bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-heated thermocouples for far-infrared detection
Authors: Neikirk Dean P. , Rutledge David B.
Published: February 2003

A novel self-heated Bi-Sb thermocouple for far-infrared detection has been developed. The detector is suitable for integration with monolithic antennas and imaging arrays. The device is fabricated in a single photolithography masking step using a photoresist-bridge technique. This bridge technique has also been used to make microbolometers with lower 1/f noise than those made by two conventional masking steps. The thermocouples have a noise equivalent power (NEP) of 7×10−10 W/(√Hz) and a 3-dB frequency response of 150 kHz.
Flash x radiography of laser-accelerated targets
Authors: Whitlock R. R. , Obenschain S. P. , Grun J.
Published: February 2003

Flash x radiography of ablatively accelerated planar foils has provided quantitative measurements and qualitative observations regarding several parameters of critical interest to direct illumination laser fusion. A 1.05-μ, 3.3-ns driver beam was focused onto carbon foils in a large (0.7–1-mm diameter) spot to reduce edge effects. From images produced by a backlighting x-ray flash, we have measured overall coupling efficiency, smoothing of laser nonuniformities, target velocity, and ablation pressure. The high velocity targets maintain a localized, high density (≳3% of solid). In contrast to other workers’ recent measurement of pressure from x-ray imaging, our x-radiographic results, including pressure, are in general agreement with earlier NRL studies. Our results have also provided further insights into double foil interactions and planar target preheat measurements.
Two-dimensional interferometric imaging of moving plasma disturbances in the ZT-40M reversed-field pinch, using time-delayed correlation techniques
Authors: Jacobson Abram R. , Forman Peter R.
Published: February 2003

An eight-chord interferometer array, together with a single-chord interferometer separated toroidally by 90°, shows propagating global plasma density disturbances in the final 1 ms prior to discharge termination in ZT-40M. A time-delayed correlation technique applied to the nine-chord data allows reconstruction of the shape of the propagating disturbance and discriminates against competing random density fluctuations.
First nucleation rule for solid-state nucleation in metal-metal thin-film systems
Authors: Bené R. W.
Published: February 2003

We extend our previous considerations of low-temperature phase nucleation in transition metal (Tm) silicon systems to thin-film metal-metal systems. We particularly concentrate on the similarities and differences between Tm-Si (and Tm-Ge) systems and metal-metal systems. Most of the metal-metal low-temperature reaction data has been previously presented in an article by Campisano, or in the book by Baglin and Poate, which we have reorganized and discussed in terms of a rule for first phase nucleation for these systems. Finally, we suggest a model for Pd80 Si20 glass formation in terms of the general model recently introduced by Phillips.
Mobility enhancement in modulation-doped GaAs/AlAs heterostructures grown by molecular beam epitaxy
Authors: Wang W. I.
Published: February 2003

Modulation-doped GaAs/AlAs heterojunctions have been successfully grown for the first time. Liquid nitrogen electron mobility in excess of 100 000 cm2 V−1 s−1 has been obtained at a sheet electron concentration of 3.27×1011 cm−2. The interface properties studied by reflection electron diffraction are consistent with results of electrical measurement. The advantages of modulation-doped structures with high aluminum concentrations are discussed.
Enhanced nonlinear birefringence in hybrid aligned nematics
Authors: Barbero G. , Simoni F.
Published: February 2003

We show that birefringence can be optically induced in hybrid aligned nematic (HAN) liquid crystals at normal incidence for light fields much lower than the Fredericksz threshold. In this case no threshold exists and the nonlinear optical effect at normal incidence is of the same order as that obtained with homeotropic (HOM) cells for the maximum useful angle. An analysis of the effect of the anchoring energy Ws is worked out showing that weak anchoring on the walls enhances the nonlinear effect by one order of magnitude or more.
Optical switching in semiconductor organic thin films
Authors: Potember R. S. , Poehler T. O. , Benson R. C.
Published: February 2003

Semiconducting organometallic films such as copper tetracyanoquinodimethane (CuTCNQ) have been observed to switch between two stable states when exposed to optical radiation. Observations of switching between two states in these films have been made by Raman spectroscopic methods and direct observation of electrical resistance changes. Line or pattern generation is observed for exposure above certain threshold levels. These effects are observed in a wide range of Cu and Ag organometallic compounds.
High-efficiency organometallic vapor phase epitaxy AlGaAs/GaAs monolithic cascade solar cell using metal interconnects
Authors: Ludowise M. J. , LaRue R. A. , Borden P. G. , Gregory P. E. , Dietze W. T.
Published: February 2003

A two-junction solar cell has been fabricated using an Al0.30Ga0.70As (1.82 eV) tap cell and a GaAs (1.43 eV) bottom cell. A processed metal interconnect is used to connect the two cells together in series. An efficiency of 21.5% at 980 mW/cm2 has been measured in a solar simulator with an open circuit voltage of 2.35 V, a short circuit current of 118.6 mA/cm2, and a fill factor of 0.76. An efficiency of 22% has been measured under 130 AM3 sun in a solar tracking concentrator. Organometallic vapor phase epitaxy is used to grow the entire nine-layer device.
Self-developing photoetching of poly(ethylene terephthalate) films by far-ultraviolet excimer laser radiation
Authors: Srinivasan R. , Mayne-Banton V.
Published: February 2003

Radiation of 193-nm (ArF excimer laser) wavelength can cause the etching of surfaces of poly(ethylene terephthalate) (PET) films in a controlled manner without any subsequent processing. Etch rates of 1200 Å/pulse of 370 mJ/cm2 were realized in air. The reaction can be attributed to (ijk) the high absorption cross section of the films for the radiation which results in the energy being trapped in the first 2700 Å, (ii) the high efficiency for bond breaking at these photon energies, and (iii) the formation of numerous small fragment molecules which promotes their volatization. The process is observed in a vacuum but is considerably modified in the presence of air.
Nonlinear luminescence and time-resolved diffusion profiles of photoexcited carriers in semiconductors
Authors: Olsson A. , Erskine D. J. , Xu Z. Y. , Schremer A. , Tang C. L.
Published: February 2003

We describe a new and general optical technique for studying carrier dynamics in semiconductors which is based on the luminescence nonlinearity resulting from the bimolecular recombination of the carriers. The technique has been used to obtain time-resolved diffusion profiles and the hole mobility in photoexcited GaAs.
Role of dangling bonds and antisite defects in rapid and gradual III-V laser degradation
Authors: Dow John D. , Allen Roland E.
Published: February 2003

Based on calculations of deep trap energies, it is proposed that the rapid (∼1 h) degradation of high-radiance (≳1018 carriers/cm3) Ga-rich III-V semiconductor lasers proceeds through self-reproducing dangling bond deep traps generated as a result of nonradiative recombination. This degradation mechanism can be inhibited by constructing lasers from alloys whose dangling bond energy levels do not lie within the fundamental band gap. The gradual (∼106 h) III-V laser degradation is tentatively associated with recombination events at an anion-on-cation-site deep trap.
Toward quantum well wires: Fabrication and optical properties
Authors: Petroff P. M. , Gossard A. C. , Logan R. A. , Wiegmann W.
Published: February 2003

As a first step toward the realization of a one-dimensional carrier confining structure in semiconductors, we have fabricated GaAs quantum well wires (QWW) with submicron dimensions using molecular beam epitaxy of GaAs and Ga1−xAlxAs. The structural quality and dimensions of the QWW have been assessed by transmission electron microscopy showing that single crystal, defect-free QWW, with dimensions as small as 200×200 Å in cross section can be achieved. The optical properties measured by low-temperature (T≳20°K) cathodoluminescence (CL) indicate a CL efficiency nearly as good as that of the quantum well material from which the QWW originated. A localization of the luminescence along the QWW axis is characteristic of QWW with sizes below a critical dimension (1.5 μm×200 Å cross section). This luminescence localization and a shift of the intrinsic luminescence to lower energy in QWW structures are tentatively assigned to strain effects in these structures.
Extended gas lifetime operation of a miniature transversely excited atmosphere CO2 laser doped with tripropylamine
Authors: Marchetti R. , Penco E. , Armandillo E. , Salvetti G.
Published: February 2003

Long life (≳106 shots), sealed operation of a repetitively pulsed (4 pps), compact (5-cm3 active volume), transversely excited atmosphere (TEA) CO2 laser has been achieved using an efficient corona-type preionization and traces of tripropylamine (TPA) as gas additive. The use of TPA has enabled extended operation with a maximum output peak power of about 350 kW.
Proton exchange for high-index waveguides in LiNbO3
Authors: Jackel J. L. , Rice C. E. , Veselka J. J.
Published: February 2003

We describe the fabrication and characterization of optical waveguides formed in LiNbO3 by proton exchange in benzoic acid melts at 200–250 °C. Proton exchange, in LiNbO3 the replacement of lithium ions with protons, takes place when the substrate is immersed in the molten acid. We observe a surface increase in the refractive index of 0.12, for the extraordinary polarization only, with a step function index profile. This is the highest index increase obtainable to date for LiNbO3. Measured diffusion rates for x-cut crystals are 1.37 μm2/h at T = 249 °C and 0.37 μm2/h at T = 217 °C, so that very deep guides can be formed in short times. Diffusion is somewhat slower in the z direction. The process as described is not useful for y-cut crystals, since it damgaes this surface. Losses, measured on x-cut samples, were <0.5 dB/cm. All measurements were made at 0.633 μm.
Optical absorption coefficient of silicon at 1.152 μ at elevated temperatures
Authors: Jellison G. E. , Lowndes D. H.
Published: February 2003

The optical absorption coefficient of silicon has been measured at the HeNe near-infrared line (λ = 1.152 μm) from room temperature to 1140 K. The results are compared with the previous less extensive data in the literature, and with the formulation given by Macfarlane et al. [Phys. Rev. 111, 1245 (1958)]. It is found that the absorption is described very well by phonon-assisted indirect transitions across an energy gap having the temperature dependence described by Thurmond.
Frequency stabilization of a diode laser by use of the optogalvanic effect
Authors: Yamaguchi Shizuo , Suzuki Masao
Published: February 2003

The frequency of an AlGaAs diode laser has been stabilized to the center frequency of the optogalvanic signal corresponding to the 4s′01–4p12 (Racah notation) transition of Ar I at 8408.2094 Å. The first derivative curve of the line was used as the error signal to be fed back to the operating current source of the diode laser. Fluctuation of the laser frequency was within 200 kHz for several hours.
Passive stabilization scheme for fiber interferometers using (3×3) fiber directional couplers
Authors: Koo K. P. , Tveten A. B. , Dandridge A.
Published: February 2003

A passive stabilization scheme using a (3×3) fiber directional coupler in an all fiber Mach–Zehnder interferometer and suitable signal processing has been successfully demonstrated. A stable output with large signal dynamic range and a minimum detectable phase shift in the microradian range has been achieved.
Lateral diffusion of Ni and Si through Ni2Si in Ni/Si couples
Authors: Zheng L. R. , Hung L. S. , Mayer J. W. , Majni G. , Ottaviani G.
Published: February 2003

Lateral diffusion couples of Ni on Si layers and Si on Ni layers were used in conjunction with scanning electron microprobe measurements to investigate the growth of Ni silicides in the temperature range 400–700 °C. The phase Ni2Si grows proportional to (time)1/2 until a length of 25–30 μm (at 600 °C) where the phase sequence Ni5Si2, Ni2Si, Ni3Si2, and NiSi is observed. Both Ni and Si diffuse through Ni2Si with an effective diffusion coefficient D≃0.02 cm2/s ×exp[−(1.4±0.1) eV/kT]. The diffusion of Si was also observed by the growth of Ni2Si in Ni films at the periphery of contact openings in SiO2 layers on Si.
Palladium and platinum gate metal-oxide-semiconductor capacitors in hydrogen and oxygen mixtures
Authors: Armgarth M. , Söderberg D. , Lundström I.
Published: February 2003

A comparison is made between palladium (Pd) and platinum (Pt) as gates in metal-oxide-semiconductor devices in different hydrogen/oxygen mixtures. We have shown that Pd is superior as gate material for detection of small amounts of hydrogen in room ambient. At high hydrogen concentrations Pt would be more suitable.
Bulk formation of a metallic glass: Pd40Ni40P20
Authors: Drehman A. J. , Greer A. L. , Turnbull D.
Published: February 2003

Molten spheroids of Pd40 Ni40 P20, of up to 0.53-cm minor diameter, were slowly cooled (1.4 K/s) on a fused silica surface under 10−6 Torr vacuum to a form which was entirely glassy except for some superficial crystallinity comprising less than 0.5% of the volume. The occurrence of crystallization was eliminated by subjecting the specimens to surface etching followed by a succession of heating and cooling cycles. The absence of crystallization in the bulk was confirmed by x-ray diffraction, transmission electron microscopy, and calorimetry. Using the last technique, the heat of crystallization of the glass was measured to be 5.3±0.3 kJ/g atom.
Fe-B glasses formed by picosecond pulsed laser quenching
Authors: Lin Chien-Jung , Spaepen Frans
Published: February 2003

Using picosecond pulsed laser irradiation, Fe-B alloys have been melted and quenched into glasses, with a B content as low as 5 at. %, which is significantly less than the minimum 12-at. % B content required for glass formation by other liquid quenching techniques. Compositionally modulated films with wavelengths on the order of 20 Å were used as starting materials to ensure homogeneity of the melt after irradiation.
Large room-temperature optical nonlinearity in GaAs/Ga1−x AlxAs multiple quantum well structures
Authors: Miller D. A. B. , Chemla D. S. , Eilenberger D. J. , Smith P. W. , Gossard A. C. , Tsang W. T.
Published: February 2003

We report the first measurements of optical absorption saturation in GaAs/GaAlAs multiple quantum well (MQW) structures at room temperature near the heavy hole exciton peak. Linear absorption shows distinct exciton peaks at room temperature in the MQW and we deduce this is because the confinement increases exciton binding energy without increasing LO phonon coupling. This room-temperature MQW absorption also saturates more readily than that in a comparable GaAs sample; the measured saturation intensity is 580 W/cm2 with a recombination time of 21 ns in a MQW with 102-Å GaAs layers. From this we predict a nonlinear refraction coefficient n2∼2×10−5 cm2/W. This large nonlinearity should permit room-temperature optical devices compatible with laser diode wavelengths, materials and power levels.
Deep photoluminescence band related to oxygen in gallium arsenide
Authors: Yu Phil Won , Walters D. C.
Published: February 2003

Temperature-dependent photoluminescence and photoluminescence excitation spectroscopy have been used to measure the 0.63-eV luminescence band present in O-doped semi-insulating GaAs. It is shown that the 0.63-eV band is related to the presence of O. The center responsible for the band forms a deep level similar to the main deep donor EL2. However, spark source mass spectrometry indicates that incorporation of O into GaAs is difficult.
Room-temperature cw operation in the visible spectral range of 680–700 nm by AlGaAs double heterojunction lasers
Authors: Yamamoto S. , Hayashi H. , Hayakawa T. , Miyauchi N. , Yano S. , Hijikata T.
Published: February 2003

Room-temperature cw operation at the wavelength below 700 nm has been achieved by AlGaAs double heterojunction (DH) lasers with a novel structure, in which a thick buffer layer is grown and the substrate is removed. Continuous-wave threshold currents were 60–120 mA in the visible spectral range of 680–700 nm. Also the fundamental transverse and single longitudinal mode were obtained under cw operation. The shortest cw wavelength is 683 nm at the present time.
Nonlinear aspects of hydrodynamic instabilities in laser ablation
Authors: Emery Mark H. , Gardner John H. , Boris Jay P.
Published: February 2003

We report on our investigation of the Rayleigh–Taylor and Kelvin–Helmholtz (KH) instabilities in laser ablatively accelerated targets for a series of single mode perturbations. We find linear growth rates well below classical values and a cutoff in the growth rates for wavelengths less than the foil thickness. However, the striking result is the dominance of nonlinear effects, i.e., the KH rollup, for the short wavelength perturbations. Although the linear growth rate increases as k1/2 up to the cutoff, the KH rollup dominates at large k, drastically reducing the penetration rate of the dense spike below its free fall value in the nonlinear phase and effectively doubling the aspect ratio before foil breakup.
Auger and electron energy-loss study of the Al/SiC interface
Authors: Bermudez Victor M.
Published: February 2003

Auger and electron energy-loss spectroscopies, as functions of Al coverage and annealing temperature, have been used to determine the mechanism of formation of the Al/SiC interface. Al deposited at room temperature forms quasi-metallic islands randomly distributed over the surface. Annealing at moderate temperature (≤600 °C) causes aggregation of Al at C-rich sites. At higher temperature, Al reacts with C (but not with Si) to form Al4C3.
Nucleation and growth rate of a-Si alloys
Authors: Gonzalez-Hernandez Jesus , Tsu Raphael
Published: February 2003

From fitting the crystallization rate to an Arrhenius rate expression with a single activation energy we found that it is possible to distinguish a purely amorphous silicon sample from one having trace crystallinity. Whenever microcrystallites are present whether from heavy P doping or heat treatment, the ‘‘activation energy’’ is approximately 1 eV, whereas purely amorphous silicon has an activation energy of 3–4 eV. In other words, the exponent on time in the Avrami expression is different for the nucleation and growth processes.
12× pulse compression using optical fibers
Authors: Nikolaus B. , Grischkowsky D.
Published: February 2003

We report a factor of 12 compression of the 5.4-ps, 1-kW pulses from a mode-locked dye laser. The pulses were frequency broadened and linearly chirped by the combined action of self-phase modulation and group velocity dispersion during passage through a 30-m single-mode optical fiber. The fiber output pulses were then compressed to 450-fs, 3-kW pulses by passage through a diffraction grating based dispersive delay line. These short pulses were tunable over the 300-Å range of the laser dye.
Photoacoustic generation and detection of 10-ns acoustic pulses in solids
Authors: Tam A. C. , Coufal H.
Published: February 2003

We describe the generation and detection of short acoustic pulses (∼10-ns widths) in opaque plates, using weak laser pulses (less than 1-mJ energy) for excitation. The longitudinal, shear, and surface acoustic waves generated by a single laser pulse can be time resolved by using a thin-film piezoelectric transducer, and acoustic mode conversions at surfaces are clearly observable. This new photoacoustic material testing technique is useful for fast ultrasonic measurements or for detecting deep subsurface flaws.
10-nm linewidth electron beam lithography on GaAs
Authors: Craighead H. G. , Howard R. E. , Jackel L. D. , Mankiewich P. M.
Published: February 2003

Metal features with 10-nm linewidths were produced on thick GaAs substrates using electron beam lithography. A single layer of polymethylmethacrylate (PMMA) was exposed by an approximately 2-nm-diam electron beam with energies ranging from 20 to 120 keV. Gold-palladium lines less than 20 nm wide, and 15 nm thick, with center-to-center spacings of 70 nm, were produced over 15-μm square fields at all electron beam energies by lift off. The exposure latitude increased significantly for higher electron energies, with 10-nm-wide metal lines formed using a 120-keV writing beam.
Electric field induced heating of high mobility electrons in modulation-doped GaAs-AlGaAs heterostructures
Authors: Shah Jagdeep , Pinczuk A. , Störmer H. L. , Gossard A. C. , Wiegmann W.
Published: February 2003

We report the simultaneous determination of the temperature and mobility of electrons in modulation-doped multiple quantum well GaAs-AlGaAs heterostructures as a function of applied electric field up to 150 V/cm. The decrease of high field mobility with increasing electron temperature is found to be much more rapid than the decrease of the low field mobility with the lattice temperature.
Measurement of virtual crossover in liquid gallium ion source
Authors: Komuro Masanori , Kanayama Toshihiko , Hiroshima Hiroshi , Tanoue Hisao
Published: February 2003

Gallium ion probes of 50 keV obtained from a liquid metal ion source are recorded on silicon and gallium arsenide substrates by using the method of ion bombardment enhanced etching. The minimum linewidth obtained in line exposures is about 20 nm for both substrates which corresponds to the lateral spread of the implanted ions. For a specified value of the lens acceptance half-angle, the line dose varies as a square function of the linewidth, which means that the distribution of the current density in the focused beam is Gaussian. From the theoretical evaluation of the full widths at half-maximum of these distributions, the virtual crossover diameter of the source is estimated to be 40–45 nm independently of the emission current ranging from 4 to 12 μA, and of the value of the needle apex radius of the source in the range 1–3 μm.
Electro-optic effects of (Pb, La)(Zr, Ti)O3 thin films prepared by rf planar magnetron sputtering
Authors: Adachi Hideaki , Kawaguchi Takao , Setsune Kentaro , Ohji Kenzo , Wasa Kiyotaka
Published: February 2003

Epitaxial (Pb, La)(Zr, Ti)O3 thin films were grown successfully on (0001) sapphire substrates at below 600 °C. High quadratic electro-optic coefficient of 0.8×10−16 (m/V)2 was also obtained at 6328 Å. The rf planar magnetron sputtering process improved the quality of the film, which will be suitable for thin-film integrated optic devices.
New oxide growth law and the thermal oxidation of silicon
Authors: Hu S. M.
Published: February 2003

A general kinetic law governing the thermal growth of oxide films is presented. It encompasses the Deal–Grove linear-parabolic growth law and Blanc’s growth law as two special cases; it extends to more general cases where the interface reaction rate has a power-law dependence on oxidant pressure, such as observed in the thermal oxidation of silicon, where neither the Deal–Grove nor the Blanc growth law is applicable. The new growth law is required even for oxidation under atmospheric pressure because of the varying oxidant pressure at the Si–SiO2 interface. Probable mechanisms for silicon oxidation are suggested.
Degenerate four-wave mixing in room-temperature GaAs/GaAlAs multiple quantum well structures
Authors: Miller D. A. B. , Chemla D. S. , Eilenberger D. J. , Smith P. W. , Gossard A. C. , Wiegmann W.
Published: February 2003

We report the first observation of forward degenerate four-wave mixing (DFWM) in room-temperature GaAs/GaAlAs multiple quantum well structures near the exciton resonances. In a sample 1.26 μm thick with sixty-five 96-Å GaAs quantum wells we observe ∼10−4 diffraction efficiency with ∼30 W/cm2 average intensity from a mode-locked laser. We measure nonlinear absorption and DFWM spectra, and also a change in refractive index, per carrier pair/cm3, of neh∼2×10−19 cm3 just below the heavy hole exciton peak. With 20-ns carrier lifetime this corresponds to an effective nonlinear coefficient for cw beams of ‖n2‖≂2×10−4 cm2/W. This is appreciably larger than previous estimates and encouraging for room-temperature all-optical devices.
Vacuum inductive store/pulse compression experiments on a high power accelerator using plasma opening switches
Authors: Meger R. A. , Commisso R. J. , Cooperstein G. , Goldstein Shyke A.
Published: February 2003

The first results of experiments using plasma opening switches for inductive energy storage are described. The switch has been shown to conduct up to 200-kA current for ∼50 ns then to open in <10 ns, transferring the current to an electron beam load. Inductive energy storage, pulse compression, and power multiplication are demonstrated. A simple model explaining the switch operation is presented.
Photoacoustic determination of thin-film thermal properties
Authors: Swimm Randall T.
Published: February 2003

Photoacoustic measurements of the thermal diffusivity and thermal conductivity of a thin-film optical coating are described. The figures of merit characterizing the thin-film/substrate system studied are as follows: ratio of substrate to thin-film effusivity g=5.0%±10%, critical frequency (equal to thin-film thermal diffusivity divided by the square of the thin-film thickness) fc=98 kHz±3%. Measured values of thin-film thermal diffusivity and thermal conductivity are comparable to tabulated bulk values. The ability to directly measure thin-film thermal properties may be particularly valuable in investigating laser damage of optical coatings.
Degradation of 1.3-μm InP/InGaAsP light-emitting diodes with misfit dislocations
Authors: Chin A. K. , Zipfel C. L. , Chin B. H. , DiGiuseppe M. A.
Published: February 2003

The degradation of 1.3-μm InP/InGaAsP light-emitting diodes (LED’s) with misfit dislocations was investigated. Initially, the misfit dislocations were found to be present only in the p-InP confining layer and they thus showed weak (∼1%) contrast in the electroluminescence (EL) image of the light-emitting region. Without bias, no degradation of the LED’s was measured after 103 h at 200 °C. After 103 h at 20 °C and 8 kA/cm2, a previous study found that InP/InGaAsP LED’s containing misfit dislocations did not degrade. However, our study showed that the lifetime of the LED’s varied inversely with the third power of the current density. In the degraded LED’s, the misfit dislocations showed stronger (∼50%) contrast in the EL image, suggesting that they played a significant role in the device degradation. In these devices, misfit dislocations were found not only in the p-InP confining layer but also in the light-emitting region of the active layer. The degradation of InP/InGaAsP LED’s with misfit dislocations is thus consistent with the mechanism of nonradiative recombination enhanced growth of the misfit dislocations into the active layer. For our device structure, wafers with Δa/a≲0.05% lattice mismatch are free of misfit dislocations and thus ensure reliable device operation at high current densities.
Performance characteristics of a low-flow rate 25 mW, LN2 Joule–Thomson refrigerator fabricated by photolithographic means
Authors: Garvey S. , Logan S. , Rowe R. , Little W. A.
Published: February 2003

Using a photolithographic fabrication process microminiature Joule–Thomson refrigerators have been fabricated substantially smaller in size than hitherto and with refrigeration capacities of the order of 25 mW. The devices are 0.5×2×15 mm in size, they operate on nitrogen gas and cool to 88 K in 45 s. The fabrication process allows mass production of the devices at low cost. It was found that the theoretical models used for the design of the refrigerators are adequate at this level of miniaturization.
PtMnSb, a material with very high magneto-optical Kerr effect
Authors: van Engen P. G. , Buschow K. H. J. , Jongebreur R. , Erman M.
Published: February 2003

Results are reported of polar magneto-optical Kerr effect measurements performed at room temperature on the Heusler alloy PtMnSb in the wavelength range 280–2000 nm. The double Kerr rotation has a maximum in excess of 2.5° at 720 nm, which is to our knowledge the highest room-temperature Kerr rotation reported thus far for any material in the wavelength range under consideration. In order to assess the influence of composition the related materials PdMnSb, NiMnSb, and PtMnSn were also investigated. Here the Kerr effect was considerably lower.
Dimensionless analysis of ideal imploding liners
Authors: Gupta R. P. , Kekez M. M. , Lau J. H. , Lougheed G. D.
Published: February 2003

Optimum designing of an imploding liner system consists of matching the liner dimensions and mass to the driver parameters to achieve high-energy density in the final pinch phase. Contours of energy efficiency and dimensionless power at the time of liner collapse have been plotted in the space defined by the Katzenstein dimensionless parameters A and B. These plots are shown to be very useful for studying and designing imploding liner systems.
Evidence for low diffusivity and mobility of minority carriers in highly doped Si and interpretation
Authors: Neugroschel A. , Lindholm F. A.
Published: February 2003

Experimental evidence for low minority-carrier diffusivity and mobility in highly doped Si:As is presented and explained by a simple model. The model emphasizes the carrier transport, including trapping, in the tail states of the minority-carrier band that will influence the minority-carrier mobility and diffusivity while not influencing the majority-carrier transport. The measured values for minority holes in n+-Si:As layers with doping concentrations of about 1.5×1020 cm−3 are Dp≂0.2 cm2/s and μp≂6.3 cm2/Vs, which are about one order of magnitude smaller than the corresponding values for the majority holes. These new results pertain to device design and understanding of heavy doping effects and mechanisms.
Residual double acceptors in bulk GaAs
Authors: Elliott K. R.
Published: February 2003

By using infrared absorption, photoluminescence, and Hall measurements we have observed an additional level associated with a residual acceptor in liquid encapsulated Czochralski GaAs. These results indicate that the defect is a double acceptor with levels 78 and 200 meV above the valence band.
Continuously tunable coherent spectroscopy for the 0.1–1.0-THz region
Authors: Helminger Paul , Messer James K. , De Lucia Frank C.
Published: February 2003

A spectroscopic system is described that provides coherent, continuously tunable coverage from below 100 GHz to above 1 THz. The phase of the microwave power is directly relatable to WWVB and the spectral purity is such that linewidths of less than 0.01 MHz (HWHM) can be observed without apparent broadening. The flexibility and general applicability of this system make possible a wide variety of submillimeter experiments. In order to illustrate the capabilities of this system we report observations of H2O and CO in the region between 300 and 1100 GHz.
Oxidation of silicide thin films: TiSi2
Authors: d’Heurle F. , Irene E. A. , Ting C. Y.
Published: February 2003

The oxidation of TiSi2 thin films on polysilicon illustrates extreme examples of behavior. At 700 °C in wet O2, one observes the formation of titanium oxide and the simultaneous rejection of silicon towards greater depths, away from the oxidized surface layer. At 1100 °C with the same type of sample, one observes the growth of a metal-free layer of SiO2, the formation of which required not only the use of the whole available polysilicon, but the reduction of the initial disilicide to a lower silicide, mostly TiSi. These observations are discussed in terms of previous results obtained either with TiSi2 or with other silicides, and in terms of what is known about the thermodynamics of the system titanium oxide-silicon oxide.
Directional acoustic microscopy for observation of elastic anisotropy
Authors: Hildebrand J. A. , Lam L. K.
Published: February 2003

A directional acoustic microscope is described that has enhanced contrast for elastically anisotropic materials. Directional detection of surface acoustic waves by the acoustic lens is demonstrated on (100) and (111) silicon crystals. The grains of a polycrystalline silicon sample have contrast which varies as a function of lens orientation. Symmetry of contrast variations and measurement of surface wave phase velocity may provide a new way to determine the orientation of microscopic grains.
Photocapacitance of mobile carriers in hydrogenated amorphous silicon solar cells
Authors: Crandall Richard S.
Published: February 2003

Measurements of the capacitance due to photogenerated electrons and holes that are displaced by the electric field are described. A model calculation shows that the photocapacitance is a measure of the drift mobility of the carriers.
Production of large-area single-crystal wafers of cubic SiC for semiconductor devices
Authors: Nishino Shigehiro , Powell J. Anthony , Will Herbert A.
Published: February 2003

A reproducible process is described for growing a thick single-crystal layer of cubic SiC on a single-crystal Si wafer by chemical vapor deposition. A buffer layer, grown in situ, is used between the cubic SiC and the Si substrate to minimize the effect of lattice mismatch. Layers of up to 34 μm thick and several cm2 in area have been grown. Wafers are obtained by chemically removing the Si substrates from the grown layers. Excellent electron channeling patterns produced by these wafers indicate very good crystal quality. Preliminary electrical measurements have yielded electron mobilities up to 380 cm2/Vs.
High quality refractory Josephson tunnel junctions utilizing thin aluminum layers
Authors: Gurvitch M. , Washington M. A. , Huggins H. A.
Published: February 2003

Preparation of high quality all-refractory Josephson tunnel junctions based on Nb/Al-oxide-Nb and Nb/Al-oxide-Al/Nb structures is reported. Critical currents up to 1300 A/cm2 and Vm values up to 35 mV were obtained. The specific capacitance of these junctions is 0.06±0.02 pF/μm2. Junctions were fabricated using standard photolithography and a new plasma etching process coupled with anodization of Nb.
Diffusion of nitrogen in α-Ti
Authors: Anttila A. , Räisänen J. , Keinonen J.
Published: February 2003

The diffusion coefficients of nitrogen in polycrystalline α-Ti have been measured by annealing nitrogen-implanted titanium samples in the low-temperature region, i.e., 450–700 °C. The nitrogen profiles were probed with the ( p,γ) resonance broadening method. The implantation energies were 20–60 keV and the fluences were 1016–1018 ion/cm2, corresponding to 1.4 and 14 at. % at the maximum of the N profile, respectively. The concentration change had only a slight effect on the diffusivity. The irradiation effect on the diffusivity was studied by bombarding the samples with 20–60 keV 22Ne+ ions with 1016–1018 ion/cm2 fluences and 600–keV protons with a 1018 proton/cm2 fluence. However, no significant change was observed.
Laser-controlled etching of chromium-doped 〈100〉 GaAs
Authors: Tisone Gary C. , Johnson A. Wayne
Published: February 2003

The photocontrolled etching of 〈100〉 Cr:GaAs in HNO3 is examined in the wavelength region of 334–514 nm with an Ar ion laser. The etching rate decreases with increasing wavelength and correlates with the optical absorption coefficient in the GaAs. The etching process is found to be photochemically and not thermally controlled. Etch rates for the UV are 30(μ/s)/(MW/cm2) for laser intensities between 3 and 80 kW/cm2.
Formation of an amorphous Rh-Si alloy by interfacial reaction between amorphous Si and crystalline Rh thin films
Authors: Herd S. , Tu K. N. , Ahn K. Y.
Published: February 2003

Interfacial reaction in bilayers of amorphous Si and crystalline Rh thin films has been studied by transmission electron diffraction and microscopy. In a bilayer of ∼190-Å amorphous Si and ∼60-Å polycrystalline Rh films, we have observed the formation of an amorphous Rh-Si alloy film upon thermal annealing at 300 °C. The amorphous alloy film crystallizes into the RhSi phase at 400 °C. On the other hand, no amorphous alloy formation was observed upon annealing a bilayer of ∼150-Å amorphous Si and ∼100-Å polycrystalline Rh films; instead, they react at 300 °C to form Rh2Si, followed by the formation of RhSi or a mixture of RhSi and Rh5Si3 around 400 °C.
Theory of beam-induced currents in semiconductors
Authors: Zook J. David
Published: February 2003

An analytical model is presented for the current flowing in a Schottky diode or shallow p-n junction when the current is generated by an electron beam or light beam. The model represents an exact solution to the three-dimensional diffusion equation when the current-collecting junction is at right angles to a grain boundary or to the semiconductor surface. The finite size of the electron-hole generation region is readily included in the analysis. The results are given in terms of one-dimensional integrals which can simply and accurately be evaluated using a programmable hand calculator. The theory provides a basis for using electron-beam-induced currents or light-beam-induced currents to measure the minority-carrier diffusion length and surface recombination velocity at a grain boundary or surface.
Traps created at the interface between the nitride and the oxide on the nitride by thermal oxidation
Authors: Suzuki Eiichi , Hayashi Yutaka , Ishii Kenichi , Tsuchiya Tatsuo
Published: February 2003

Traps introduced by thermal oxidation of a thin nitride film have been investigated using metal-oxide (top-oxide)-nitride-oxide-semiconductor memory diodes. Memory properties as a function of the initial nitride thickness before thermal oxidation and the top-oxide thickness have revealed that the newly created traps are situated mostly at the top-oxide-nitride interface. The density of the traps is estimated to be (1.6±0.2)×1013/cm2 independent of the initial nitride thickness and the top-oxide thickness.
Direct observation of the principal deep level (EL2) in undoped semi-insulating GaAs
Authors: Brozel M. R. , Grant I. , Ware R. M. , Stirland D. J.
Published: February 2003

A high spatial resolution, near infrared absorption method has been used to determine [EL2] concentrations in semi-insulating undoped Czochralski liquid encapsulated (LEC) GaAs. Fine structure superimposed on the well-known ‘‘W’’ distribution across 〈110〉 diameters of {001} wafers has been detected. Fine structure has also been directly observed in {110} sections of ingots grown along 〈001〉 using a CCTV vidicon system to observe transmitted infrared radiation. The structure consists of narrow bands of increased absorption which correspond with high densities of dislocations in the same specimens.
Use of a superlattice to enhance the interface properties between two bulk heterolayers
Authors: Drummond T. J. , Klem J. , Arnold D. , Fischer R. , Thorne R. E. , Lyons W. G. , Morkoç H.
Published: February 2003

Single interface modulation-doped Alx Ga1−xAs /GaAs heterostructures with the binary on top of ternary were grown by molecular beam epitaxy. By incorporating a 150-Å-thick Alx Ga1−xAs /GaAs three-period superlattice in place of an undoped Alx Ga1−xAs spacer layer, 10-K mobilities of up to 256 000 cm2/Vs were obtained. This value is about 6.5 times that of the previous best value. This dramatic improvement is tentatively attributed to the relief of strain caused by the small but significant lattice mismatch although impurity trapping by the superlattice may also play a role. Normal modulation-doped structures where the ternary is grown on top of binary also showed mobility improvement (about 30%) when the undoped AlGaAs spacer layer is replaced with a three-period superlattice of the same thickness. This concept should have a significant role in heterojunction bipolar transistors, field-effect transistors, lasers, and other heterojunction devices.
Noncontact surface temperature measurement during reactive-ion etching using fluorescent polymer films
Authors: Kolodner Paul , Katzir A. , Hartsough Neal
Published: February 2003

We have used a fluorescence technique to make a noncontact surface-temperature measurement on a thin film of glass resin as it is etched away in a reactive-ion-etching chamber. The glass resin is heavily doped with a fluorescent material whose fluorescence lifetime is temperature dependent. The fluorescence is excited and collected through a remote optical fiber, and the lifetime is measured using a phase-shift technique. The calibration reproducibility of this measurement is about ±1 °C. The fluorescent glass-resin film could be used as an underlayer for monitoring the etching of overlying oxides, photoresists, or patterned metallizations, or a photoresist itself could be doped with the fluorescer. This demonstration opens up the possibility of surface temperature measurement in a wide variety of harsh environments.
High-speed direct single-frequency modulation with large tuning rate and frequency excursion in cleaved-coupled-cavity semiconductor lasers
Authors: Tsang W. T. , Olsson N. A. , Logan R. A.
Published: February 2003

We report a new mechanism of direct frequency modulation, the cavity-mode enhanced frequency modulation (CME-FM), using the newly developed cleaved-coupled-cavity (C3) semiconductor laser. In this operation, one of the diode of the C3 laser was operated as a laser, while the other diode was operated as a frequency modulator. It was shown that a very large frequency excursion of 150 Å and frequency tuning rate of 10 Å/mA have been obtained with a C3 GaInAsP crescent laser operating at 1.3 μm. Time-resolved spectral and spectral-resolved pulse response measurements also showed that such C3 lasers operated in highly stable single-longitudinal mode at all times even under high-speed direct frequency modulation. In addition to the important application as the optical source in FM optical communication systems, the present CME-FM C3 laser can also be used as the optical source in wavelength-division multiplexing systems. Further, it opens the possibility of ultrahigh capacity multilevel optical FM information transmission systems.
On the linewidth enhancement factor α in semiconductor injection lasers
Authors: Vahala K. , Chiu L. C. , Margalit S. , Yariv A.
Published: February 2003

A simple model for the linewidth enhancement factor α and its frequency dependence in semiconductor lasers is presented. Calculations based on this model are in reasonable agreement with experimental results.
Modification of Schottky barriers in silicon by reactive ion etching with NF3
Authors: Ashok S. , Chow T. P. , Baliga B. J.
Published: February 2003

Reactive ion etching of silicon with NF3 gas has been found to alter the silicon surface such that the Schottky barrier height is systematically changed with ion energy. The energetic ions introduce a net positive surface charge which increases the barrier height on  p-Si and decreases it on n-Si. The Schottky barrier modification is found to be a function of ion energy as well as gas plasma used.
Self-interstitial and vacancy contributions to silicon self-diffusion determined from the diffusion of gold in silicon
Authors: Morehead F. , Stolwijk N. A. , Meyberg W. , Gösele U.
Published: February 2003

We present an analysis of gold diffusion profiles in silicon taking into account that both self-interstitials and vacancies are present at thermal equilibrium. We find that at 1000 °C the contribution of self-interstitials to silicon self-diffusion is about equal to that of vacancies.
Heat of crystallization and melting point of amorphous silicon
Authors: Donovan E. P. , Spaepen F. , Turnbull D. , Poate J. M. , Jacobson D. C.
Published: February 2003

Thin layers of amorphous silicon (a-Si) were produced by noble gas ion implantation of (100) substrates held at 77 K. Rutherford backscattering and channeling, and differential scanning calorimetry were used to measure the heat of crystallization, ΔHac, to be 11.9±0.7 kJ/mol, substantially less than the value predicted by scaling ΔHac of a-Ge. The crystal growth velocity is found to have the form v=v0 exp(−2.24 eV/kT). We obtain a new estimate, 1420 K, for the melting temperature of a-Si.
A novel technique for studying electric field effect of carrier emission from a deep level center
Authors: Li G. P. , Wang K. L.
Published: February 2003

A new reverse-bias pulsed deep level transient spectroscopy technique (RDLTS) is reported for studying the electric field effect of carrier emission from a deep level defect. The technique uses a reverse-bias pulse whose duration controls the emission of the carriers from a narrow region. The electric field in the region is determined by the pulse height used. The subsequent transient signal due to the capture of carriers by the defect states in the narrow region, in contrast with the emission signal in conventional DLTS, was obtained. The technique is extremely simple to use and requires no additional equipment when using a conventional DLTS setup. Formulation of this approach and the experimental results using this technique were given to illustrate the validity and simplicity of the technique.
X-ray photoelectron spectroscopy study of hydrogen plasma interactions with a tin oxide surface
Authors: Thomas III J. H.
Published: February 2003

Tin oxide thin films were exposed to an rf excited hydrogen plasma (100 mTorr) for various times. The plasma system was operated in a self-biased mode. X-ray photoelectron spectroscopy analysis of vacuum transferred samples shows that SnO2 is reduced. A thin self-limiting layer of elemental Sn forms on the reduced film to a thickness of ∼10 Å.
An applied voltage to eliminate current transients in a one-dimensional diode
Authors: Lampel Michael , Tiefenback Michael
Published: February 2003

Development of sources for heavy ion fusion motivates study of diode current transients. For the one-dimensional problem a unique applied voltage eliminates transients in the space-charge-dominated case:V(t)=V[4/3 (t/τ)−1/3 (t/τ)4] for t<τ, V(t)=V for t≥τ, where L is diode length, V is steady state diode potential, q/m is charge to mass ratio, and τ=3L(m/2qV)1/2 is a particle transit time through the diode. We derive this result and compare it to computer simulations and experimental results.
Determination of the anisotropic potential at the nematic liquid crystal-to-wall interface
Authors: Yang K. H. , Rosenblatt Charles
Published: February 2003

The integrated birefringence of a surfactant (C16H33NH2)-aligned methoxybenzylidene butylaniline cell as a function of applied magnetic field (up to 100 kG) has been measured. The Oseen and Frank elastic continuum theory and a generalized torque balance equation at the interface have been utilized for the calculation to fit the measured data. A very good fit to the data was obtained using an anisotropic liquid crystal-to-wall interfacial potential of the form C cos2 θ+C4 cos4 θ for the calculation. It was found that C4/C=−0.38.
Plasma etching with surface magnetic field confinement
Authors: Mantei T. D. , Wicker T.
Published: February 2003

A plasma etching reactor is described which combines a primary electron source, surface magnetic field confinement, and independently controlled substrate biasing. Preliminary measurements show that the reactor produces a large volume of dense plasma at low pressure. The plasma parameters are uniform to within ±1% over the working volume, with almost no perturbing radio-frequency electric fields. Profiles can be etched into polysilicon in CF4 plasmas with etch rates ≥2000 Å/min.