bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective black absorbers using rf-sputtered Cr2O3/Cr cermet films
Authors: Fan John C. C. , Spura Steven A.
Published: February 2003

Excellent selective black absorbers for solar radiation, with solar absorptivity of over 0.9 and infrared emissivity of less than 0.1, have been obtained by using rf sputtering to coat metal substrates with a Cr2O3/Cr cermet film, then with a Cr2O3 antireflection coating. By determining the optical constants of Cr2O3/Cr films over the composition range up to 35 vol% Cr, it was found that films containing 29 vol% Cr are nearly optimum for this application. The optical and chemical properties of absorbers made with such films are quite similar to those obtained with electroplated Cr-black coatings. This similarity suggests that the electroplated coatings are actually Cr2O3/Cr cermets comparable in composition and microstructure to the sputtered films.
A highly sensitive magnetic bubble detector in an essentially single-mask overlay
Authors: Verhulst A. G. H. , Bril T. W. , Postma L.
Published: February 2003

A new field-access bubble detector is described and assessed in terms of signal-strength propagation margins and technology benefits. In this design the detection and propagation functions of the detector are separated by means of a sandwich structure. The so-called sandwich detector consists of a thin NiFe layer (detection), an insulation layer of SiO2, and a thick NiFe layer (propagation). The layers are structured with the aid of one mask (no alignment) while two gross masks (alignment accuracy within 25 μm) are used to create the connections to the detection layer. The measured sensitivity of a 35-chevron stretcher sandwich detector, designed for 7-μm bubbles (4π Ms=150 G), is 2 mV/mA.
Isotope separation by resonance scattering
Authors: Bernhardt Anthony F. , Teller Edward
Published: February 2003

The resonant or near-resonant interaction of two atoms or molecules, in states which can respectively emit and absorb photons of nearly the same energy, allows them to scatter with large cross sections compared to the usual van der Waals cross sections. This enhanced scattering can be used to separate a mixture of isotopes in a beam. In most cases, a laser or maser is needed to selectively excite the isotope of interest. For the separation of hydrogen and deuterium, however, a single-step enrichment of nearly 30-fold is calculated at 25% deuterium recovery without the use of lasers or masers.
Optically pumped cell for novel visible decay of inhomogeneous magnetic field or of rf frequency spectrum
Authors: Tam A. C. , Happer W.
Published: February 2003

We have constructed a simple laser-pumped device for a visible and real-time display of an inhomogeneous magnetic field in three dimensions. Photographic records of such displays in the form of constant-field contours spaced 5 mG apart are presented. Our device is capable of high spatial resolution, and we have observed contour lines as sharp as 0.02 cm full width. Such real-time high-resolution contours cannot be obtained by conventional point-by-point mapping. Our device can also be used as an unconventional rf frequency spectrum analyzer.
Semiconductor lasers with integrated interferometric reflectors
Authors: Scifres D. R. , Streifer W. , Burnham R. D.
Published: February 2003

A new integrated interferometric reflector (IIR) is demonstrated in an optically pumped GaAs waveguide laser. It is shown that the laser can be wavelength tuned over 30 Å by very small changes in the refractive index of one IIR branch.
Leaky-mode buried-heterostructure AlGaAs injection lasers
Authors: Kajimura Takashi , Saito Kazutoshi , Shige Noriyuki , Ito Ryoichi
Published: February 2003

Leaky-mode buried-heterostructure injection lasers are fabricated and operated successfully under pulse bias at room temperature. The lasers consist of a thin active layer confined by parallel n- and p-AlxGa1−xAs layers with a high mole fraction of AlAs (x=0.4) and perpendicular p−-AlyGa1−yAs layers with a low mole fraction of AlAs (y=0.25). It is shown that most of the laser power can be coupled out into the low-loss perpendicular layers and emitted from the end facets, resulting in highly collimated beams with a beam divergence of about 1°.
Dependence of maximum trappable field on superconducting Nb3Sn cylinder wall thickness
Authors: Rabinowitz Mario , Arrowsmith H. W. , Dahlgren S. D.
Published: February 2003

Uniform dipole magnetic fields from 1.9 to 22.4 kOe were permanently trapped, with high fidelity to the original field, transversely to the axes of hollow Nb3Sn superconducting cylinders. These cylinders were constructed by helically wrapping multiple layers of superconducting ribbon around a mandrel. This is the highest field yet trapped, the first time trapping has been reported in such helically wound taped cylinders, and the first time the maximum trappable field has been experimentally determined as a function of cylinder wall thickness.
Pinhole imaging of laser-produced thermonuclear alpha particles
Authors: Slivinsky V. W. , Brooks K. M. , Ahlstrom H. G. , Storm E. K. , Kornblum H. N. , Leipelt G. R.
Published: February 2003

We have built a pinhole camera for imaging the deuterium-tritium (DT) burn region of laser-driven implosions by spatially resolving the α particles. Kodak Pathe LR-115 cellulose nitrate film was used as a detector with an 8-mg/cm2 Ta filter. Initial results show that the α particles are produced in a region which is much smaller than the initial glass microsphere.
Quantitative analysis of hydrogen in glow discharge amorphous silicon
Authors: Brodsky M. H. , Frisch M. A. , Ziegler J. F. , Lanford W. A.
Published: February 2003

We report measurements of the hydrogen concentrations and densities of amorphous silicon films prepared from glow discharge plasmas of silane. Quantitative results are obtained from the resonant nuclear reaction 15N+1H→12C+4He+γ by counting the emitted γ rays. Mass spectrographic analysis of the gases evolved upon heating are also used to estimate the relative hydrogen concentrations for different preparation conditions. Comparisons are given to previously reported infrared absorption results and to electron microprobe estimates.
Coherent radiation from a nitrogen laser
Authors: Thomas G. C. , Chakrapani G. , Kerr C. M. L.
Published: February 2003

A spatially coherent oscillator at 337 nm was made by placing a nitrogen discharge inside an unstable resonator of high magnification. An energy of 205 μJ was achieved, with 100 μJ in a diffraction-limited spot. The diffraction-limited coherence could be maintained during amplification to 1.0 mJ in a second discharge.
Direct nuclear pumping of a 3He-Xe laser
Authors: Mansfield C. R. , Bird P. F. , Davis J. F. , Wimett T. F. , Helmick H. H.
Published: February 2003

Lasing of a 3He-Xe laser excited by thermal neutron fluxes has been observed at 2.026, 3.508, and 3.652 μm. The dependence of output wavelength on partial pressure of Xe is presented.
Minority-carrier lifetime reduction in the initial degradation of long-life AlxGa1−xAs-GaAs lasers
Authors: Kato Daisuke
Published: February 2003

The degradation of cw double-heterostructure semiconductor lasers is analyzed. It is clearly shown that the recoverable initial degradation mode of long-life AlxGa1−xAs-GaAs lasers is caused by a reduction of minority-carrier lifetime, the effect of which is readily distinguished from other possible processes such as increased cavity loss or minority-carrier leakage.
Electron tunneling spectroscopy—External doping with organic molecules
Authors: Jaklevic R. C. , Gaerttner M. R.
Published: February 2003

We report the observation of inelastic electron tunneling spectra of molecules introduced into completely fabricated tunnel junctions. By using an external doping method several kinds of molecules have been introduced into Al–Al oxide–Pb diodes yielding strong spectra characteristic of the particular molecules. This technique is a new way of detecting and studying molecules interacting with surfaces. The high sensitivity and greater simplicity of this method increases possible applications of tunneling spectroscopy.
Channeled-substrate planar structure (AlGa)As injection lasers
Authors: Aiki K. , Nakamura M. , Kuroda T. , Umeda J.
Published: February 2003

Undesirable nonlinear ’’kinks’’ in light-output–vs–current characteristics of stripe geometry double-heterostructure (DH) injection lasers are significantly reduced by stabilizing the transverse modes along the junction plane. Built-in passive guiding mechanism is introduced by growing planar (AlGa)As/GaAs DH layers on a grooved GaAs substrate.
Plasma oxidation of aluminum film on GaAs—A study by Auger spectroscopy and transmission electron microscopy
Authors: Chang R. P. H. , Chang C. C. , Sheng T. T.
Published: February 2003

Plasma oxidation of thin polycrystalline aluminum films (∼100 Å) on GaAs has shown that oxidation of aluminum proceeds by an initial rapid grain-boundary oxidation of the aluminum followed by a slower oxidation towards the centers of the individual grains. Continued oxidation results in the growth of Ga-As- oxide layers on both sides of the Al-oxide film indicating that the oxidation of GaAs proceeds by an electric-field-assisted in-migration of oxygen through the Al-oxide layer toward the interface and the out-migration of Ga and As toward the surface. This oxidation process can be used to form an amorphous film of Al-oxide on GaAs. By using the Al-oxide film as a preferential filter for the migration of Ga and As, an amorphous Ga-As-oxide film with a Ga/As concentration ratio of unity all the way to the GaAs substrate can also be achieved.
Broadband generation of tunable Josephson radiation at microwave frequencies
Authors: Varmazis C. , Lukens J. E. , Finnegan T. F.
Published: February 2003

Radiation with an integrated power of about 10−12 W has been obtained from a microbridge Josephson junction. The output can be continuously tuned between 2 and 12 GHz. The frequency and current dependence of radiated power and linewidth are in disagreement with the resistively shunted junction model.
Changes in the upper critical fields and critical currents of Nb3Sn and V3Ga owing to neutron radiation damage
Authors: Snead C. L.
Published: February 2003

Ambient-temperature reactor irradiations of Nb3Sn and V3Ga filamentary superconductors have produced increases in the critical current Ic over a low-fluence regime <∼2×1018 n/cm2 (E≳1.0 MeV) followed by severe reductions of Ic at higher fluences as the critical temperature Tc→0. The low-fluence increases in Ic are attributed to increases in the upper critical field Hc2 with increasing resistivity. In V3Ga, however, because of paramagnetic effects, it appears that the changes in the Ginzburg-Landau upper critical field H*c2(GL) govern the behavior of Ic, and not the measured Hc2 as is the case in Nb3Sn. In order to compare the measured Hc2 of V3Ga with estimates based upon H*c2(GL), spin-orbit scattering must be included in the Maki analysis of Hc2. The spin-orbit scattering does not increase with increasing normal-state resistivity, but rather appears to be decreasing. From the irradiation behavior of Hc2 and H*c2(GL) in V3Ga it is argued that in treatments such as flux-pinning analysis where a reduced field h≡H/Hc2 is used to established scaling laws, it is necessary to use a reduced field h*=H/H*c2(GL) because of the paramagnetic limiting effects.
Series arrays of superconducting-normal-superconducting junctions in the Pb-Sn lamellar eutectic alloy
Authors: Dupart J. M. , Baixeras J.
Published: February 2003

Series arrays of about/100 superconducting-normal-superconducting junctions have been obtained in the oriented Pb-Sn lamellar eutectic alloy. The temperature and normal width dependences of the critical currents flowing through these S-N-S structures have been studied and can be explained in the framework of the Bardeen-Johnson theory for systems in the clean limit.
Aging behavior of radiation-damaged titanium tritide from 3He NMR
Authors: Weaver Harry T.
Published: February 2003

Transient nuclear magnetic resonance (NMR) measurements on 3He, generated by β decay and contained in aging titanium tritide (TiH1.8), have been carried out. The experiments were conducted over a period of about three years during which the rate of helium evolution from the sample abruptly increases. Qualitative analysis of the temperature dependence of the 3He NMR correlates the onset of rapid increase in release rate with the precipitation of large bubbles within the solid. Further consideration suggests these bubbles are preliminary stages for release, since only a small fraction (<10%) of the 3He in TiH1.8 is ever observed in this configuration. This is the first data which directly infers 3He bubbles at the time of release, although blisters have been observed in earlier experiments.
Al2O3 half-wave films for long-life cw lasers
Authors: Ladany I. , Ettenberg M. , Lockwood H. F. , Kressel H.
Published: February 2003

Long-term operating-life data are reported for (AlGa)As cw laser diodes. The use of half-wave Al2O3 facet coatings is shown to eliminate facet erosion, allowing stable diode operation at constant current for periods in excess of 10 000 h.
Efficient harmonic generation from 532 to 266 nm in ADP and KD*P
Authors: Reintjes J. , Eckardt R. C.
Published: February 2003

Second harmonic generation of mode-locked pulses in ADP and KD*P from 532 to 266 nm with 85% conversion is reported. Two-photon absorption coefficients are measured for the two materials and found to be relatively unimportant in the limitation of harmonic conversion compared to the effects of phase mismatch and dispersion.
Sodium passivation in HCl oxide films on Si
Authors: Rohatgi A. , Butler S. R. , Feigl F. J. , Kraner H. W. , Jones K. W.
Published: February 2003

Chlorine has been incorporated into SiO2 films by thermal oxidation of Si in a mixture of O2 and HCl gases. Mobile sodium ions adsorbed on the oxide surface were drifted to the Si-SiO2 interface (0.5 MV cm−1 bias at 200 °C). Passivation, defined as the fraction of mobile sodium charge neutralized, exhibited a pronounced threshold with HCl content in the growth ambient. This was partly due to a similar variation of oxide chlorine content (measured by α-particle backscattering). For fixed growth temperature, passivation was a monotonic function of oxide chlorine content, and was only weakly dependent on the level of sodium contamination over the range 5×1011 to 1×1013 Na/cm2.
Saturation of the junction voltage in stripe-geometry (AlGa)As double-heterostructure junction lasers: A comment
Authors: North D. O. , Sommers H. S.
Published: February 2003

Recently published data concerning a contemporary well-behaved cw stripe-geometry injection laser was accompanied by the assertion that above threshold both the junction voltage and the spontaneous emission exhibit ’’complete saturation’’. This paper shows by detailed analysis of the data that in fact the small incompleteness of the saturation agrees with the value predicted by the new nonlinear theory of injection lasers. The junction voltage, spontaneous emission, and mode powering of this cw laser are interconnected by the theory just as they were in the various types of pulsed lasers already described.
ArF laser enrichment of oxygen isotopes
Authors: Sander R. K. , Loree T. R. , Rockwood S. D. , Freund S. M.
Published: February 2003

Absorption by air in the optical cavity of an ArF discharge laser removes the 16O2 Schumann-Runge lines from the broad lasing output centered at 193 nm. Subsequent irradiation of an oxygen cell induces photochemistry of 17O and 18O, resulting in isotopically enriched ozone.
High-power N2+ laser pumped by charge transfer in a high-pressure pulsed glow discharge
Authors: Rothe D. E. , Tan K. O.
Published: February 2003

Intense laser pulses with peak powers in excess of 0.5 MW have been obtained routinely at 4278 Å [(0, 1) band of B 2Σ+u–X 2Σ+g system] from a unique spark-preionized large-volume TE laser. High-pressure operation of this laser with N2 (3371 Å), Ar (0.912, 0.962, 1.270, 1.791 μ), and Xe (1.723 μ) is also discussed.
1-μs laser pulses from XeF
Authors: Champagne L. F. , Eden J. G. , Harris N. W. , Djeu N. , Searles S. K.
Published: February 2003

Long-pulse operation of the XeF laser has been achieved utilizing electron beam excitation of Ar/Xe/NF3 gas mixtures. For a total mixture pressure of 2.5 atm, ∼0.30 J of 350-nm radiation was obtained in a 1-μs FWHM pulse.
A high-efficiency tunable cw Raman oscillator
Authors: Jain R. K. , Lin Chinlon , Stolen R. H. , Pleibel W. , Kaiser P.
Published: February 2003

Continuously tunable cw Raman oscillation has been achieved in the visible by pumping a single-mode fused silica fiber with several lines from an argon ion laser. The 100-m-long fiber has a core diameter of 3.3 μm and a loss of 17 dB/km at 5145 Å. Threshold was achieved with ∼1.0 W of pump power in the fiber. With 4 W of 5145-Å power coupled into the fiber, the Raman oscillator was prism tuned over 80 Å. Typical linewidths were ∼2 Å. At 5280 Å, net input to output power conversion efficiencies of ∼9% and pump depletion of over 80% have been achieved. The simplicity, efficiency, and broadband tunability of fiber Raman oscillators both in the visible and in the near infrared make them potential rivals to other coherent sources of tunable radiation, such as dye lasers and parametric oscillators.
Generation of single synchronizable picosecond 1.06-μm pulses
Authors: Tomov I. V. , Fedosejevs R. , Richardson M. C.
Published: February 2003

We report the generation of reliable synchronizable single mode-locked l.06-μm pulses with pulsewidths variable from 1.3 ns to the spectral transform limit of 15 ps.
Richardson constant of Al- and Au-GaAs Schottky barrier diodes
Authors: Borrego J. M. , Gutmann R. J. , Ashok S.
Published: February 2003

The Richardson constant of Al- and Au-nGaAs Schottky barrier diodes of low doping concentration has been determined from the measured forward I-V characteristics. Richardson constants higher than the theoretical are related to the presence of an additional majority-carrier current caused by recombination of electrons at traps at the metal-semiconductor interface. The data shows that the traps are located approximately 0.75 eV below the conduction band and are in equilibrium with the metal.
Drift-field Schottky-barrier solar-cell calculations
Authors: Castañer Muñoz L. , Ferrarons C.
Published: February 2003

The spectral response of a Schottky-barrier solar cell incorporating an inhomogeneous impurity doping profile is numerically simulated. The total short-circuit current is calculated as a function of the electric field intensity for the cases of front and back illumination. The effect of the semiconductor depth and barrier height are simulated.
Atomic indium photodissociation laser at 451 nm
Authors: Burnham R.
Published: February 2003

Stimulated emission has been obtained on the 451-nm line in neutral atomic indium through photodissociation of indium monoiodide vapor using argon fluoride laser radiation at 193 nm. Laser pulses with energies of 0.5 mJ resulted from the absorption of 30 mJ of ArF laser radiation.
Angular distribution of laser light scattered from laser-produced plasma at high irradiance
Authors: Ripin B. H.
Published: February 2003

Angular distributions of scattered laser light from Nd-laser-produced plasma at irradiances of 1015–1016 W/cm2 were measured. Total reflectivities in the range 20–50% are found. The total reflectivity remains approximately constant as the target is rotated from normal incidence up to 50°–60°, implying the existence of a steep density gradient near the critical density and/or absorption of laser light in the underdense region of the plasma.
Investigation of ion-implantation damage with x-ray double reflection
Authors: Lecrosnier D. P. , Pelous G. P. , Burgeat J.
Published: February 2003

The lattice parameters of boron-implanted silicon layers have been measured by an x-ray diffraction technique. The rocking curves show an expansion volume which anneals in several stages: 100, 280, and 400–600 °C. Around 600 °C, an almost stress-free crystal is found. This result suggests the formation of defect complexes having a compensating effect on the crystal lattice.
A capacitively shunted superconducting microbridge
Authors: Chiao R. Y. , Levinsen M. T.
Published: February 2003

A superconducting microbridge small enough to exhibit the Josephson effect has been shunted by a large external capacitance. Surprisingly little capacitive hysteresis is observed in its I-V characteristic. Prominent subgap structures are seen. The resistively shunted junction (RSJ) model fails to explain the observations.
Transferred-electron effects in n-GaAs under hydrostatic pressure
Authors: Czubatyj W. , Shaw M. P.
Published: February 2003

Experimental results show that the peak velocity, peak electric field, and saturated velocity of the velocity–electric-field curve for n-GaAs all increase substantially with increasing hydrostatic pressure up to about 10 kbar; the peak velocity and field then begin decreasing with further increase in pressure. The extraction of the data from the current-voltage characteristics is based on an exploitation of the influence of the boundary conditions on the manifestation of transferred-electron-induced (Gunn) current instabilities.
Nuclear-orientation techniques for achieving directed radiations from grasers
Authors: Wilson G. V. H.
Published: February 2003

The advantages of exploiting the anisotropic γ radiations from oriented nuclei in the development of grasers are pointed out. Nuclear orientation may be achieved by either static or dynamic means. Some simple techniques for switching the direction of nuclear polarization and hence of the radiation emission are summarized.
Nonlinear optical response of metal-barrier-metal junctions
Authors: Fan B. , Faris S. M. , Gustafson T. K. , Bridges T. J.
Published: February 2003

The time-averaged current induced by incident radiation across electronic tunneling junctions is shown experimentally and theoretically to have a highly nonlinear dependence on the field intensity for a range of tunneling barrier thickness.
Isotope enrichment in sputter deposits
Authors: Wehner G. K.
Published: February 2003

The isotope ratio in metal deposits obtained by sputtering a flat target at low ion energy (100 eV) under normal ion incidence is a function of the ejection angle. The lighter isotope (s) are enriched in the direction normal to the target surface as result of ’’reflective collisions’’ which occur when an atom collides with one of heavier mass underneath. Experimental results are presented for Cu(63-65) and the seven Mo isotopes.
A protuberant shock wave driven by laser-produced fast ions
Authors: Azechi H. , Sakagami Y. , Yamanaka T. , Yamanaka C.
Published: February 2003

In ambient atmosphere, a protuberant shock wave driven by laser-produced fast ions was observed by time-resolved photographs with 5-μm and 30-psec resolutions. This protuberant shock wave appeared only when the incident laser intensity exceeded 5×1013 W/cm2. At this intensity, the fast ions were observed using the charge collectors.
Aerosol sizing by means of laser-induced fluorescence
Authors: dos Santos R. , Stevenson W. H.
Published: February 2003

A technique for accurately measuring in situ the size distribution of liquid aerosols is described. The method is based on the measurement of signal modulation when fluorescent particles cross the probe volume of a real fringe laser velocimeter. This provides an exact measurement of droplet diameter free from the errors associated with a similar scattered light technique.
Hot-electron diffusion noise in n-silicon using a radiometric method in the X-band region
Authors: Zimmermann J. , Bonfils S. , Leroy Y. , Constant E.
Published: February 2003

A radiometric method for the measurement of the diffusion noise in homogeneous semiconductors is presented. The work has been carried out on epitaxies silicon n+n n+ at room temperature, the electric field applied (1⩽E⩽70 kV/cm) being along the 〈111〉 direction. The results are in close agreement with those computed through the impedance field method with the high field diffusion coefficient values obtained by Canali who had used the time-of-flight technique.
The electrical properties of stacking faults and precipitates in heat-treated dislocation-free Czochralski silicon
Authors: Kimerling L. C. , Leamy H. J. , Patel J. R.
Published: February 2003

We have studied the electrical properties of dislocations, stacking faults, and precipitates produced during 1200 °C aging of crucible-grown silicon. The defects were examined by SEM in the charge collection mode, at temperatures from 77 to 300 °K. Undecorated Frank extrinsic stacking faults exhibit defect energy levels in the upper half of the gap (∼Ec−0.1 eV). The partial dislocations bounding these faults possess energy levels lower than Ec−0.3 eV. Finally, precipitates are observed to act as microplasma sites at low (T<300 °K) temperatures.
Gaussian beam stabilization in a long absorptive plasma column
Authors: Yuen S. Y.
Published: February 2003

The behavior of a Gaussian laser beam propagating in a long absorptive plasma column is studied theoretically. The plasma is represented by a complex refractive index which varies quadratically with transverse position. With an absorption loss which is minimum at the axis, the width of the Gaussian beam will converge at large propagational distance to a constant which depends on the plasma characteristics alone. It is found that stable propagation of a Gaussian beam is obtained without requiring that the transverse variation of the real part of the refractive index be favorable to beam trapping.
Scanning ESCA: A new dimension for electron spectroscopy
Authors: Hovland C. T.
Published: February 2003

Experiments have been conducted to determine the feasibility of the theoretical experiment set forth by Cazaux. The experiment consists of electron bombarding a thin foil of aluminum with a thin specimen mounted on the opposite side. A focused scanning electron beam is used to bombard the aluminum substrate to produce a localized source of AlKα x rays. This focused Al x-ray (hν=1.4 keV) source creates a spatially localized source of photoelectrons in the specimen. The photoelectrons are separated in energy with a cylindrical mirror spectrometer to produce an ESCA spectrum from an area of less than 20 μm in diameter. Two-dimensional ESCA images have been obtained by this method utilizing intensity variations in the amplitude of a selected photoelectron peak to intensity modulate a cathode ray tube monitor as the electron beam is scanned.
Electric-field-induced optical rectification in nitrobenzene
Authors: Ward J. F. , Guha J. K.
Published: February 2003

The first observation of dc-electric-field-induced$optical rectification is eported. In this process a dc polarization is produced in a medium (in this case nitrobenzene) by the simultaneous presence of dc and optical electric fields. The relation between this process and the Kerr effect is found to be consistent with that predicted by permutation symmetry. A bolometerlike response also seen in these experiments is discussed.
XeF* (C1/2) radiative lifetime measurement
Authors: Eden J. Gary , Searles Stuart K.
Published: February 2003

By monitoring the spontaneous emission from electron-beam-excited xenon difluoride (XeF2) plasmas, the radiative lifetime of XeF* [C (1/2)] has been determined. Excited XeF was formed directly through electron-impact dissociative excitation of XeF2. The time behavior of the subsequent 351-nm fluorescence displayed two distinct exponential decay regions. The first was characterized by a pressure-independent decay constant of 16.5±5 ns, the radiative lifetime of XeF* [C (1/2)]. The time constant of the second region was linearly dependent on XeF2 pressure, indicating that C-state XeF molecules are, in the late afterglow, formed by a two-body collision process exhibiting a large rate constant (∼3×10−10 cm3 sec−1).
Growth of GaAs-Ga1−xAlxAs over preferentially etched channels by molecular beam epitaxy: A technique for two-dimensional thin-film definition
Authors: Tsang W. T. , Cho A. Y.
Published: February 2003

In this paper, studies of the molecular beam epitaxy (MBE) of GaAs-Ga1−xAlxAs multilayer structures over preferentially etched channels on GaAs substrates are described. It is found that the growth characteristics with MBE are entirely different from those obtained from similar experiments when LPE is used. Results obtained indicate that this etch-and-fill technique using MBE as the growth process should be particularly useful in fabricating injection lasers, laser arrays, and integrated optics components which require planar definition.
Enhanced degradation and deep-level formation at dislocations in GaAs0.6P0.4 LED’s
Authors: Metz S.
Published: February 2003

Spatially resolved measurements of the red (1.9 eV) and infrared (1.27 eV) luminescence, resulting from near-edge and deep-level recombinations, respectively, are presented. The samples are excited by current injection at 300 K and measured before and after a period of stressed operation. An enhanced degradation is observed at distinct lines running parallel to 〈110〉 directions which is combined just there with an increasing density of the deep-level recombination centers.
20-MHz acoustic waves from pulsed thermoelastic expansions of constrained surfaces
Authors: von Gutfeld R. J. , Melcher R. L.
Published: February 2003

Repetitive pulses from lasers with pulse widths 5–10 nsec or a current generator with 10–25-nsec widths have been used to launch acoustic waves by thermoelastic expansions. For the laser case, when transparent media such as quartz plates are used to acoustically constrain the energy absorbing surface, an increase of up to 46 dB at 20 MHz was observed over that generated from a free surface. An experiment using a scannable laser to generate elastic waves for flaw detection in a metallic sample is described.
Direct measurement of broad spectral electromagnetic wave energy generated by an intense relativstic electron beam
Authors: Efthimion P. C. , Schlesinger S. P.
Published: February 2003

A direct determination is made of the total power radiated in a single pulse, ℱ P (ω)  dω, by an intense relativistic electron beam cyclotron maser configuration as a function of applied magnetic field. The existence of other possible instabilities over a broad spectral range notwithstanding, the total output is dominated by the maser instability occurring at the relativistic cyclotron resonance magnetic field. The results for two different anode-cathode spacings, corresponding qualitatively to cold and warm beam conditions, are presented and compared. A possible explanation accounting for the existence of high power noise radiation at low magnetic fields for the warm beam case is discussed.
X-ray and γ-ray emission from channeled relativistic electrons and positrons
Authors: Terhune R. W. , Pantell R. H.
Published: February 2003

The characteristics of the radiation from channeled relativistic electrons and positrons are discussed and model calculations carried out. Radiation near 2.5 keV associated with transitions etween the 2 p→1s eigenstates of 2-MeV electrons channeled along the 〈110〉 axis of MgO is predicted with 50 times the usual bremsstrahlung intensity in a 10% bandwidth. Recent low-energy bremsstrahlung measurements made with 28-MeV electrons propagating along an axis in silicon are interpreted in terms of this model.
Ion-implanted silicon profiles in GaAs
Authors: Lee D. H. , Malbon R. M.
Published: February 2003

Depth distribution profiles of silicon impurities implanted at 50 to 500 keV have been measured by secondary-ion mass spectrometry. The as-implanted profiles are approximately Gaussian with agreement between experiment and theory better than 10% for the projected ranges Rp and within 20% for the standard deviations ΔRp. Negligible diffusion of a 400-keV implanted silicon profile is observed after a 800 °C 20-min anneal in a flowing hydrogen/arsenic atmosphere without dielectric encapsulation.
Spectroscopic studies in the picosecond domain with synchronously mode-locked dye lasers
Authors: Royt T. R. , Lee Chi H.
Published: February 2003

Synchronous mode locking of two dye lasers was employed to obtain pairs of independently tunable picosecond pulses that were precisely synchronized in time. Overlapped pulses in strontium vapor were used to generate tunable picosecond pulses in the vacuum uv. The tunability was employed to study resonant enhancement of a four-wave parametric process by the 4d6p autoionizing resonance. Mutually separated pulses were employed to measure the build-up and decay of coherence for a two-quantum excited state. The decay was found to be faster than theoretical predictions that assume only velocity dephasing.
Experiment with a cw N2O gasdynamic laser and its qualitative comparison with a CO2 laser
Authors: Milewski J. , Brunné M. , Irczuk M. , Stańco J. , Zieliński A. , Rabczuk G. , Demin A. I. , Kudriavtsev E. M. , Volkov A. Yu. , Sobolev N. N.
Published: February 2003

Preliminary experimental data concerning an N2O/N2 thermally excited and selectively pumped mixing cw gasdynamic laser are reported and compared with those concerning a CO2/N2 laser operating at similar conditions.
A tunable visible and ultraviolet laser on S2 (B3Σu−–X3Σg−)
Authors: Leone Stephen R. , Kosnik Kenneth G.
Published: February 2003

Laser action has been achieved on the B3Σu−–X3Σg− transition of S2 by optical pumping with a frequency-doubled dye laser and a nitrogen laser. The observed lasing is line tunable from 365 to 570 nm. The S2 molecule is a promising candidate for an efficient scalable ultraviolet laser system.
Reduction of the effective height of metal–n-InP Schottky barriers using thin epitaxial layers
Authors: White P. M. , Brookbanks D. M.
Published: February 2003

Reduction of the effective height of metal–n-InP Schottky barriers from 0.4 to 0.24 eV has been achieved by utilizing thin epitaxial n+ surface layers which are fully depleted at zero bias. A novel ’’ramp-etching’’ technique has been used to investigate the effect of n+ thickness on current-voltage characteristics and shows that further effective reductions are possible using thicker n+ layers which are not depleted at zero bias. Low height barriers of this type have applications in high-efficiency transferred electron microwave oscillators.
Light sensitivity enhancement of image intensifiers
Authors: Dir G. A. , Haas W. E. L. , Adams J. E.
Published: February 2003

It was observed that liquid-crystal–photoconductor reflective light intensifiers, without optical blocking layers, become more sensitive to the imaging light when the irradiance of the actinic read-out light is increased. Measurements illustrating the effect and an interpretation are presented.
Pressure dependence of electron temperature using rf-floated electrostatic probes in rf plasmas
Authors: Cantin A. , Gagné R. R. J.
Published: February 2003

A new technique, which eliminates ac between probe and plasma by means of a ’’follower’’, permits electrostatic probes to be used in rf plasmas with a degree of confidence and accuracy which is equal, if not better, to that for a dc discharge. Measurements in argon, using this technique, have shown that electron temperature (Te) in an rf discharge is not higher than in dc discharge. Moreover the values of Te do not agree with von Engel’s law, but are in close agreement with a theory based on free diffusion and extrapolated up to values of pR=20 Torr cm (pressure times tube radius). These results are in contradiction with published electrostatic probe results for a positive column, but agree with published results as determined by microwave radiometry and optical spectroscopy. The hypothesis is made that the supporting evidence in favor of von Engel’s law, afforded by published electrostatic probe results, could be due to an artifact.
Dose dependence of residual lattice disorder in ion-implanted and annealed silicon
Authors: Christodoulides C. E. , Grant W. A. , Williams J. S.
Published: February 2003

Significant nonlinear effects have been observed in the dose/disorder relationship for Pb-implanted Si both before and after annealing. The results suggest that accumulated stresses within the implanted Si layer may play a significant role in recrystallization.
Surface energy and the theory of the friction of solids
Authors: Finkin Eugene F.
Published: February 2003

An analysis shows that surface energy may be the dominant parameter in the theory of solid friction through its influence on the real area of contact. This view is compatible with current adhesion and deformation theories of friction.
A controlled-atmosphere electron-microscopy study of the influence of oxygen on the interdiffusion of gold and iron
Authors: Cairns J. A. , Keep C. W. , Waite R. J. , Ziegler J. F. , Tu K. N.
Published: February 2003

Controlled-atmosphere electron microscopy is used to show that when thin (∼150 Å) superimposed layers of Au/Fe/Au are heated in an oxygen environment, a dramatic breakup of the gold into islets occurs at 300–350 °C. By utilizing previous Rutherford backscattering observations of this system and complementing the electron-microscope observations with x-ray photoelectron spectroscopy examination, it is possible to gain an insight into the nature of the process and highlight the role played by oxygen in the breakup of the gold layer.
Refractive index of garnet films containing Ca and Ge
Authors: Wöhlecke Manfred , Suits James C.
Published: February 2003

Refractive-index–vs–wavelength data are reported over a wavelength range of 0.56 to 0.97 μ for several garnets containing Ca2+ and Ge4+ and various compositions of rare-earth ions. The experimental data were fitted to a two-term Sellmeier expression and a linear relation between index of refraction and number of Fe3+ ions was found for garnet composition with small rare-earth content.
Comparison of range and range straggling of implanted 10B and 11B in silicon
Authors: Ryssel H. , Kranz H. , Müller K. , Henkelmann R. A. , Biersack J.
Published: February 2003

In this paper the ranges of implanted boron ions in silicon measured by the 10B (n,α)7Li reaction and by means of Hall-effect and sheet-resistivity measurements are compared for 10B and 11B. It is shown that the ranges and the range straggling are identical within the experimental error.
Addition of HCl to the double-pulse copper chloride laser
Authors: Vetter A. A. , Nerheim N. M.
Published: February 2003

Addition of small amounts of hydrogen chloride to the buffer gas of a double-pulse CuCl laser causes an increase in the production of copper atoms in the ground state. A maximum laser energy increase of 15% was observed and the span of delay times for which laser action occurred increased.
Efficient injection mechanism for electroluminescence in GaN
Authors: Jacob G. , Bois D.
Published: February 2003

GaN electroluminescent devices have been realized with external quantum efficiency close to 1% in the yellow and 0.3% in the green. The active region is composed of two zinc-doped layers, n type and semi-insulating (1000 Å), and a metal contact. Electroluminescence is obtained with voltages of 5–10 V typically and values as low as 2.5 to 4 V have been obtained (+ on the metal). A model is proposed to explain the injection in this structure; it involves impurity band conduction and electron injection from the (n) to (i) side. The I (V) characteristic is found to follow the Frenkel-Poole law.
Coherent anti-Stokes Raman scattering in a hollow dielectric waveguide
Authors: Miles R. B. , Laufer G. , Bjorklund G. C.
Published: February 2003

Hollow waveguides are shown to enhance coherent anti-Stokes Raman scattering by two to three orders of magnitude for low-pressure gases. Theoretical and experimental comparisons of signals generated by tight focusing in a cell with those generated in a hollow waveguide are preented. These arguments show that maximum conversion in the hollow waveguide occurs at pressures on the order of several atmospheres compared to greater than 50 atm for tight focusing, and for low pressures enhancements are on the order of the square ofthe waveguide length to confocal beam parameter ratio.
The origin of dislocation climb during laser operation
Authors: O’Hara S. , Hutchinson P. W. , Dobson P. S.
Published: February 2003

The origin of the dislocation climb which takes place in the presence of electron-hole recombination in laser structuresis discussed. TEM studies on lasers which have been degraded by either forward bias or by optical pumping show that the climb dipoles are extrinsic in both cases. In addition, completely isolated interstitial loops can form which also have the characteristic climb appearance of the larger dipoles. Existing theories for the origin of the interstitials required to account for the observed climb are considered in detail, and it is concluded that the climb structures can best be explained by the emission of both gallium and arsenic vacancies from the dislocation as a consequence of nonradiative processes occurring at the dislocation core.
Diffusion lengths in solar cells from short-circuit current measurements
Authors: Stokes E. D. , Chu T. L.
Published: February 2003

The minority-carrier diffusion length in the base region of a silicon solar cell has been determined by measuring the short-circuit current as a function of the wavelength of incident light. The incident light intensity required to produce a given short-circuit current is a linear function of the reciprical absorption coefficient for each wavelength, and the extrapolation of this linear relation to zero intensity yields the diffusion length. This method is similar to the surface photovoltage and open-circuit voltage methods; however, the accuracy for high light bias levels appears to be greatly improved.
Two- and three-body quenching of XeF* by Ar and Xe
Authors: Rokni M. , Jacob J. H. , Mangano J. A. , Brochu R.
Published: February 2003

In this paper we report two- and three-body quenching of the XeF* (B2Σ+1/2) state by Ar and Xe. The rate constants were obtained by analyzing the dependence of (B2Σ+1/2 →X2Σ+1/2) radiation on the partial pressures of Ar, Xe, and F2. The XeF* was produced by a high-energy e-beam. We have determined the two- and three-body quenching rates by Ar to be 8±4×10−13 cm3/sec and 1.5±0.5×10−32 cm6/sec. Xe quenches XeF* with a three-body rate constant of 3±1.5 ×10−31 cm6/sec; the third body was mainly argon.
New method for the determination of luminescence lifetimes by using the beat noise of a cw laser as a multifrequency-modulated source
Authors: Hieftje G. M. , Haugen G. R. , Ramsey J. M.
Published: February 2003

The excitation of a fluorophore by rapidly varying fluctuations in a free-running argon-ion laser is shown to produce variations in measured fluorescence. The power spectrum of the fluctuations can yield lifetime information on luminescence and the experimental apparatus described exploits this phenomenon. Methods of improving the measurements are also considered.
Momentum transfer to target from laser-produced plasma
Authors: Kuriki K. , Kitora Y.
Published: February 2003

The impact transferred from laser-produced plasma to target was measured, and the formed plasma was studied by schlieren and shadow photographs. The cylindrical detonation wave theory was in general agreement with the plasma features in the early energy deposition phase but failed to predict the momentum transfer from plasma to target. The momentum transfer agreed with the theory of spherical blast wave which follows the cylindrical detonation wave.
Far-infrared detection using photoconductivity of negative donor ion states in silicon
Authors: Norton P. , Slusher R. E. , Sturge M. D.
Published: February 2003

Far-infrared detection using the bulk photoconductivity associated with negative donor ion states in silicon is found to provide nanosecond response times and quantum efficiencies of a few percent. It is estimated that this detector can be used in a heterodyne receiver with NEP’s in the range from 10−16 to 10−19 W/Hz in the wavelength range from 100 to 500 μm.
Parametric focusing of intense ion beams
Authors: Mahaffey R. A. , Marsh S. J. , Golden J. , Kapetanakos C. A.
Published: February 2003

Focusing of charge- and current-neutralized intense ion beams is accomplished by propagating the beam along a spatially periodic axial magnetic field. This focusing results in local variations in the beam radius and density. At one location, the measured particle density is enhanced over the emitted density by at least a factor of 4. Current density enhancements in excess of an order of magnitude using this method should be obtainable.
Finite-bandwidth control of fast electrons produced by parametric instability
Authors: Obenschain S. P. , Luhmann N. C.
Published: February 2003

In a microwave experiment simulating laser-plasma interactions, the production of fast electrons by the parametric decay instability is found to be significantly decreased by replacing a monochromatic pump with a noisy one. With this experimental arrangement, it is observed that finite bandwidth also inhibits the formation of density cavitons.
Hollow-cathode aluminum ion laser
Authors: Gerstenberger D. C. , Reid R. D. , Collins G. J.
Published: February 2003

We have observed five laser transitions in the 358–747-nm region, all of which originate from excited energy levels of singly ionized aluminum. Laser action was obtained by exciting a neon buffer gas in an aluminum hollow cathode and the excitation mechanism is thought to be a Ne+-Al charge transfer reaction. Single-line output power on the 358-nm laser transition of Al II was 9 mW, while multiline infrared output was 5 mW.
Observation of confined propagation in Bragg waveguides
Authors: Cho A. Y. , Yariv A. , Yeh P.
Published: February 2003

A new type of waveguiding in a slab dielectric bounded on one side by air and on the other by a periodic layered medium (grown by molecular beam epitaxy) has been demonstrated.
Variations in the transition probabilities and quantum efficiency of Nd3+ ions in ED-2 laser glass
Authors: Brecher C. , Riseberg L. A. , Weber M. J.
Published: February 2003

Radiative and nonradiative transition probabilities from the 4F3/2 state of Nd3+ in ED-2 laser glass were measured for ions in different sites using laser-induced fluorescence line-narrowing techniques. Both radiative and multiphonon transition probabilities were found to be site dependent, with the relative radiative quantum efficiency varying by as much as 50%.
Poling rates for films of polyvinylidene fluoride
Authors: Blevin W. R.
Published: February 2003

The growth of the pyroelectric coefficient p (T) of 6-μm films of polyvinylidene fluoride during poling with a field of 100 MV m−1 was measured for the poling temperatures Tp=100, 80, 60, 40, and 20 °C. Decreasing Tp greatly reduced the growth rate of p (T), but not the value of p (T) attainable by prolonged poling. For the best poled films p (T) increased with the film temperature T from 30 μC m−2 K−1 at 0 °C to 55 μC m−2 K−1 at 80 °C. The poling period required for p (20 °C), the room-temperature value of p (T), to reach 25 μC m−2 K−1 ranged from 0.5 min at Tp=100 °C to 8000 min at Tp=20 °C.
Photoelectronic properties of CdTe-electrolyte heterojunctions: Feasibility as solar energy converters
Authors: Menezes Cornelius , Sánchez-Sinencio F. , Helman J. S. , Williams Richard , Dresner J.
Published: February 2003

We show that cadmium telluride is a promising material for semiconductor-electrolyte solar cells. Polycrystalline n-type CdTe, in contact with an aqueous solution of SnCl2, forms a well-defined Schottky barrier. The efficiency in sunlight is 4.8%. The cell shows a drift of characteristics with time that may be associated with a low rate of formation of hydroxide on the surface. However, operating stability is relatively good compared with other semiconductor-electrolyte cells that have been reported in the past.
I-V impurity profiling with a Schottky barrier
Authors: Shannon J. M.
Published: February 2003

A method is described for determining the impurity profile beneath silicon Schottky diodes at room temperature when current transport is dominated by thermionic-field emission of electrons. The technique may be used when depleting between 1012 and 1013 charges cm−2.