bluuebunny/crossref_metadata_2025 huggingface dataset:
A model for the time evolution of the internal friction observed in some fcc metals under irradiation: The peaking effect
Authors: Caro J. A. , Glass N. E. , Mondino M. A.
Published: February 2003

The time evolution of the internal friction that has been observed in certain fcc metals (Cu, Ag, Al) under irradiation, and known generally as the ’’peaking effect,’’ has been shown by a recent set of experiments1–2 to be inadequately explained by the existing models which describe the energy dissipation through dislocation motion by the well-known analogy to a vibrating string with viscous damping. A phenomenological model is thus proposed here that introduces a source of energy dissipation through dislocation motion which is independent of the dislocation velocity, viz., nonviscous damping. With dislocation pinning by thermally diffusing point defects and strain- dependent depinning also included in the model, the observed internal-friction dependence upon irradiation time as well as upon the applied strain amplitude and frequency are well described.
Submicron eutectic thin-film structure
Authors: Cline Harvey E.
Published: February 2003

Pb-Sn, Cd-Pb, and Al-Al2Cu eutectic thin films were directionally solidified at rates between 0.0015 and 0.15 cm/sec with both a lamp and a laser heat source to fabricate fault-free submicron periodic structures. A transition from lamellar to cellular structures with increasing solidification rate was observed with a thermal gradient of 200 °C/cm applied with the lamp heat source. Cells did not form with the increased thermal gradient produced by the laser heat source, 8000 °C/cm. Spacings as fine as 0.1 μ were observed in the Cd-Pb eutectic. A maximum theoretical growth rate was estimated which corresponds to a spacing of 80 Å.
Formation of thin oxide on polycrystalline silicon
Authors: Horiuchi Masatada
Published: February 2003

The growth of very thin (15–80 Å) oxides on polycrystalline silicon films at 850–1050 °C in 10−3 atm oxygen partial pressure diluted by nitrogen is studied by ellipsometry. The oxidation kinetics are explained by the inverse-logarithmic law which governs very thin oxide growth on single- crystal silicon. The Arrhenius expression which can be evaluated from the oxidation velocity has a break point about 900 °C. The high temperature activation energy roughly coincides with that of single-crystal silicon.
Characterization and annealing behavior of deep levels in CdTe epitaxial layers
Authors: Sitter H. , Heinrich H. , Lischka K. , Lopez-Otero A.-
Published: February 2003

Deep defect levels play an important role in determining minority carrier lifetimes in CdTe photovoltaic devices. Much work has been done on the investigation of defects in bulk CdTe. In this paper we report on results obtained in CdTe thin epitaxial films, deposited on BaF2 and PbTe by hot-wall epitaxy. Deep Level Transient Spectroscopy was used to measure the energy levels, the capture cross sections, and concentration profiles of the defect levels. The measurements were performed on PbTe/CdTe heterojunctions and Au/n-CdTe Schottky barriers. Six levels were identified in the CdTe layers (E1 = 0.20 eV, E2 = 0.36 eV, E3 = 0.34 eV, E4 = 0.24 eV, E5 = 0.46 eV, E6 = 0.64 eV). By measuring the capture cross section separately an activation energy of 60 meV for the capture cross section of level E3 was found. The concentration of some of the defects could be reduced by annealing.
An investigation of the deep level photoluminescence spectra of InP(Mn), InP(Fe), and of undoped InP
Authors: Eaves L. , Smith A. W. , Skolnick M. S. , Cockayne B.
Published: February 2003

Deep level photoluminescence bands related to Mn and Fe in InP are investigated. In InP(Mn) a strong broad band peaking at 1.15 eV and with phonon structure at 1.184, 1.145, and 1.107 eV is observed. A broad band peaking at 1.10 eV with weak phonon structure at 1.135, 1.098, and 1.062 eV is observed in InP(Fe). Several undoped InP crystals also reveal a band identical to that seen in InP(Mn) suggesting that Mn may be an inadvertent impurity. In these undoped samples and also in InP(Cr) the intensity of this band is greatly enhanced after thermal annealing (750 °C), suggesting that Mn may be diffusing to the surface. Mn has been previously reported to behave in this way in GaAs. Other unidentified deep level photoluminescence features in undoped material are also observed at 0.765 and 1.284 eV. Fe is detected as an inadvertent impurity in some undoped samples from studying the Fe2+(5T2−5E) internal transition.
Occupation statistics of dislocation deep levels in III-V compounds
Authors: Masut Remo , Penchina Claude M. , Farvacque J. L.
Published: February 2003

Making use of the dielectric function of the material one calculates, in a very simple way, the energy corresponding to the electrostatic interaction of carriers trapped along a line of periodically spaced sites (e.g., a dislocation). A qualitative discussion of possible dislocation cores permits a representation of two situations which should correspond roughly to the actual cases of ’’60°’’ and ’’screw’’ dislocations. Calculations are carried out numerically self-consistently. Results are presented for n, p, and compensated InSb.
The effect of initiator duration on pulsed chemical-laser performance
Authors: Mirels Harold
Published: February 2003

The effect of initiator pulse duration on the performance of a pulsed chain reaction chemical laser is investigated using a two-level vibrational model. Analytic results are presented for a saturated laser in the limits of weak and strong initiation. The initiator is assumed to provide a uniform (e.g., electron beam), parabolic (e.g., flash-lamp), or power-law variation of F-atom production rate ḞB with time. Laser performance is presented as a function of tB /te, where tB and te are initiator and laser pulse times, respectively. In the weak initiation regime, an increase of tB /te from zero to one results in a decrement in laser output energy of 20 and 33 (1)/(3) % for a flash-lamp and electron-beam initiator, respectively. In the strong initiation regime, an increase of tB /te from zero to one results in an energy decrement of only 5 and 10% for a flash-lamp and electron-beam initiator, respectively. In each case, the laser-pulse time te is increased by a factor of 2 as tB /te increases from zero to one. For strong electron-beam initiation, peak laser intensity occurs at the end of the initiation pulse when tB /te?2/3, and occurs in the time interval 0.630?t/te?2/3 when tB /te≳2/3.
On tunneling in metal-oxide-silicon structures
Authors: Weinberg Z. A.
Published: February 2003

The analysis of Fowler-Nordheim tunneling data in metal-oxide-silicon structures is reviewed. It is concluded that a parabolic dispersion relation for SiO2 and an electron effective mass of mox = 0.5m provide the best description of the experimental results, this conclusion is consistent with recent band structure calculations for SiO2. Also included is a brief discussion of the transverse momentum conservation issue for tunneling from silicon of 〈100〉, 〈110〉, and 〈111〉 orientation into SiO2.
Annealing and light induced changes in the field effect conductance of amorphous silicon
Authors: Powell M. J. , Easton B. C. , Nicholls D. H.
Published: February 2003

We have measured the field effect conductance of α-Si:H and its dependence on annealing to 180 °C and illumination with white light. We find that illumination produces changes in the field effect conductance which are completely reversed by annealing. Illumination produces a decrease in the off conductance between a factor of 5 and 30 times, together with a shift of the threshold voltage. We interpret the effect of illumination as a modification of the density or occupancy of deep states in such a way that the bulk Fermi level is moved with respect to the conduction band mobility edge. Space-charge regions can exist at either or both interfaces of the α-Si:H film and these are very sensitive to interface conditions. The magnitude of the surface band bending is modified by electron trapping in the gate insulator (SiN), which is brought about by bias- temperature stressing. Annealing to 180 °C causes the detrapping of excess electrons in the SiN layer, reversing the effect of positive bias-temperature stressing.
Electrical properties and grain size of phosphorus i
n s
i
t
u doped and cw laser annealed polycrystalline silicon films
Authors: Ternisien d’Ouville T. , Vu D. P. , Perio A. , Baudrant A.
Published: February 2003

cw laser annealing is performed on phosphorus in situ doped polycrystalline silicon films prepared for a silicon gate technology. Electrical properties and grain size of laser annealed polysilicon films are investigated for different laser power and scan rate conditions using Hall measurements and transmission electron microscopy. Depending on laser power and scan rate used, the mean grain size of polysilicon films is increased by recrystallization in either a solid phase regime (SPR) or a liquid phase regime (LPR). A previous thermal annealing step is necessary in order to obtain controllable liquid phase recrystallization. Sheet resistance reduction, due to the electrical activation of phosphorus atoms and an increase of mobility, is more important in LPR than in SPR. Indeed, desegregation of phosphorus atoms is completed as well in both regimes while effective mobility approaches single crystal value in LPR only. A carrier-trapping model shows that improvement in mobility is directly governed by the increase of mean grain size in polysilicon films. For the doping levels encountered in our films, the mean grain size sufficient to approach single crystal mobility is obtained only in LPR.
Shunted Josephson tunnel junctions: High-frequency, self-pumped low noise amplifiers
Authors: Calander N. , Claeson T. , Rudner S.
Published: February 2003

The high-frequency amplification properties of transformer coupled, resistively shunted Josephson tunnel junctions have been investigated. The importance of the shunt loop inductance is stressed. It allows a high cutoff frequency, of significance for good high-frequency performance. The self-pumped parametric amplifier showed none of the excessive noise rise, which has hitherto plagued the development of externally pumped Josephson junction amplifiers. Around 10 GHz, we estimated a noise temperature less than 30 K for an amplifier pumped by a Josephson oscillation with a frequency well above twice the signal frequency. The corresponding gain of 5 dB may be increased in a better impedance matched circuit. The gain was very stable against variations in the bias conditions. A gain-bandwidth product as high as 0.3 was registered. The experimental results agreed well with the established theory for self-pumped parametric Josephson amplifiers. It should be possible to extend the low noise amplification by this device to mm wave frequencies. A relaxation oscillation occurred at a subharmonic of the Josephson frequency when the shunt loop inductance became large. The amplification in this mode followed closely the predictions of a simple model, where the signal modulated the switching of the sawtooth-like (relatively low frequency) relaxation current. Gains of about 15 dB were measured around 10 GHz, but the amplification was sensitive to bias conditions and noisy in this case where the relaxation frequency fell well below the signal frequency. Much improved properties were registered when the inductance was decreased so that the relaxation frequency approached the Josephson frequency and exceeded twice the signal frequency. The behavior then resembled that of a Josephson mode parametric amplifier, but the high content of harmonics of a relaxation oscillation meant that the amplifier became noisier due to converted noise from the many idler frequencies.
A strain-induced phase transformation in bronze-processed Nb3Sn?
Authors: Suenaga M. , Welch D. O.
Published: February 2003

The superconducting critical temperatures and magnetic fields of bronze-processed monofilamentary Nb3Sn wires flattened by rolling before reacting were, respectively, ∼13.5 K and 12 T, compared with values ∼16 K and 18 T for similarly processed circular (unflattened) wires. The interpretation of these results is discussed as either (i) the consequence of a strain- induced phase transformation or (ii) the result of the normal strain dependence of the critical properties of Nb3Sn and the triaxial nature of the residual strain state of the composite. A clear choice between the two possibilities is not possible on the basis of the present evidence, but the results underscore the inadequacy of describing the state of internal strain produced by differential thermal contraction in terms of a single value of ’’precompression,’’ as is commonly done.
Generation of magnetostatic surface waves by a microstrip
Authors: Emtage P. R.
Published: February 2003

The distribution of current across the width of a microstrip line can be severely distorted by a neighboring magnetic medium. The strength of the emission of magnetostatic surface waves by a narrow microstrip is calculated, taking approximate account of this distortion. Theory and observation agree that the effect is large (more than a factor of 2) in the upper part of the band of surface wave frequencies.
Absorption measurements of laser optical materials by interferometric calorimetry
Authors: Itoh Masahide , Ogura Iwao
Published: February 2003

The widespread use of high-power lasers requires further studies of the very low loss materials. The development of such materials has led to the progress in the measurement technique of small absorption coefficients. We propose a new technique of measuring bulk and surface absorption coefficients using an interferometric calorimetry. It is important to separate surface absorption from bulk absorption, for recent studies have revealed that surface damage occurs earlier than bulk damage. The sample exposed to a laser beam absorbs the light proportional to its absorption coefficient. Change in optical path arises because the index of refraction and the sample thickness depends on temperature. We can obtain the bulk and the surface absorption coefficients by measuring this change of optical path length by using the Michelson interferometer or the holographic interferometer.
Deep level profiles in boron implanted n-Si
Authors: Qin Guo-Gang , Li Ming-Fu , Sah Chih-Tang
Published: February 2003

The annealing temperature (280–810 C) dependences of the concentration profiles of the majority carriers (electrons), the main deep level at EC−400 mV, and the implanted boron ions are reported in 0.23 Ω cm (3.1×1016 cm−3) phosphorus-doped n-type silicon which was implanted with 5.0×1011 cm−2 of 200 KeV boron ions. A new constant-capacitance voltage transient (CCVT) method and a new many-deep-level CCVT theory are employed to obtain the deep level profiles whose concentrations are comparable to that of the phosphorus dopant impurity. The measured profile of the implanted boron ions, activated at 810 C, agrees with the projected range theory. Seven peaks are observed above 77 K in the deep-level capacitance transient spectra. The major peak at EC−400 mV has a concentration profile that lags behind the boron ion profile and it anneals rapidly between 420 and 430 C. The broadness and the annealing behavior of the majority carrier concentration profiles suggest the presence of at least two high-concentration deep acceptor-like levels below the midgap and at least one of them is a multiple charge state of the EC−400 mV defect level in the upper half-gap.
Current-voltage response of tandem junction solar cells
Authors: Potter R. R. , Sites J. R. , Wagner S.
Published: February 2003

A model tandem junction solar cell is compared with experimental results from the monolithic n-Si/SnO2/n-CdSe/electrolyte tandem system and from its constituent cells, n-Si/SnO2 and n-CdSe/electrolyte. Inclusion of the effects of series resistance and partial shunting of one or both active junctions produces a model that adequately describes the experimental cell. Both the voltage addition principle and the expected response to the tandem cell to different wavelengths are confirmed. The implications for tandem junction solar cell development are discussed.
A condition for explosive instability in the three-wave interaction
Authors: Augusteijn Marijke F.
Published: February 2003

We consider the interaction between three waves in a dissipation-free medium which carry positive and negative energy. There exist both bounded oscillatory and unbounded explosive solutions when the frequency mismatch is nonzero. The type of solutions found for given initial conditions depends in part on the number of relevant roots of a certain polynomial. Here it is shown how this can be used to obtain a sufficient condition for explosive instability in terms of the constants of the Manley-Rowe relations.
Optical studies on hopping-transport mechanism of excess electrons in liquefied nitrogen
Authors: Murooka Y. , Hirashima Y. , Kubo M.
Published: February 2003

Hopping conduction in liquefied nitrogen is investigated using a modified optical Schlieren system. The mobility of the electronic charge carriers is found to lie in the range 0.14–0.60 cm2/V sec. These values are two or three orders of magnitude larger than that of negative ions (10−4–10−3 cm2/V sec) and also two or three orders smaller than the predictable maximum value of free electrons 102–103 cm2/V sec in liquefied nitrogen. The results suggest that electrons emitted from the cathode move by a hopping-transport mechanism, such as the polaron- and a quantum-tunneling-type conduction. The sensitivity of the present optical Schlieren system was measured by a Mach Zehnder technique, and the observable change of the refractive index is greater than 2×10−5.
Transport of broadening charge packets at surfaces
Authors: Nelson D. F.
Published: February 2003

Surface transport of charge packets in metal-oxide-semiconductor structures is studied theoretically. The governing nonlinear partial differential equation is derived, and an approximate analytical solution to it is found. It shows that the density in the packet approximates an inverted truncated parabola whose width increases as the cube root of time, and whose drift velocity has a time dependence determined by the self-generated and applied electric fields normal to the surface. The time average of the self-generated and applied normal fields is shown to result in averages of the two fields over different portions of the drift channel. The flux peak velocity, which is measured in a time-of-flight experiment, is shown to be the sought-after drift velocity of the density peak plus the (negative) velocity of the flux peak relative to the density peak. An expression for the latter quantity is developed. A relation between the flux peak velocity and the drift velocity at the flux peak is also derived.
Plasma-hydrogenation effects on conductivity and electron spin resonance in undoped polycrystalline silicon
Authors: Hasegawa S. , Takenaka S. , Kurata Y.
Published: February 2003

The effect of plasma-hydrogenation on the electrical properties and electron spin resonance (ESR) are investigated for undoped polycrystalline silicon films produced by annealing from chemical vapor deposited amorphous silicon. The conduction type for all samples used is p-type. Under a constant plasma annealing temperature, a maximum of the dark conductivity and a minimum of its activation energy are observed at a certain annealing time. This result suggests the presence of two stages in the process of hydrogenation, which is not explained by the models proposed up to now. The ESR spin density decreases and the photoconductivity increases with plasma annealing time, and both are saturated at the first stage. A model for the carrier transport mechanism is proposed in which crystallites with surface bandbending and a damaged layer between the crystallites are included, and the variations of the dark conductivity and photoconductivity are attributed to surface conduction of crystallites and limitation at the damaged layer, respectively, depending on the density of localized states. The temperature dependence of the dark conductivity is also discussed based on this model.
Post-hydrogenated chemical vapor deposited amorphous silicon Schottky diodes
Authors: Szydlo N. , Magariño J. , Kaplan D.
Published: February 2003

Amorphous Si Schottky diodes are prepared by chemical vapor deposition and a post- hydrogenation treatment. Capacitance and photocurrent measurements on these diodes as a function of doping are discussed in terms of space-charge characteristics and carrier collection mechanisms. For doped samples a full analysis of the C(ω) and C(V) dependences enables us to obtain the space-charge width and the doping efficiency. A correlation between space-charge width and collection length of photogenerated carriers is obtained in these samples. For undoped diodes the photocurrent versus wavelength dependences are used to analyze the collection efficiency. A power efficiency of 2.5% is obtained for a fully depleted cell without antireflection coating under AMl solar simulator conditions.
Stray magnetic coupling between neighboring superconducting memory cells in dense arrays of Josephson interferometers
Authors: Jaeckel H. , Moore D. F.
Published: February 2003

Experimental measurements of the coupling between neighboring single-flux-quantum cells are compared with numerical calculations made using a two-dimensional model of the structure. Good agreement is found both for the influence of a control current in one cell on the neighboring cells, and for the effect of the stray field due to a stored flux quantum. The magnitudes of these unwanted effects between memory cells having the bridge-type interferometer structure are calculated as the minimum linewidth is reduced, and the limits to miniaturization imposed by stray magnetic coupling are estimated.
The determination of grain-boundary recombination rates by scanned spot excitation methods
Authors: Seager C. H.
Published: February 2003

Laser- and electron-beam induced-current techniques have been used to determine minority carrier diffusion lengths and grain-boundary recombination velocities in polycrystalline silicon. Data obtained on a variety of grain boundaries appear to be in good agreement with the recent calculations by Zook.
Surface profile measurement using the confocal microscope
Authors: Hamilton D. K. , Wilson T.
Published: February 2003

A novel high-resolution non-contacting optical method of surface profile measurement is described and typical results presented. The method utilizes the depth discrimination properties of the nonfocal scanning optical microscope.
Photoluminescence studies on the layer semiconductor InSe
Authors: Abha  , Warrier A. V. R.
Published: February 2003

Laser excited photoluminescence of InSe single crystal shows three peaks at 1.311, 1.272, and 1.227 eV. The relative intensity of these peaks variation from point to point on the surface of the crystal. The high-energy peak is assigned to impurity to band transitions, the 1.277 eV to donor-acceptor type transition and 1.227 eV to transition within an impurity vacancy complex. From these peak positions and the known band gap, the donor and acceptor levels associated with these centers are estimated to be approximately 41 and 40 meV, respectively.
The origin of the 1.59-eV luminescence in ZnTe and the nature of the postrange defects from ion implantation
Authors: Norris C. B.
Published: February 2003

We describe constituent-vapor heat-treatment experiments on ZnTe which indicate that the 1.59- eV luminescence in this material is VZn -related. The effects of Ga or I doping suggest further that the band is associated with some species of VZn -donor complex. This understanding of the 1.59- eV luminescence provides additional insight into our earlier study of postrange-defect introduction in ion-implanted ZnTe. The observed survival of the incumbent 1.59-eV band in the postrange zone is discussed in relation to the conclusion from earlier published studies that Zni are the dominant postrange defects in ZnTe. We conclude that Zni are not strongly involved in the observed postrange damage. To the contrary, our work gives some indication that VZn - and/or VTe -related centers are formed in the postrange zone.
Light-activated electroluminescent switch with an active feedback circuit
Authors: Campbell J. C. , Qua G. J. , Copeland J. A. , Dentai A. G.
Published: February 2003

We describe an electroluminescent InP/InGaAsP p-n-p-n switch which can be optically activated. The high sensitivity exhibited by these devices eases the restriction of precise control of the bias voltage. Automatic resetting from the high-current ’’on’’ state to the initial ’’off’’ state is achieved with an active feedback circuit which utilizes a complementary metal-oxide semiconductor (CMOS) NAND gate and a monostable multivibrator. The best rise and fall times that we have observed are both about 150 ns. The recovery time is limited to approximately 600 ns by the fall time of the monostable multivibrator.
Laser heating in thermoluminescence dosimetry
Authors: Gasiot J. , Bräunlich P. , Fillard J. P.
Published: February 2003

Thermoluminescence (TL) glow curves have been obtained from γ-irradiated commercial dosimetry materials (LiF:Mg, Ti; CaSO4:Mn; CaSO4:Dy; CaF2:Dy; Li2B4O7) with a novel laser heating technique. It utilizes short (10–1000 ms) pulses from a CO2 laser of 1–8 W power focused to about 1-mm diam spot sizes onto thin (<100 μm) layers of powder precipitated on microscope cover slides. In some cases these powder layers were spray coated with a thin film of conventional high temperature polymers. These acted both as a binder to stabilize the powder as well as to enhance the heat transfer from the laser beam to those TL materials which have a small absorption coefficient for 10.6 μm photons (e.g., LiF and CaF2). Heating rates in excess of 104 K s−1 have been observed without noticeable decrease in the TL emission efficiency. Laser heating is, thus, shown to be a promising technique to increase the signal-to-noise ratio of TL emission signals. As a result, true microdosimetry in the mR range could be demonstrated with samples of less than 20 μg. Applications to remote in situ TL microdosimetry can now be anticipated as well as sensitive high resolution TL imaging of spatial exposure distributions.
On the emission of electrons from solid H2 and D2 by bombardment with 1–3-keV electrons up to very large angles of incidence
Authors: So/rensen H. , Schou J.
Published: February 2003

Electron emission, i.e., electron reflection (ER) and secondary electron emission (SEE), was studied for solid H2 and D2 for oblique incidence of 1–3 keV electrons up to an angle of incidence ϑ of 83°. The ER coefficient η was small at low angles, and rose rapidly with increasing ϑ above 60– 65°. Only at large angles and low energies were the results different for H2 and D2, those for H2 being the lower ones. The angular variation of the SEE coefficient δ may be written as δ(ϑ) = δ(0)(cos ϑ)−3/2 up to an angle of 65–75°. For H2 the SEE coefficient is around 0.65 times that for D2 except at the largest angles. The results agree well with the existing qualitative tendencies described in the literature. The variation with the angle of incidence shows a fair agreement with an estimate based on data for the angular distribution of electrons ejected from ionized hydrogen molecules. In addition, an ionization cascade treatment leads to an expression for the behavior of the yield of those secondary electrons that are generated directly by the primaries. The agreement with experimental data is good.
Transmission electron microscope study of ion and electron beam induced structural changes in a-Ge0.25 Se0.75 inorganic resist thin films
Authors: Balasubramanyam K. , Chen L. J. , Ruoff A. L. , Wolf E. D.
Published: February 2003

The ion and electron beam effects in polycrystalline phases of Ag2Se and its oxides produced by electroless deposition on a-Ge0.25 Se0.75 thin film (negative inorganic resist) surface were investigated by transmission electron microscopy and microprobe analysis. The disappearance of a few polycrystalline rings corresponding to Ag2Se and growth of needles of 300–5000 nm length and 7–50 nm width were observed when the resist was exposed to an ion dose which is less than the lithographic sensitivity of this inorganic resist. Interestingly, no needle growth was observed either in electron beam irradiated a-Ge0.25 Se0.75 films, or in ion beam exposed as deposited a- Ge0.25 Se0.75 films (positive resist).
Determination of optimum load for a solar cell
Authors: Kothari L. S. , Mathur P. C. , Kapoor Avinashi , Saxena P. , Sharma R. P.
Published: February 2003

An expression for load for maximum power transfer from a real solar cell, having resistive and current leakage losses, has been obtained using Lagrange’s method of undetermined multipliers for solving the transcendental current-voltage relationship. The theoretical results are compared with the experimental measurements of the optimum load for p-n junction solar cells for various illumination levels.
Effects of stoichiometry on thermal stability of undoped, semi-insulating GaAs
Authors: Ta L. B. , Hobgood H. M. , Rohatgi A. , Thomas R. N.
Published: February 2003

We provide independent evidence of the effects of melt composition on the semi-insulating behavior and thermal stability of undoped GaAs crystals pulled from pyrolytic boron nitride crucibles by the liquid-encapsulated Czochralski technique. Semi-insulating crystals pulled from stoichiometric or As-rich melts show excellent stability to heat treatments, in contrast to semi- insulating Ga-rich material which exhibits p-type conversion after prolonged annealing at 860 °C. Deep level transient spectroscopy and Hall-effect measurements suggest that p-conversion is caused by outdiffusion of native As and/or Ga defects associated with the EL2 deep donors, resulting in uncompensated residual acceptors, predominantly carbon impurities at the surface. The measured mobility of undoped, semi-insulating GaAs is found empirically to be a sensitive parameter for qualifying substrates for direct ion implantation.
Barrier heights of sputter deposited Fe contacts to n and p silicon
Authors: Koshy J.
Published: February 2003

Measurements of hole and electron barriers of junctions between sputter deposited Fe films and either p-Si or n-Si are reported. The barrier heights were determined from forward IV characteristics. The barrier heights depend on the sputtering power used to deposit the Fe films. Annealing the contacts resulted in a decrease in the hole barrier and an increase in the electron barrier.
Rutherford backscattering analysis of electroless gold contacts on cadmium telluride
Authors: Mancini A. M. , Quirini A. , Vasanelli L. , Perillo E. , Rosato E. , Spadaccini G. , Barbarino E.
Published: February 2003

In order to clarify the physical properties of electroless gold contacts on CdTe crystals, Rutherford backscattering measurements have been performed using a 4-MeV 4He beam. Backscattering spectra show that a sharp gold film grows on the crystal surface and that a strong chemical reaction takes place between the substrate and the gold chloride solution used for the electroless Au deposition. Depth profile analyses, supported by Auger spectroscopy results, confirm that the Au-CdTe interface region becomes significantly lower in cadmium atom concentration. This feature can probably explain the electrical behavior of such gold contacts (ohmic on p type and rectifying on n-type CdTe).
Néel walls and line transitions in a (100) garnet film
Authors: Kryder M. H. , Gallagher T. J. , Scranton R. A.
Published: February 2003

An investigation was made of novel domain wall structures in (100) SmTmCaGe garnet films. These (100) oriented films have strong in-plane anisotropy resulting in the formation of Néel type domain walls in spite of the large thickness (∼1 μm) of the films. The dipolar nature of these walls was detected by use of a modified Bitter technique in which a bias field polarized the magnetic particles perpendicular to the film plane. Line transitions separating antiparallel domain wall segments were observed to move along the walls when appropriate polarity in-plane fields were applied. These line transitions are analogous to the Bloch point and crosstie observed in NiFe films. In the garnet films, however, anisotropy is stronger, and because the magnetization is much weaker, the crosstie does not form. Theoretical considerations suggest that the Néel wall has a width of about 1500 Å and that alternate line transitions, having different magnetization configurations, are nearly identical in width (∼600 Å) and energy. Furthermore, since the magnetization is low, there is little interaction between line transitions and they may be relatively densely packed along the Néel wall.
Dielectric heating
Authors: Ross David
Published: February 2003

The time-averaged Joule heat power absorption density dissipated by a dielectric slab under electromagnetic illumination, at perpendicular and parallel polarizations, is calculated as a function fo the material’s complex dielectric constant and magnetic permeability, and the time-averaged energy density, incidence angle, and frequency of the incident beam. The material ca be in free space or metal backed. As an application, the steady-state temperature gradient for a metal-backed sample in a 23° environment is also derived. These algebraic expressions can be programmed into a computer to predict how candidate samples will perform under high intensity illumiation.
Electrical breakdown of aluminum oxide films flanked by metallic electrodes
Authors: Klein N. , Albert M.
Published: February 2003

Breakdown characteristics of anodically grown aluminum oxide films were determined in the range of temperature 4.2–354 K, of thickness 47–187 nm, on change of polarity and for gold and aluminum electrodes. Results could be consistently interpreted with the theory of breakdown due to impact ionization by one type of carrier, presented in the prior paper. The theory ascribes breakdown events to the complex interaction of impact ionization, electron injection, hole trapping, and drift and electron trapping. The effect of trapping was found to be of primary importance, since changes in trapping properties can greatly alter the breakdown properties of aluminum oxide. The wide range of breakdown observations from 3 to 13 MV/cm was explained with changes in trapped electron charge and possibly with change in impact ionization processes, trap to band at low fields, but band to band transitions at high fields. Anomalous breakdown characteristics demonstrate that a trapped electron charge can produce protection from breakdown and that trapped electron densities can be in the low 1018/cm3 up to fields of 10 MV/cm.
Infrared studies of isothermal annealing of ion-implanted silicon: Refractive indices, regrowth rates, and carrier profiles
Authors: Waddell C. N. , Spitzer W. G. , Hubler G. K. , Fredrickson J. E.
Published: February 2003

A model-dependent computer analysis technique developed previously has in this work been applied to the infrared reflection data of a number of 〈111〉 and 〈100〉 oriented Si samples which were implanted with high fluences of Si or P ions and then taken through an isothermal annealing process. The physical properties deduced from this analysis are: (i) Dielectric properties including the frequency dependent refractive indices of the recrystallized Si and of the a-Si as a function of annealing temperature and time; (ii) structural information including the amorphous layer depth, widths of transition regions, the epitaxial regrowth rates; and (iii) electrical properties including the depth profile of the carrier density, the carrier mobility near the maximum carrier density, and the carrier activation efficiency. The physical interpretation of the results is discussed and, where possible, comparisons with results of other experiments are made.
Refractive indices of III–V compounds: Key properties of InGaAsP relevant to device design
Authors: Adachi Sadao
Published: February 2003

A method for calculation of refractive indices in III–V compounds at energies below the direct band edge is presented. Spectral dependence of the refractive-index data is analyzed on the basis of simplified models of the interband transitions. The theoretical prediction shows a quite good agreement with the experimental data of III–V binaries. This model is also applied to InGaAsP quaternaries lattice matched to InP. The refractive-index steps between InGaAsP and InP are obtained for a variety of waveguiding device applications.
Growth of eutectic thin film structures
Authors: Cline H. E.
Published: February 2003

A nonlinear model of eutectic growth yields the shape of the irregular interface in which the triple points are displaced both parallel and perpendicular to the interface. The spacing of the eutectic film is controlled by the formation of faults below a critical spacing and by catastrophic breakdown in the interface shape at larger spacings. The stable growth range decreases with increasing perturbation amplitude. Local regions of large spacing that originate from defects in the eutectic thin film, produce a wave of bent plates which with time eliminate the initial spacing variation. Simulated microstructures derived from this model correspond to structures of directionally solidified eutectic thin films. The mechanics of eutectic thin film growth arediscussed.
Carbon tetrachloride plasma etching of GaAs and InP: A kinetic study utilizing nonperturbative optical techniques
Authors: Gottscho Richard A. , Smolinsky Gerald , Burton Randolph H.
Published: February 2003

CCl4 plasma etching rates of GaAs and InP as a function of substrate temperature, rf power (at 55 kHz), reactor loading, flow, and time are reported. The etching-rate dependence on temperature from 165 to 425 °C is non-Arrhenius. Time-dependent etching-rate data were obtained from In and InCl plasma emission after establishing an empirical proportionality between emission intensity and etching rate. Indium ground state concentration, as measured by laser-induced fluorescence, was found to exhibit the same time dependence as In and InCl plasma emission. For GaAs and InP (above 250 °C), etching reactions are shown to be limited by product and/or reactant diffusion through a passive chlorocarbon film. For InP below 250 °C, time-dependent etching-rate data suggest that this deposited film interacts with InP substrates so as to enhance the etching rate.
Current and magnetic field penetration into a plasma: Application to high power-density flow in transmission lines
Authors: Baker Louis
Published: February 2003

When a material is heated sufficiently to cause a conducting plasma to blow off, the resulting layer shields this material from magnetic fields and currents that may be present. Theoretical considerations relevant to the simulation of such situations are discussed. Results are presented for the problem of current flow in transmission lines undergoing surface blowoff due to high current densities. For a typical case of interest only 10% of the current is found to flow in the plasma blowoff. Moreover, the transmission-line properties are not substantially changed on time scales of interest.
Ion channeling in GaAs: Be, Mg, Zn, and Cd, and calculations of electronic stopping powers
Authors: Wilson R. G.
Published: February 2003

Atom depth distributions measured by secondary ion mass spectrometry are reported for 9Be, 24Mg, 64Zn, and 114Cd channeled in the GaAs crystal. The ion energies were 150 or 300 keV and the fluences were 3.0×1013 cm−2. Fairly well-defined maximum ranges are observed in the 〈110〉 profiles for three of these four acceptor impurities in GaAs. The Mg and Zn profiles are deep because of the low electronic stopping and no peak is observed in the deep channeled region of the profiles. The 〈110〉 Be profile is flat within a factor of about two over most of the range, but the deep portion is rounded and does not decrease sharply at the maximum range as it does for Si, S, Se, Cd, and Te. These data are combined with those reported previously for Si, S, Se, and Te, and the maximum ranges in the 〈110〉 and 〈100〉 channeling orientations are used to calculate values of the electronic stopping Se and the coefficient k, based on the assumption of velocity- proportional electronic stopping (Se = kE0.50).
Diffusion in intermetallic compounds with the CaF2 structure: A marker study of the formation of NiSi2 thin films
Authors: d’Heurle F. , Petersson S. , Stolt L. , Strizker B.
Published: February 2003

A xenon marker was implanted into a thin film of NiSi initially formed on its silicon substrate by the reaction of this substrate with a thin film of nickel. During the subsequent transformation of NiSi into NiSi2 at about 800 °C, the displacement of the xenon marker towards the free surface of the film indicates that nickel constitutes the main diffusive species for the growth of NiSi2. This is compared with the previously published knowledge about Ni2Si, NiSi, and the silicides of cobalt.
Diffusion controlled ledge growth in a medium of finite extent
Authors: Atkinson C.
Published: February 2003

Steady ledge motion during lateral growth in solid-solid phase transformations is examined in an untransformed matrix of finite lateral extent. It is assumed that volume diffusion in the parent phase is the predominant contribution to the growth rate. Results are presented for the step speed (Peclet number) as a function of the lateral extent of the untransformed parent phase for a given dimensionless normalized supersaturation. One striking result is that this steady step speed tends to zero when the ratio of the remaining thickness of untransformed matrix to the step height is equal to 1/Ω0 where Ω0 = (c∞−ce)/(cp−ce) is the normalized supersaturation. cp is the solute concentration of the precipitate, ce the equilibrium solute concentration in the matrix at the precipitate matrix interface and c∞ the initial concentration of the untransformed matrix.
Characterization of NbSi2 thin films
Authors: Rude Curtiss D. , Chow T. Paul , Steckl Andrew J.
Published: February 2003

The physical and electrical properties of niobium silicide thin films are studied. These films were rf sputtered from an alloy target of stoichiometric proportion onto oxidized silicon substrates at 350 °C to improve film adhesion. Structural and compositional properties of as-sputtered and heat-treated films were studied by x-ray diffraction, Auger electron spectroscopy, Rutherford backscattering spectroscopy, and secondary ion mass spectrometry. Films annealed in H2 or N2 were found to consist of mainly NbSi2 with Nb5Si3 as a significant component. The resistivity of these films decreases by a factor of 2 upon annealing to ∼1×10−4 Ω cm. Heat treatment in O2 resulted in insulating films. The composition of the oxidized films was shown by both x-ray and RBS analysis to consist of Nb2O5 and SiOx. NbSi2-gate metal-oxide-semiconductor capacitors were fabricated on both n-type and p-type Si substrates. The work function of NbSi2, determined from C-V measurements, was found to be 4.5 and 4.3 V for n-type and p-type substrates, respectively. Temperature-bias stress measurements resulted only in minor shifts in the flatband voltage, typically 0.1 V.
Influence of carbon and oxygen on donor formation at 700 °C in Czochralski-grown silicon
Authors: Ohsawa Akira , Takizawa Ritsuo , Honda Kouichirou , Shibatomi Akihiro , Ohkawa Shinzi
Published: February 2003

Influence of oxygen and carbon on donor formation by annealing at 700 °C was studied by infrared absorption, resistivity, and spreading resistance measurements in Czochralski-grown silicon. Donor concentration correlates with both oxygen and carbon reductions by the annealing at 700 °C. Donor distribution corresponds to etch pit distribution observed after the annealing. The donor is proposed to be oxygen precipitate nucleated at carbon site. The influence of the donor generation on the device parameter in metal-oxide- silicon memory field-effect transistors is discussed.
Time domain photoacoustic relaxation measurements: Vibrational energy transfer for HD in v = 4, 5, and 6
Authors: Rohlfing Eric A. , Gelfand Jack , Miles Richard B.
Published: February 2003

Details of the experimental measurement of collisional relaxation from the upper vibrational states of HD are presented. Direct overtone pumping of HD in v = 4,5, and 6 was accomplished with a pulsed visible wavelength dye laser. The change in translational energy due to collisional relaxation is measured as a function of time by a sensitive pressure transducer placed at the cell wall. Data for vibrational relaxation in pure HD and in HD:4He mixtures are presented.
On hyperfine frequency shifts caused by buffer gases: Application to the optically pumped passive rubidium frequency standard
Authors: Vanier J. , Kunski R. , Cyr N. , Savard J. Y. , Têtu M.
Published: February 2003

Experiments are reported on the effect of buffer gases on the hyperfine frequency of rubidium 87 as used in passive rubidium frequency standards. In some mixtures of buffer gases a strong quadratic dependence of the frequency on temperature is observed. The data are explained by means of a phenomenological approach and with the help of data published previously on pure buffer gases. A comment is made on an article which appears to lead to doubtful conclusions.
A generalized model of photothermal radiometry
Authors: Tom Roderick D. , O’Hara Ellen P. , Benin David
Published: February 2003

The theory of photothermal radiometry is extended here to include samples which are nonopaque to thermal radiation. Under certain assumptions, analytical expressions relating the detected signal to the thermal and optical properties of the sample are derived for sinusoidal modulation of the incident light intensity. Cases where the sample is a weak infrared absorber and cases of high modulation frequency can now be considered.
Theoretical and experimental studies of electron deposition in thin targets
Authors: Peugnet C. , Bailly-Salins R. , Devin A. , Duborgel B. , Gouard Ph. , Fedotoff M.
Published: February 2003

Experiments performed on the Chanteclair accelerator to study the relativistic electron beam absorption in high and low Z thin foils are discussed. The relativistic electron beam-target interaction is simulated with a trajec code coupled to a hydrodynamic code. Simulations of high current thin gold foil heating experiments led to an energy deposition enhancement of about 2–3, with a rear side temperature of 15–20 eV, in agreement with experimental data. In low current experiments with low Z targets, no anomalous deposition was observed.
Absolute experimental cross sections for the electron impact single, double, triple, and quadruple ionization of Cs+ ions
Authors: Hertling D. R. , Feeney R. K. , Hughes D. W. , Sayle II W. E.
Published: February 2003

Absolute cross sections for the single, double, triple, and quadruple ionization of Cs+ ions by electron impact have been measured from below their respective thresholds to approximately 5000 eV. These measurements have been made using a crossed beam facility operated in a pulsed beam mode. Numerous consistency checks were performed in order to identify and evaluate possible sources of experimental error.
A diagnostic for intense focused proton beams using the 11B (p,α)2α reaction
Authors: Miyamoto S. , Ozaki T. , Imasaki K. , Higaki S. , Nakai S. , Yamanaka C.
Published: February 2003

A new diagnostic method for intense focused proton beams is described. The measurement is made by detecting α particles which are emitted simultaneously from 11B( p,α)2α nuclear reactions in a baron nitride target. This diagnostic can be used at high current densities without the complication of flux attenuators.