high as 6 mJ are obtained.
Waveform measurements on gigahertz semiconductor devices by scanning electron microscope stroboscopy
Authors: Fujioka Hiromu , Ura Katsumi
Published: February 2003

Waveform measurements on the semiconductor devices with the stroboscopic scanning electron microscope are reported, for the first time, in the gigahertz region. Waveforms of the high-field domains in a Gunn-effect diode triggered at 1 GHz are clearly measured with a time resolution of 5 ps.
Heterogeneous nucleation of damage in crystalline silicon with picosecond 1.06-μm laser pulses
Authors: Sheng D. Y. , Walser R. M. , Becker M. F. , Ambrose J. G.
Published: February 2003

The heterogeneous nature of the nucleation and growth of damage induced by ;picosecond Nd:YAG laser pulses in single-crystal silicon has been demonstrated. A damage kinetic model analogous to the conventional theory of nucleation and growth is used to analyze experimental results. The analysis shows that the damage kinetics has a critical dependence on the incident intensity.
Giant stark broadening of atomic gallium emission lines near a high field tip
Authors: Venkatesan T. , Wagner A. , Nash D. L. , Mungo A. J. , Barr D.
Published: February 2003

The optical spectrum of gallium atoms produced and excited near a self-formed high-field emission tip of a liquid metal gallium ion source has been observed in detail. The spectrum reveals several interesting features. The dispersed neutral gallium lines exhibit asymmetric tails extending over tens of angstroms. The broadening is identified as due to quadratic stark effect. The maximum broadening is limited by field ionization of the atom from its excited state. The agreement with classical results is reasonable. A background continuum has also been observed, which may be due to transition radiation arising from collision of electrons, produced during field ionization, with the liquid-metal tip.
Bombardment-induced corrosion resistance of aluminum
Authors: Pankove J. I. , McGinn J. T. , Wu C. P.
Published: February 2003

Ion bombardment of aluminum films at doses greater than 3×1014 cm−2 inhibits the etching of aluminum by acids. Ions of B, P, N, Si, Al, As, and Ar are effective inhibitors. Bombardment randomizes the orientation of microcrystals; however, this may not be the primary reason for the observed corrosion resistance.
The crystallographic orientation of A15 V3Ga and Nb3Al precipitates in B
C
C matrices
Authors: Wu I. -W. , Hong M. , Morris J. W.
Published: February 2003

Convergent-beam transmission electron diffraction was used to determine the crystallographic orientation of submicron-sized A15 structure V3Ga and Nb3Al precipitates formed by solid-state precipitation from supersaturated BCC solutions. In each case the crystallographic orientation relation was (to within an uncertainty of ±5°): [001]A15∥[111]BCC; (100)A15∥(11̄0)BCC. This lattice correspondence is intuitively plausible, since it ensures that the closest packed planes and directions of the precipitate parallel to those of the matrix.
Improvement in the width of superconducting transition ΔT
c of Nb3Ge by small mechanical shock
Authors: Watanabe Takumi , Obara Kōzō , Ōgushi Tetsuya , Numata Tadashi , Anayama Takeshi
Published: February 2003

A small mechanical shock (∼10 kPa) was applied to sputtered Nb3Ge films at room temperature. The superconducting transition temperature Tc of the films has been measured, and remeasured after application of the shock. The results confirm that the small mechanical shock improves Tc and Tce (lower onset) markedly. Changes in the lattice parameter and improvement in the structural ordering of the high-Tc A-15 phase after application of the shock have been observed from the results of x-ray measurements.
Efficient second-harmonic generation of Nd:YAG laser radiation using warm phasematching LiNbO3
Authors: Byer R. L. , Park Y. K. , Feigelson R. S. , Kway W. L.
Published: February 2003

Warm phasematching LiNbO3 (Tpm ∼120 °C) has been used to achieve greater than 40% SHG efficiency of an acousto-optic Q-switched Nd:YAG laser. The growth of high-quality LiNbO3 crystals suitable for efficient noncritical second-harmonic generation is possible owing to the significantly lowered index damage annealing temperature.
XeF excimer laser pumped in a longitudinal low-pressure discharge
Authors: Burkhard P. , Gerber T. , Lüthy W.
Published: February 2003

Results of a new excitation technique for excimer lasers are reported. The B→X band of Xef at 352 nm has been pumped in a longitudinal low-pressure discharge. Low-power, 20-nsec laser pulses of high beam quality have been generated.