bluuebunny/crossref_metadata_2025 huggingface dataset:
An rf bridge technique for contactless measurement of the carrier lifetime in silicon wafers
Authors: Tiedje T. , Haberman J. I. , Francis R. W. , Ghosh A. K.
Published: February 2003

A contactless rf technique has been developed for measurement of the photoconductivity induced in silicon wafers by a flash of light from GaAs laser diodes. The carrier lifetime inferred from the photoconductivity decay correlates well with diffusion length measurements made on solar cells fabricated from the same wafers. The technique has been applied successfully to silicon whose resistivity is as low as 0.1 Ω cm and lifetime as short as 0.2 μs.
Coherence effects in synchronously pumped mode-locked dye lasers
Authors: Casperson Lee W.
Published: February 2003

A formalism is developed for describing the evolution of picosecond mode-locked pulses in synchronously pumped dye lasers. The finite phase memory of the molecular wave functions is included, and it is found that the resultant coherence effects can be dominant for operation close to exact synchrony. Considerations of the isotropic molecular orientational distribution and the finite vibrational relaxation times are also essential in obtaining quantitative agreement with experimental results.
Bubble growth in laser irradiated glass
Authors: Hastings D. E.
Published: February 2003

We have considered the problem of the growth of a bubble from a preexisting nucleation site in laser irradiated glass. We show that thermal expansion of gases inside the bubble will not give significant growth. For glass temperatures below the vaporization temperature we show that a bubble can grow by CO2 diffusion for glasses with a soda content. For glass temperatures above the vaporization temperature we examine the growth of vapor bubbles. We conclude that bubbles of several microns in size can be obtained in laser irradiated glass.
Applied-B field ion diode studies at 3.5 TW
Authors: Johnson D. J. , Dreike P. L. , Slutz S. A. , Leeper R. J. , Burns E. J. T. , Freeman J. R. , Mehlhorn T. A. , Quintenz J. P.
Published: February 2003

The performance of 7 and 14 cm radius, applied B-field, focusing ion diodes is investigated on the Proto II accelerator at a diode power of 3.5 TW. The ion production efficiency of the 14-cm diode is determined to be approximately 80% for the 30-ns power pulse used. When a 2 Torr air background gas was used in the beam propagation region between the diode and the target, the ion beam was observed to be approximately 70% magnetically neutralized in regions of approximately 20 kG transverse B-field and ≥95% in regions of no B-field. The local and global divergence of the 1.4-MV beam were each determined to be approximately 1°. Local source power brightness of >1.5×1013 W/cm2/rad2 is inferred.
Two-dimensional plasma model for the arc-driven rail gun
Authors: Powell John D. , Batteh Jad H.
Published: February 2003

A previously developed one-dimensional model for studying the fluid-mechanical electrodynamical properties of the plasma in an arc-driven rail gun is extended to two dimensions. The analysis includes deriving a set of general, time-dependent equations, the solution of which yields the associated properties of the arc. These equations are then solved under the assumptions that the flow variables are steady in a frame of reference which accelerates with the arc, and that the effect of the arc’s acceleration upon these variables can be neglected. Numerical calculations are carried out to analyze arcs in recent experiments. In addition to the numerical calculations, some approximate analytic solutions, which are applicable under certain limiting conditions, are also worked out. These limiting-case solutions are then used to derive a set of scaling relations which indicate how the arc properties vary with gun size, projectile mass, and acceleration characteristics. Considerable discussion of the assumptions and the results is given emphasizing particularly the physical reasons for the differences with previous one-dimensional calculations.
Current density for cold cathode discharge gap in rare gases
Authors: Lagushenko R. , Maya J.
Published: February 2003

We report experimental current density results for tungsten and yttrium cold cathode discharge gap ( j, ac, and dc) as a function of pressure (PRG) for He, Ne, Ar, and (99.9%Ne+0.1% Ar) at 100–220 V. We calculated the discharge gap parameters both for ac and dc cases and compared them to experimental results. Conclusions drawn from this comparison are discussed.
An optical emission study of the glow-discharge deposition of hydrogenated amorphous silicon from argon-silane mixtures
Authors: Kampas F. J.
Published: February 2003

Optical emission intensities from atomic silicon and argon and molecular hydrogen have been measured in silane-argon mixture glow discharges as a function of silane percentage and rf voltage. These measurements show that the electron concentration decreases and the average electron energy increases as the silane concentration increases. This dependence explains why the deposition rate of hydrogenated amorphous silicon from silane-noble gas mixtures is not proportional to the silane concentration.
Ion implantation damage and annealing in germanium
Authors: Holland O. W. , Appleton B. R. , Narayan J.
Published: February 2003

We have observed a unique damage structure, which forms within the amorphous phase, in ion-implanted Ge above a certain ion dose. This structure, which represents a drastic alteration of the near-surface morphology, is responsible for the adsorption of large quantities of C and O onto the surface of the implanted area. Results are presented of a systematic study of this effect and possible mechanisms for its information are discussed. Ion implantation conditions desirable for device applications are established and deleterious effects due to the presence of this damage upon both solid- and liquid-phase epitaxial growth of the implanted layers are discussed.
Helium reemission during implantation of silicon carbide
Authors: Miyagawa S. , Ato Y. , Miyagawa Y.
Published: February 2003

Reemission has been measured during implantation of 1 keV and 20 keV helium ions in CVD SiC at room temperature and at 600 °C. The reemission behavior depends strongly on target temperature as well as ion energy, and there exists a close relationship between the reemission behavior and surface features. The flaking of CVD SiC is explained by crack propagation through the implanted layer, with gas pressure being the driving force for cracking. The effects on the reemission behavior of prebombardment with helium ions having continuous energy distribution have been also measured.
Argon implantation in GaAs: Damage and lattice site location analyses
Authors: Rai A. K. , Bhattacharya R. S. , Pronko P. P. , Ling S. C.
Published: February 2003

The recrystallization behavior of Ar+ implanted GaAs has been studied using transmission electron microscopy and Rutherford backscattering channeling and proton induced x-ray emission techniques. Ar+ implanted in undoped GaAs at 700 keV to a fluence of 5×1015 cm−2 has been used in the present investigation. Formation of microtwins are observed after annealing at 400 °C. These microtwins start to anneal at about 600 °C and disappear completely at about 850 °C at which point Ar bubbles are observed to form along with dislocations. Lattice location experiments show that the Ar atoms are randomly distributed in the lattice.
Radiation damage enhancement of the penetration of water into silica glass
Authors: Burman C. , Lanford W. A.
Published: February 2003

A dramatic increase in the rate of penetration of water into silica glass as a result of ion implantation with noble gas ions is reported. The damage caused by the implantation leads to the rapid uptake of water to a saturation concentration of hydrogen of approximately 1022 atoms/cm3. The effects of ion implant dose and ion mass are investigated. The results indicate that the mechanism responsible for this enhanced penetration is the creation of chemically reactive defects which greatly enhance the reaction between the water and the silica network.
Transition rates of Tb3+ in TbP5O14, TbLiP4O12, and TbAl3(BO3)4: An evaluation for laser applications
Authors: Colak S. , Zwicker W. K.
Published: February 2003

The properties of Tb3+ in crystals of three stoichiometric Tb compounds, viz., TbP5O14, TbLiP4O12, and TbAl3(BO3)4 have been studied by spectroscopic absorption and emission methods to evaluate these materials as hosts for Tb3+ laser applications. The absorption spectra between 50000 and 200 cm−1 at 300 °K, the emission spectra between 27000 and 14000 cm−1 at 300 °K, and the fluorescence decay characteristics of 5D4 emission at 300 and 5 °K are given. Because of cross relaxation, the 5D3 and 5G6 emissions in all three materials were concentration-quenched strongly with a similar behavior observed in other hosts. Quenching in the 5D4 states was negligible except for TbAl3(BO3)4 where moderate quenching was observed due to energy transfer to nonradiative traps. Transition rates between various states were calculated by using the Judd–Ofelt approach and a first order wavefunction set, and good fit was obtained between the calculated and experimental parameters. The transition rates were then used to find the emission cross sections of various lines.
High-output room-temperature pulsed operation for broad contact InP/In0.53Ga0.47As/InP lasers grown by molecular beam epitaxy
Authors: DeFreez R. K. , Elliott R. A. , Blakemore J. S. , Miller B. I. , McFee J. H. , Martin R. J.
Published: February 2003

Operating characteristics are described for broad contact double-heterostructure (DH) lasers grown by molecular beam epitaxy (MBE), with In0.53Ga0.47As active layers lattice matched to InP. These were operated at T≊293 K, with (low duty cycle) pulses of current from 1.5 to 3Ith. The lowest threshold current density, Jth ≊2800 A/cm2, is some 40% higher than an ideal cavity expectation. Under these strong pulse conditions, a multimode output was observed, with pronounced spatially filamentary characteristics. The output was plane polarized perpendicular to the active layer, indicative of TM mode dominance. This nontypical polarization, considered in conjunction with an indicated trend of external differential quantum efficiency increasing with length, is consistent with polarization-selective internal losses or polarization-dependent gain as the mode-controlling feature, rather than facet reflection losses.
Band-to-band Auger recombination in silicon based on a tunneling technique. I. Theory
Authors: Krieger G. , Swanson R. M.
Published: February 2003

Band-to-band Auger recombination in n+-type silicon is investigated. A new experimental approach for determining the band-to-band Auger coefficient that is based on the hot electrons generated in the recombination process is proposed and theoretically analyzed. Because this method is not sensitive to trap-assisted Auger recombination, or other types of recombination, it can yield information regarding the fundamental lifetime limits in heavily doped silicon. Experimental results are presented in a companion paper, Part II.
Impurity segregation during explosive crystallization of amorphous silicon
Authors: Bensahel D. , Auvert G. , Perio A. , Pfister J. C. , Izrael A. , Henoc P.
Published: February 2003

Impurity segregation in explosively crystallized a-Si presents two different behaviors depending on whether the intermediate liquid phase in the explosive process is large or narrow. This confirms the theories already published. In other words, a-Si explodes in a way similar to a-Ge. a-Si, however, presents a specific type of explosive crystallization explained by its higher nucleation rate with respect to a-Ge.
Spatial frequency analysis and matched filtering in electromagnetic nondestructive evaluation
Authors: Auld B. A. , Riaziat M.
Published: February 2003

The theory of electromagnetic flaw detection based on the Lorentz reciprocity theorem has been applied to quantitative modeling of the corrosion buildup problem in PWR steam generators. Formulation of the electromagnetic probe response in spatial Fourier transform domain clarifies the role of the probe as a spatial frequency filter. Examples are given of tailoring the spatial frequency response to achieve specific performance characteristics, such as liftoff noise discrimination and flaw shape characterization. The relationship of spatial frequency response to probe geometry is analyzed for two dimensional inductive and capacitive structures, and the use of signal compression for realizing good spatial resolution and improved signal-to-noise ratio in long probes is discussed.
Gaseous ion reactions in SiF4 and SiF4–D2 mixtures
Authors: Senzer S. N. , Lampe F. W.
Published: February 2003

The gas-phase reactions of D+2, D+3, SiF+, and SiF+3 with SiF4 and of SiF+ and SiF+3 with D2 have been studied in the center-of-mass energy range of 0.2–7 eV using a tandem mass spectrometer. Only one reaction of a silicon-containing ion with SiF4 was observed, namely the highly endothermic transfer of F− from SiF4 to SiF+. Hence the SiF4 molecule must be almost unique in showing a virtual absence of gas-phase ionic chemistry in pure SiF4 subjected to ionization. Several ion-molecule reactions were observed in the SiF4–D2 system but of these only the dissociative F− transfer from SiF4 to D2+ is exothermic. The almost total absence of exothermic ion-molecule reactions means that the ionic distribution pertinent to the plasma chemistry of the SiF4 and SiF4–H2 systems will be determined solely by the cross sections of the electron impact ionization processes.
Transmit versus receive gains for microwave dish antennas
Authors: Richter John L.
Published: February 2003

For the microwave dish antennas, the antenna gain when transmitting can be different, and is usually less, than that of the same antenna when receiving. The theory of the far field transmit and receive antenna gains is developed for the classical dish as well as for the general case. Aperture functions are derived for use in the integral form of the Fraunhofer diffraction equation. Both the aberration effects of the dish and the angular distribution of the feed are taken into account. Calculations of transmit and receive antenna patterns and gains are compared for the f/1 classical dish for various amounts of feed spillover.
Theoretical aspects of ionic loss in transmission lines magnetically insulated against electron loss
Authors: Swegle John
Published: February 2003

Experimentally, it has been established that negative ions cross the anode-cathode gap in transmission lines operating at sufficiently high currents that electrons emitted from the cathode would be magnetically insulated (i.e., deflected back to the cathode by the Lorentz force before reaching the anode). In this paper, a one-dimensional analysis of electron and negative ion emission from a cathode shows that electron emission decreases monotonically to zero as the ion emission increases to the maximum space charge limited value. A second one-dimensional calculation shows that in high current lines, neglecting electron emission, monopolar emission of ions is inhibited by the self-magnetic fields in the line, while bipolar emission is enhanced. Finally, a section is devoted to the approximate solution of several two-dimensional problems using some of the earlier results of this paper, as well as an empirical scaling law derived by other researchers relating the negative ion current density jn to the current per unit width in a line, J: jn =KJ3. In particular, fractional current loss as a function of distance from a load drawing a fixed current is found. An interesting byproduct of this calculation is the demonstration that the empirical scaling law leads to infinite line currents in a finite distance along a planar line, while such a divergence occurs only for certain parameter ranges on radial disk feed lines.
Transmission electron microscopy of GaAs permeable base transistor structures grown by vapor phase epitaxy
Authors: Vojak B. A. , Salerno J. P. , Flanders D. C. , Alley G. D. , Bozler C. O. , Nichols K. B. , McClelland R. W. , Economou N. P. , Lincoln G. A. , Murphy R. A. , Lindley W. T. , Johnson G. D.
Published: February 2003

Transmission electron microscopy has been employed to characterize GaAs permeable base transistor structures. Submicrometer-period tungsten base gratings fabricated on GaAs substrates by using either liftoff or etching techniques have been studied. Fabrication-related problems such as electrically isolated tungsten debris and poor tungsten adhesion to GaAs have been identified. The crystal quality of GaAs layers grown by vapor phase epitaxy over the tungsten base gratings has also been investigated. Both stacking faults and voids have been found in these layers. The concentration of voids, which have an elongated-bubble shape, depends on the orientation of the base grating on the GaAs surface. The effect of these structural imperfections on device performance is discussed.
Cuprous oxide–indium–tin oxide thin film photovoltaic cells
Authors: Fujinaka Masaharu , Berezin Alexander A.
Published: February 2003

We studied thin films of cuprous oxide deposited on glass coated with transparent conducting indium–tin oxide (ITO) films. The deposition of both Cu2O and ITO was made by rf sputtering in an Ar/O2 gas mixture. For the deposition of Cu2O a pure copper target was used and ITO films were deposited from a disk target, the halves of which were made of Sn and In, respectively. This allows variation of the stoichiometry of the deposited ITO film by changing the position of the substrate glass beneath the Sn/In target. X-ray diffraction of Cu2O films indicates the typical pattern of amorphous material. We were able to produce Cu2O films of different stoichiometry by varying the O2 to Ar ratio during rf sputtering. The maximum resistivity of the films corresponds to an ideal stoichiometry of Cu2O. An activation energy of 0.55 eV found from thermostimulated conductivity is related to excess Cu vacancies. The band gap found from the spectral dependence of the photovoltaic effect is 2.0 eV. The composition of ITO films was studied by Auger analysis and can be described as a variable composition mixture of SnO2+x and In2O3+y. To produce an Ohmic electrode, gold was evaporated on the top of the Cu2O film and hence the resulting structure of the photocell could be specified as ITO–Cu2O–Au, for which we propose a barrier band diagram. We studied the photovoltaic characteristics of the fabricated photocells under an incandescent lamp with ≂100 mW/cm2 output. The open-circuit voltage and short-circuit current of our cells were about 20–90 mV and 50 μA/cm2, respectively, and some dependence of the output characteristics on the composition of ITO film was observed. Conversion efficiency for thin films Cu2O/ITO cells was found to be substantially lower than for Cu2O/Cu Schottky barrier cells. This is tentatively attributed to small diffusion lengths and/or presence of interface recombination centers.
GaAs/(GaAl)As deep Zn-diffused channeled-substrate laser
Authors: Choi H. K. , Wang Shyh
Published: February 2003

GaAs/(GaAl)As channeled-substrate laser with deep Zn diffusion for tight current confinement is reported. It has extremely low threshold current (as low as 12 mA), high differential quantum efficiency, single lateral and longitudinal mode operation up to 10 mW. It has T0 of about 200 °C and the rate of threshold current change is only about 0.07 mA/°C from 10 to 70 °C.
Influence of deposition conditions on hydrogenated amorphous silicon prepared by rf planar magnetron sputtering
Authors: Webb James B. , Das S. R.
Published: February 2003

The electrical and optical properties of rf magnetron sputtered films of amorphous hydrogenated silicon (a–Si:H) have been measured as a function of rf power, argon and hydrogen partial pressures, and target-substrate distance. The properties of the deposited films show a very different dependence on preparation conditions than those prepared by nonmagnetron sputtering. The conductivity can be varied over ten orders of magnitude and the optical gap can be shifted by more than 1.0 eV by changing the deposition parameters. Furthermore, it is found that the electrical conductivity and optical band gap are strongly correlated. Thus, we have not been able to prepare undoped films with a given conductivity independently of the optical gap. The results of our measurments of the temperature dependence of the conductivity, the conductivity activation energy (ΔEσ), the shape of the optical absorption curve, and the optical gap (Eopt), suggest a direct connection between gap state density and the optical gap.
Flux-flow type Josephson oscillator for millimeter and submillimeter wave region
Authors: Nagatsuma T. , Enpuku K. , Irie F. , Yoshida K.
Published: February 2003

An oscillator which utilizes the effect of the vortex motion in long Josephson tunnel junctions, i.e., flux flow, has been presented in millimeter and submillimeter wave region. An electromagnetic wave generated by the oscillator is detected with a small tunnel junction as a detector with a refined coupling configuration. Quantitative evaluation of the detected power showed that the detected power attained the value of 10−6 W in the frequency range between 100 and 400 GHz, which is far superior to previous results. Frequency and magnetic field dependences of the present system were also measured, which showed that the output power was able to be controlled by the dc magnetic field. The present oscillator will be promising as the local oscillator in the integrated Josephson receiver systems.
Transient flux flow voltages in type II superconductors
Authors: Anjaneyulu Y. , Joiner W. C. H. , Lee Jean-Liong , Sission Kevin
Published: February 2003

Transient flux flow voltage are observed when constant current is switched on in a type II superconductor at low magnetic fields. The nature of the transients is related to the method of formation of the flux line lattice. The transients are attributed to changes which occur in the flux line lattice as inhomogeneities created at the time of formation of the lattice move out of the sample as a result of flux flow. A model is developed to describe this process which includes the requirement that when dissimilar regions of flux move across the sample, the rate of flow must be the same for these regions, so that an equipotential exists across the sample width. For currents below the equilibrium critical current, excellent fits to this model are obtained for our data.
Mössbauer effect and magnetism of single domain Fe3O4 particles in ferrofluids
Authors: Tari A. , Popplewell J. , Charles S. W. , Bunbury D. St. P. , Alves K. M. B.
Published: February 2003

Three ferrofluids, consisting of suspensions of Fe3O4 particles of ≂100–200 Å diameter in diester, hydrocarbon, and water have been investigated at temperatures 4.2–300 K by means of Mössbauer effect and magnetic measurements. The magnetic data displays almost all the features observed in the spin glasses. The Néel model is used to explain the behavior of the fluids. From the temperature variation of the initial susceptibility and the isothermal remanence, K=(3.5±0.7)×105 erg/cc and D0=(80±5) Å are obtained for the anisotropy constant and the median diameter, respectively, of the diester based ferrofluid. The ac susceptibility gives K=3×105 erg/cc and D0=92 Å. For the water based ferrofluid measurements give K=1.5×105 erg/cc. Values obtained from Mössbauer measurements for K and D0 agree with those obtained from magnetization–susceptibility data.
Induced emission cross section of Nd:Y3Al5O12 grown by floating zone method
Authors: Sekita Masami , Kimura Shigeyuki
Published: February 2003

Optical spectra and emission lifetimes are measured for three Nd:Y3Al5O12 crystals grown by the floating zone method. The properties are almost the same as those of crystals grown by the conventional Czochralski method. The induced emission cross sections obtained for the three samples are 7.4, 5.3, and 7.0×10−19 cm2. These values are comparable to those reported so far.
Photoluminescence and doping in liquid phase epitaxial GaAs1−xSbx
Authors: Castaño J. L. , Piqueras J.
Published: February 2003

Undoped, Ge-, and Sn-doped GaAs1−xSbx grown by liquid phase epitaxy have been investigated by means of photoluminescence. Four main peaks have been observed at 11 °K in the undoped samples. One of them K1 at 1.513 eV in GaAs and the two, K2 and K3, at 25 and 62 meV, respectively, below the band gap energy show an evolution with x parallel to the band gap variation. The remaining one at 1.31 eV does not change appreciably with the Sb content.
Optical absorption and thermoluminescence in LiF TLD-100
Authors: Caldas Linda V. E. , Mayhugh Michael R. , Stoebe Thomas G.
Published: February 2003

The thermoluminescent (TL) properties of many LiF samples have demonstrated a strong influence on trace impurities and impurity content on the TL process. Hence, the general validity of any particular model must be tested against its applicability in a standard material such as Harshaw LiF (TLD-100). In this paper the validity of the use of Harshaw LiF(54) by Mayhugh et al. in their model development for the TL process in LiF is demonstrated by comparing the TL and optical properties of LiF(54) with TLD-100. The specific properties of optical absorption bands at 310 and 380 nm, the F band near 250 nm, and the Z3 band near 225 nm are intercompared with observed TL peaks in both materials. Both the gamma and uv-exposure behavior of the Z3 center demonstrates a direct relationship between Z3 and TL peak 10, while no direct conversion between Z3 and the 310-nm band is observed in TLD-100. These results do not support recent models identifying Z3 with TL peak 6 and Z2 with the 310-nm band (and TL peak 5); this is probably due to differences in purity and defect state in the LiF samples used by other investigators, emphasizing the need for standardization of materials in this system.
Evidence for plasma jet formation in long-pulse laser irradiation of thin planar Al targets
Authors: Anthes J. P. , Matzen M. K.
Published: February 2003

Thin planar aluminum targets were irradiated with 8-nsec-duration low-intensity (∼3×1013 W/cm2) glass laser pulses in order to analyze the plasma expansion from both the front and back-target surfaces. An array of vacuum-ion calorimeters and Faraday cup charge collectors was used to determine the conversion from incident laser energy to plasma kinetic energy and to determine the ion mass balance of the laser-produced plasma. Our experimental results do not agree with the ablation structure predicted by simple models or 1-D numerical simulations. The experimental results and 2-D calculations indicate that a jet of plasma forms on the back target surface and ablative acceleration of these thin-foil targets does not occur.
Behavior of positive ions ejected from laser-irradiated CdS
Authors: Namiki A. , Watabe K. , Fukano H. , Nishigaki S. , Noda T.
Published: February 2003

The dynamic behavior of ions ejected by pulsed nitrogen laser irradiation of the single-crystal CdS have been ivestigated with a dynamic mass spectroscopic method. The energetic ions are generated through a process different from that of slow neutrals. The ion produced below 80 mJ/cm2 laser power is created at the surface and accelerated by a Madelung potential, reaching the kinetic energy of 100 eV. At a higher power region, relatively slow cadmium ions showed a Maxwellian velocity distribution suggesting the laser-generated gaseous plasma. Three possible mechanisms for ion formation are presented.
Dependence of the microstructure of amorphous silicon thin films prepared by planar rf magnetron sputtering on deposition parameters
Authors: Das S. R. , Williams D. F. , Webb J. B.
Published: February 2003

Amorphous silicon films, prepared by planar rf magnetron sputtering, in both hydrogenated and unhydrogenated forms, are found to exhibit three distinct types of microstructure depending on the growth conditions: (a) no resolvable microstructure down to 10 Å; (b) islands of 50–200 Å lateral dimensions separated by a network of lower density; (c) a two level pattern wherein conglomerates of 50–200 Å islands form columnar regions of 300–500 Å lateral dimensions interspersed by a more pronounced low density network. The argon pressure during growth has the dominant influence on the evolution of the microstructure. Type (a) microstructure is obtained at low (≤ 3 mTorr) argon partial pressure irrespective of rf power level, hydrogen partial pressure, and substrate temperature and type (b) and (c) microstructures are observed at higher argon partial pressures (≥10 mTorr). Increasing rf power and substrate temperature at high argon partial pressures result in an enhancement of the microstructural features. Addition of hydrogen enhances the microstructure at low rf power levels and suppresses the microstructure at high rf power levels.
Electrical properties of S implants in GaAs activated by infrared rapid thermal annealing
Authors: Kuzuhara M. , Kohzu H. , Takayama Y.
Published: February 2003

S-implanted GaAs at room temperature was annealed by several seconds radiation from halogen lamps. Differential Hall effect/sheet resistivity measurements have been used to study the annealing behavior and electrical carrier concentration profiles of S-implanted GaAs. Electrical activation was found to increase with increasing annealing temperature up to 1100 °C. A maximum electrical activation of 78% was obtained for a dose of 5×1013 cm−2. Also, more than 5×1018 cm−3 peak carrier concentration was obtained for a dose of 1×1014 cm−2, indicating about three times higher peak concentration than that obtained after conventional furnace annealing. For higher doses, the implanted S in the annealed GaAs does not follow Gaussian distribution even after rapid annealing. Damage-enhanced outdiffusion of S is considered to be responsible for this result.
Low temperature annealing of Be-implanted GaAs
Authors: Kwun Sook-Il , Hong Chong-Han , Spitzer W. G.
Published: February 2003

Infrared reflection and transmission measurements of GaAs implanted with large fluences of Be ions have been made as a function of post-implantation annealing temperature. Annealing up to 400 °C resulted in decreases in the lattice disorder responsible for changes in the dielectric constant. This decrease appears to take place uniformly throughout the disordered layer rather than by an epitaxial process. Annealing at 400 °C for 2 h returns the dielectric constant to essentially the preimplantation value with no significant carrier activation being observed. Carrier activation is observed only after prolonged annealing at 400 °C, i.e., ≳50 h. Annealing for 1 h at 450 °C also produces measurable carrier activation. These results are in general accord with prior electrical data and transmission electron microscope measurements and suggest that the removal of the disorder-induced changes in the dielectric constant and the activation of free carriers might involve different annealing processes.
Electrical response of relaxing dielectrics compressed by arbitrary stress pulses
Authors: Lysne P. C.
Published: February 2003

The theoretical problem of the electric response of biased dielectrics and piezoelectrics subjected to planar stress pulse loading is considered. The materials are taken to exhibit dielectric relaxation in the sense that changes in the polarization induced by electric fields do not occur instantaneously with changes in the fields. While this paper considers arbitrary stress pulse loading of the specimen, examples that are amenable to projectile impact techniques are considered in detail. They are shock reverberation, thin pulse, and ramp loading experiments. It is anticipated that these experiments will play a role in investigations of dielectric relaxation caused by shock induced damage in insulators.
Dielectric relaxation in insulators slightly damaged by stress pulses
Authors: Lysne P. C.
Published: February 2003

The relationship between incipient stress-pulse-induced damage and the electrical response of a piezoelectric, ferroelectric, or electrically biased dielectric is examined. The model assumes the presence of isolated inclusions of damaged material which are conducting and which may grow. Virgin insulating material surrounds the inclusion . Sillars’ model of an inhomogeneous dielectric is invoked to yield parameters of an electrically equivalent, relaxing dielectric. These parameters are used to generate the electrical response caused by propagating stress pulses. Qualitative agreement with current histories obtained from experiments on X-cut quartz is obtained, quantitative results await further experimentation.
Interdiffusion in β phase Cu–Al alloys
Authors: Romig A. D.
Published: February 2003

The diffusion behavior of β phase Cu–Al has been studied at 800, 850, and 950 °C using the experimental approach and analysis scheme of Kirkendall and Darken. Diffusion couples were made using the window frame technique and concentration profiles were determined by electron probe microanalysis. The chemical diffusion coefficient, D̃ was found to be D̃=0.65 exp(−42200/RT) cm2/s. The diffusivity was observed to be independent of composition over the range 11–13 wt. % Al. The self-diffusion coefficients DCu and DAl were determined to be DAl =0.13 exp(−38900/RT) cm2/s and DCu =2.2 exp(−43400/RT) cm2/s. All activation energies are in calories/mole.
Reactively sputtered titanium carbide thin films: Preparation and properties
Authors: Eizenberg M. , Murarka S. P.
Published: February 2003

The low resistivity and refractory nature of titanium carbide makes it potentially useful as a diffusion barrier in thin film metallization schemes. In the present investigation, deposition and properties of thin titanium carbide films have been investigated. The films were deposited by reactive radio frequency sputtering in methane–argon mixtures on a variety of substrates. The effects of methane to argon ratio, total sputtering pressure, and power on the film deposition rate, composition and properties were determined. There were interactive effects of these parameters on the composition and properties of these films. Resistivity increased with carbon content; for Ti/C≥1 it was ∼200 μΩ cm. Stress that was compressive was maximum in the nearly stoichiometric TiC film. Grain size was small in all films, especially so in carbon rich films. All stoichiometric titanium carbide films were resistant to HF solutions. Films with TiC/≥1 dissolved easily in ethylene dinitrilo tetra acetric acid (EDTA) solution.
Pressure induced conduction and valence band shifts in InP and GaAs from measurements at semiconductor–electrolyte interfaces
Authors: Zurawsky W. P. , Littman J. E. , Drickamer H. G.
Published: February 2003

The effect of pressure on the band gap and flatband potential of n- and p-type InP and GaAs was studied to 10 kbar at 300 K. For both InP and GaAs it was determined that the increase of the energy gap of the direct transition is to first order due to an increase in energy of the conduction band edge.
Inductive response of metallic spheres and spherical shells
Authors: Callarotti R. C. , Schmidt P. E.
Published: February 2003

We have derived the theory for the electromagnetic transient response of metallic spheres, spherical shells, and composite spheres (composed of two materials with different conductivities). We have related the dominant time constant of the voltage at a secondary coil wound around the samples, with their physical characteristics: conductivity, permeability, and geometrical factors. We show that a thin spherical shell under certain conditions can be considered as one time constant system and we derive the values of the resistance and the inductance of the shell equivalent circuit. We have obtained experimental results for aluminum and brass spheres, and we have evaluated experimentally the effect of different primary coil designs.
Theoretical and experimental study of swept line electron beam annealing of semiconductors
Authors: Banerjee S. , Streetman B. G.
Published: February 2003

The temperature distribution in a rectangular sample as a function of time and position during swept line electron beam (SLEB) annealing has been calculated. Beam penetration effects have been included by using the Monte Carlo method and the temperature distribution has been obtained from Green’s function techniques and the method of images. The effects of various beam parameters on the temperature distribution have been studied. The results are correlated with experimental studies of the electrical activation of Be in GaAs during SLEB annealing. The annealing is shown to be governed by a relation of the form: Activated fraction=(Dwell time)×(3840e−(0.535/kBT) ).
Measurement of bulk photovoltaic and photorefractive characteristics of iron doped LiNbO3
Authors: Grousson R. , Henry M. , Mallick S. , Xu S. L.
Published: February 2003

Birefringence changes induced in LiNbO3:Fe by a light beam have been measured to determine the photovoltaic characteristics such as the saturation value of space charge field, dielectric relaxation time, the probability φ of creating a free electron by an absorbed photon and the mean migration length L of the electron. These quantities are determined for different wavelengths covering the region 400–600 nm. The product φL that determines the photorefractive sensitivity of the material increases with decreasing wavelength. This increase is largely due to the increase of φ, the variation of the migration length being relatively small.
Thermal-resistive current filamentation in the cathode plasma of a pinch-reflex diode
Authors: Tripathi V. K. , Ottinger P. F. , Guillory J.
Published: February 2003

Electron current flow drawn off a hollow cylindrical cathode in a pinch-reflex ion diode is observed to have a filamentary structure. Such filamentation can lead to nonuniform anode turn on and ion emission. Consequently, ion beam brightness is degraded. In this context a purely growing thermal-resistive instability in the cathode plasma is examined. The instability causes current filamentation and grows on a time scale comparable to the electron–ion energy equilibration time. Electron inelastic collisions have a stabilizing influence on the instability.
Kinetics of formation of krypton-halogen atom exciplexes in electron beam irradiated gases
Authors: Cooper Ronald , Denison Lynette S. , Zeglinski Philip , Roy Colin R. , Gillis Hugh
Published: February 2003

The formation of KrCl*, KrBr*, and KrF* exciplexes, in electron beam irradiated mixtures of krypton with either CF3Cl, CF3Br, SF6, or CF4, are observed to be formed by two distinct and kinetically resolvable time-dependent processes. The rate of one process is total electron beam energy (dose per pulse) independent but dependent on the partial pressures of the halogen source. This process is attributed to a reaction between high electronic excited states of krypton and the halogen source. The second process is dependent on the total absorbed electron beam energy per pulse and is shown to be due to ion recombination processes. Specifically, the formation is due to a combination of krypton positive ions and halogen negative ions, the latter being formed by dissociative electron capture by the halogen source. This process produces KrF* in high vibrational levels.
Boundary conditions at grain boundaries
Authors: von Roos Oldwig
Published: February 2003

Grain boundaries in polycrystalline semiconductor material are frequently idealized as surfaces possessing a characteristic surface recombination velocity. Minority carrier densities generated by external sources (electron beams, light, etc.) in polycrystalline p–n junctions must satisfy certain boundary conditions at these grain boundaries which will be derived. It will also be shown that a ‘‘folding technique’’ introduced recently to deal with this problem is of limited value.
Current injection in an insulator with specially distributed shallow traps
Authors: Sharma Y. K. , Sharma R. N. , Raghav V. S.
Published: February 2003

The approximate current-voltage characteristic has been given for the single injection current in an insulator containing specially distributed shallow traps in carrier density dependent mobility regime. It is shown that a cube power law for current-voltage characteristic is valid in space-charge-limited trap free regime.
Intrinsic interface states as extended deep traps: Ge/GaP and Si/GaP
Authors: Buisson Jean Pierre , Kykta Martin P. , Dow John D. , Beres Richard P. , Allen Roland E.
Published: February 2003

Electronic interface state dispersion curves E(k̄) are predicted for (110) Ge/GaP and Si/GaP interfaces, and are found to overlap the mutual fundamental band gaps. Such bound interface states can act as extended deep traps.
Critical transition region smearing in heterogeneous amorphous ferromagnets
Authors: Tyagi Somdev
Published: February 2003

The high field magnetization versus temperature measurements under certain conditions can be totally insensitive to the magnetic heterogeneity in an amorphous ferromagnet, making them less informative than the low field measurements which reveal such heterogeneity.
Pyroelectric measurements of (1-reflectivity) in the visible for metallic films
Authors: Burns G. , Dacol F. H. , Melcher R. L.
Published: February 2003

The use of pyroelectric sensors to measure the optical properties of thin metallic films is reported. New results on the pyroelectric responsivity versus temperature in ferroelectric Pb5Ge3O11 are reported.
Index of refraction of AlAs-GaAs superlattices
Authors: Leburton J. P. , Hess K. , Holonyak N. , Coleman J. J. , Camras M.
Published: February 2003

The index of refraction of AlAs-GaAs superlattices is studied both experimentally and theoretically and is compared to the index of the corresponding ternary alloy obtained by intermixing of the superlattice. We find that the index of a superlattice can be 5%–6% higher than the index of the alloy due to zone folding of the states around Γ.
Correlation of photoluminescence and symmetry studies with photoexcitation and decay processes of infrared active defects in Si
Authors: Vidinski W. J. , Steckl A. J. , Corelli J. C.
Published: February 2003

Defects introduced in silicon by neutrons and ions which give rise to infrared active electronic defect absorption bands after heat treatment to 500 °C were studied using a dual beam optical method. The measurements were made in the 11–90 K temperature range on four defect bands found in the 900 (11.1)–1100 cm−1 (9.09 μm) region of the infrared spectrum. The studies yield results on the capture cross sections of photoexcited electrons from defects which lead to a model of a defect having three different charge states. These cross sections are much smaller than those reported for the photoionization cross sections of chemical impurities such as Au in silicon. The states found in this study can be identified with photoluminescence peaks reported by others near 1 and 0.76 eV. Additionally, there are two different symmetries assumed by the defects responsible for the defect absorption bands.
Laser beam heating and high temperature band-to-band luminescence of GaAs and InP
Authors: Kirillov D. , Merz J. L.
Published: February 2003

High temperature band-to-band luminescence of GaAs and InP excited by an argon ion laser beam was used as a probe to measure the temperature inside of the laser spot. First, the high temperature luminescence with external heating by an oven was studied, and the resulting dependence of luminescence and band gap on the temperature was used to investigate the case of laser heating. It was found that lattice heating is the most important influence on the luminescence spectra for strong cw laser excitation, and that the temperature of the lattice can be determined with high precision due to the high sensitivity of the luminescence band energy to the lattice temperature. The temperature inside of the laser spot as a function of laser power was measured. The temperature is lower than anticipated from the current theories for cw laser heating. This disagreement can be explained by the contribution of photoexcited carriers to the thermal conductivity, which was not considered by theories.
Manganese concentration dependent saturation in ZnS:Mn thin film electroluminescent devices
Authors: Törnqvist R.
Published: February 2003

The decay rate of the yellow emission in ZnS:Mn thin film electroluminescent devices increases at high luminance levels and a larger increase is observed for higher manganese concentrations. A stronger saturation of the emission is also observed when the manganese concentration is high. The experimental results suggest nonradiative decay caused by an interaction between excited Mn2+ which occurs by energy transfer via unexcited Mn2+. An increase in the current density in the ZnS:Mn layer is observed simultaneously with the higher decay rate of the emission, which indicates that free electrons are created in the interaction between excited Mn2+.
Equivalent circuit analysis of a system of coupled helical transmission lines in a complex environment
Authors: Singh V. N. , Basu B. N. , Pal B. B. , Vaidya N. C.
Published: February 2003

The complex boundary value problem of a system of coupled transmission lines which takes into account the effects of the dielectric and metal shell environment is solved by a simple equivalent circuit analysis. The results are compared with those for a simple system of coupled helices in free space now available in the literature. The effects of the various environmental parameters—like the thickness of the dielectric sleeve for the outer helix, the ratio of the outer helix-to-inner helix radii, the ratio of the outer helix-to-inner helix contangents of the pitch angle—are studied on the variation of the optimum length with frequency for a system of helical couplers as used in a traveling-wave tube.
Microwave generation from rotating electron beams in magnetron-type waveguides
Authors: Destler W. W. , Kulkarni R. , Striffler C. D. , Weiler R. L.
Published: February 2003

The production of high power microwave radiation at high harmonics of the electron cyclotron frequency by the interaction of a rotating electron beam with a magnetron-type conducting boundary has been studied theoretically and experimentally using a 2-MeV, 1–2-kA, 10-ns electron beam pulse. Approximately 10% of the electron beam power has been converted to microwave radiation at the 12th harmonic, and about 2% at the 20th harmonic. Radiation characteristics are in good agreement with a theoretical analysis of the resonant interaction of a beam mode with the modes of the conducting boundary system. Radiation from rotating beams in ‘‘glide-symmetric’’ boundary systems is also reported.
Study of the crystalline surface of Metglas 2605 CO
Authors: Choi M. , Pease D. M. , Hines W. A. , Budnick J. I. , Hayes G. H. , Kabacoff L. T.
Published: February 2003

X-ray studies using a diffractometer and Read camera are reported for Metglas 2605 CO. A crystalline surface layer, which extends into the sample ≲3 μm occurs on only the substrate wheel side of the as-quenched ribbon. Most of the crystallites consist of an α-iron phase and are preferentially oriented in a fiber texture configuration; the fiber axis being a mixture of the [100] and [110] directions, and normal to the ribbon surface. A small amount of non α-iron crystallinity is also present. The crystalline surface layer does not appear to influence the high value of the magnetomechanical coupling factor obtained through magnetic annealing.