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Journal of Applied Physics

Issue 6 • Date Mar 1989

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Displaying Results 1 - 25 of 68
  • Measurement of pulse lengthening with pulse energy increase in picosecond Nd:YAG laser pulses

    Page(s): 2187 - 2190
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    Taking advantage of a new technique, we have monitored the relative variations of time duration and mode size as a function of the pulse energy for 30‐ps‐long Nd:YAG laser pulses. In particular, by carrying out a statistical analysis, we have observed that the pulse time duration is an increasing function of the pulse energy, according to the theoretical modeling of passively mode‐locked lasers. The measurements can be easily extended to the femtosecond regime. View full abstract»

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  • Volume holographic interconnections with maximal capacity and minimal cross talk

    Page(s): 2191 - 2194
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    Optical interconnections utilizing volume holography are described. Intrinsic cross‐talk effects that limit the number of independent interconnections are identified and analyzed by applying coupled‐wave analysis. Sampling grids for removing the first‐order cross talk are presented, resulting in a system limited by second‐ and third‐order cross talk only. View full abstract»

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  • Light scattering by air heated from an aerosol due to pulsed irradiation

    Page(s): 2195 - 2198
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    The problem of the scattering by air which has been locally heated by aerosols irradiated by a short pulse, for example, by a pulsed laser, is addressed through the use of the heat conduction equation and scattering theory. The resulting air scattering cross section increases as with the square of the absorbed fluence. After a pulse, it increases to a maximum and then decays as the inverse of time. For absorbed fluences greater than 2 J/cm2, the air scattering cross section can exceed that of the aerosol itself. For multiple irradiation pulses, the air scattering cross section reaches a maximum asymptotic limit. For an aerosol cloud, the air scattering cross section decays exponentially after the thermal wave from an aerosol reaches one‐third of the interparticle spacing. View full abstract»

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  • Experimental study of the ionization front in pulsed‐surface‐wave‐produced plasmas

    Page(s): 2199 - 2204
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    The advance of the ionization front along the plasma column is studied during the formation process of plasmas produced by a surface wave. The experimental measurements have been performed in argon gas, for the 0.1–30‐Torr pressure range, using pulsed microwave power at 2.45 GHz. The ionization front velocity decreases along the plasma column, from its maximum value at the launcher to the zero value at the stationary plasma column end, similarly to the surface‐wave power diminution. This velocity can be expressed to depend only on the product collision frequency times tube radius and the surface‐wave incident power along the plasma column. View full abstract»

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  • Observation of sheath structure near a rf electrode in a magnetized afterglow plasma

    Page(s): 2205 - 2208
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    The sheath structure near a rf electrode has been observed by measuring the spatial profiles of the potential and density in a magnetized afterglow plasma. Dependence of the structure on the rf frequency (10–40 MHz) and elapsed time during the afterglow in a periodic, pulsed rf discharge operation are obtained by a time resolved measuring method. The potential close to the electrode is found to increase with increasing frequency and with elapsed afterglow time, without much change of the density profile. In addition, a slight decrease of the electron temperature has been observed during the afterglow time, although the density is roughly constant. View full abstract»

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  • Raman scattering study of carrier activation in zinc‐ and silicon‐implanted and pulse‐laser‐annealed GaAs

    Page(s): 2209 - 2213
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    This study reports the plasmon‐LO‐phonon coupled modes observed in the Raman spectra of GaAs implanted with p‐type (zinc) and n‐type (silicon) implants and then pulse laser annealed. The coupled modes are due to the interaction between LO phonon and free carriers and this allows a rough estimation of the carrier concentration from the frequency and width of the L- coupled modes. The wavelength dependence for λ=1.06 and 0.53 μm of the threshold power density for the best carrier activation is reported here. The width of the depletion layer is estimated in silicon implanted samples for various power densities of 22, 26, and 31 MW/cm.2 View full abstract»

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  • The structure of Cu3Au above the critical temperature

    Page(s): 2214 - 2219
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    The diffuse x‐ray scattering intensity from a single crystal of Cu3Au was measured in a volume of reciprocal space at a temperature of 703 K, approximately 35 K above the transition temperature for ordering in this alloy. Intensity was measured in absolute units and was separated into components due to short‐range order (SRO) and atomic displacements. The SRO parameters determined agree qualitatively with previous experimenters but agree best in magnitude with the original study by Cowley [J. Appl. Phys. 21, 24 (1950)]. Computer simulations of the structure, based on the SRO parameters, show that atoms with ordered environments tend to cluster into small domains that have dimensions of 1–10 unit cells in length and are surrounded by a disordered matrix. The average displacements of near‐neighbor pairs were found to be contrary to what has previously been assumed: Au‐Au neighbors were found to have negative displacements on average and Au‐Cu pairs positive displacements, compared to the average interatomic displacements. View full abstract»

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  • Nucleation mechanisms and the elimination of misfit dislocations at mismatched interfaces by reduction in growth area

    Page(s): 2220 - 2237
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    To investigate the effect of growth area on interface dislocation density in strained‐layer epitaxy, we have fabricated 2‐μm‐high mesas of varying lateral dimensions and geometry in (001) GaAs substrates with dislocation densities of 1.5×105, 104, and 102 cm-2. 3500‐, 7000‐, and 8250‐Å‐thick In0.05Ga0.95As layers, corresponding to 5, 10, and 11 times the experimental critical layer thickness as measured for large‐area samples, were then deposited by molecular‐beam epitaxy. For the 3500‐Å layers, the linear interface dislocation density, defined as the inverse of the average dislocation spacing, was reduced from greater than 5000 to less than 800 cm-1 for mesas as large as 100 μm. A pronounced difference in the linear interface dislocation densities along the two interface 〈110〉 directions indicates that α dislocations nucleate about twice as much as β dislocations. For samples grown on the highest dislocation density substrates, the linear interface‐dislocation density was found to vary linearly with mesa width and to extrapolate to a zero linear interface‐dislocation density for a mesa width of zero. This behavior excludes dislocation multiplication or the nucleation of surface half‐loops as operative nucleation sources for misfit dislocations in these layers. Only nucleation sources that scale with area (termed fixed sources) are active. In specimens with lower substrate dislocation densities, the density of interface dislocations still varies linearly with mesa size, but the slope becomes independent of substrate dislocation density, indicating that surface inhomogeneities now act as the dominant source for misfit dislocations. Thus, in 3500‐Å‐thick overlayers, substrate dislocatio- ns and substrate inhomogeneities are the active fixed nucleation sources. Since only fixed nucleation sources are active, a single strained layer will dramatically reduce the threading dislocation density in the epilayer. For the 7000‐Å layers, we observe a superlinear increase in linear interface‐dislocation density with mesa size for mesas greater than 200 μm, indicating that dislocation multiplication occurs in large mesas. For mesas less than 200 μm in width, linear interface‐dislocation density decreases linearly with mesa size, but extrapolates to a nonzero linear interface‐dislocation density for a mesa size of zero. This nonzero extrapolation suggests an additional active source which generates a dislocation density that cannot be decreased to zero by decreasing the mesa size. Cathodoluminescence (CL) images using radiative recombination indicate that the additional source is nucleation from the mesa edges. Despite a doubling in epilayer thickness from 3500 to 7000 Å, the linear interface‐dislocation density for mesas 100 μm in width is still very low, approximately 1500 cm-1. The 8250‐Å layers possess interface‐dislocation densities too high to be accurately determined with CL. However, increases in CL intensity as mesa width is reduced indicate that the interface‐dislocation density is decreasing and that growth on small areas produces higher‐quality layers than growth on large areas. Our investigations show that different sources for misfit dislocations become active at different epilayer strain levels. The critical thickness depends on which type of nucleation source becomes activated first; therefore, different critical thicknesses can be observed depending on which kind of source is present in a specimen. View full abstract»

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  • Three‐dimensional solid‐phase‐epitaxial regrowth from As+‐implanted Si

    Page(s): 2238 - 2242
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    Solid‐phase‐epitaxial (SPE) regrowth from selectively As+‐implanted amorphous Si is analyzed by cross‐sectional transmission electron microscopy. SPE regrowth in the (100) wafers proceeds into both vertical and lateral directions simultaneously. For (111) samples, SPE regrowth in the diagonal direction, i.e., 〈100〉 direction near the mask edge, is dominant. In addition to the end of range defects and projected range defects, in the SPE process, defects of a third type are generated just beneath the implantation mask edge. Differences in mask material which control the applied stress at the mask edge have little influence on edge defect generation. Substrate orientation and mask pattern direction play important roles in the edge defect formation mechanism. View full abstract»

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  • Nonequilibrium behavior of charged point defects during phosphorus diffusion in silicon

    Page(s): 2243 - 2247
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    A new nonequilibrium kinetic model for phosphorus diffusion in silicon is presented. Concentrations of charged defects and defect‐impurity pairs are determined explicitly by solving a system of quasilinear evolution equations, each of a drift‐diffusion‐reaction form with constant diffusivities. This formulation subsumes a hierarchy of models from the literature. Calculated profiles for a 10‐min predeposition show both a tail and a well‐defined kink plateau. The latter results directly from the kinetic model under the assumption of a strong bimolecular recombination. View full abstract»

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  • Photoluminescence study of the annealing behavior of transmuted impurities in neutron‐transmutation‐doped semi‐insulating GaAs

    Page(s): 2248 - 2253
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    In neutron‐transmutation‐doped GaAs irradiated with various fast neutron fluences, the annealing behavior of band‐germanium acceptor [Ge(B‐A)] transitions has been evaluated using the photoluminescence technique. In the fast neutron irradiation of ≤7.0×1017 cm-2, a few percent of transmuted Ge atoms behave as acceptors in As sites and more than 98% of the transmuted Ge atoms activate as donors in Ga sites. In the fast neutron irradiation of 3.7×1018 cm-2, the shift of Ge(B‐A) transitions towards lower energies originates from the band‐edge distortion. Removing the band‐edge distortion by annealing above 790 °C leads to the increase in the Ge acceptor, accompanied by an increase of the peak intensity of Ge(B‐A) transitions. The lower electrical activation of transmuted impurities (∼75%) arises from the high‐temperature annealing required to remove the radiation damage. On annealing out the radiation damage, the peak shift of Ge(B‐A) transitions based on the increase in the free carrier is discussed using the Burstein–Moss model. View full abstract»

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  • Defect‐ordered phases in a multiphase Cu‐In‐Se material

    Page(s): 2254 - 2257
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    Several copper‐deficient phases in a Cu‐In‐Se ingot were identified and characterized by electron diffraction and energy dispersive x‐ray analysis. Some were phases already identified by x ray and electron diffraction. A new vacancy‐ordered phase with composition close to Cu0.75In2.25Se4 was identified to have a thiogallate‐type structure. A phase with composition close to CuIn5Se8 exhibited a polytype structure with both 7‐ and 14‐layer stacking sequences. View full abstract»

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  • Energy deposition of keV electrons in light elements

    Page(s): 2258 - 2266
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    The Monte Carlo simulation method has been used to investigate the spatial distribution of deposited energy for 1–10 keV electrons incident on solid hydrogen, nitrogen, neon, silicon, aluminum, and argon. In the simulation, elastic scattering cross sections are calculated exactly using the single‐atom crystalline potentials. Inelastic energy loss processes for hydrogen are based on the ionization cross section from Green and Sawada [J. Atmos. Terr. Phys. 34, 1719 (1972)] and the gas‐phase stopping power from Parks et al. [Nucl. Fus. 17, 539 (1977)]. For the heavier materials a modification of Gryziński’s [Phys. Rev. A 138, 305 (1965); 138, 322 (1965); 138, 336 (1965)] semiempirical expression for each core and valence electron excitation is used. The energy‐deposition distribution of keV electrons and the ionization distribution of weakly bound electrons are practically equal, whereas the penetration depth distribution extends deeper into the material than the energy‐deposition distribution. The energy‐deposition distributions of keV electrons for light materials, except for hydrogen, can be represented quite well by a universal distribution. In addition, accurate Gaussian approximations for the different materials in the entire energy region from 1 to 10 keV have been evaluated. Parameters such as the mean penetration depth and the mean energy‐deposition depth are included as well. View full abstract»

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  • Relaxation and rocking‐curve broadening of strained (Ga,In)As single layers on (001) GaAs

    Page(s): 2267 - 2271
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    We have measured the lattice relaxation of various strained Ga1-xInxAs layers which are thicker than the equilibrium critical thickness. Samples with a thickness near the energy balance model critical thickness exhibited a large relaxation. We have analyzed the strain relaxation data in a GaInAs/GaAs system using the Dodson–Tsao plastic flow model [Appl. Phys. Lett. 52, 852 (1988)]. It was found that the model provides a reasonably good fit to the data, however, the model parameters have widely different values for the GaInAs/GaAs samples with different mismatches. One parameter of the model shows an approximate inverse‐square‐law dependence on the misfit. The rocking‐curve linewidths are presented for the GaInAs layers. The measured linewidths are discussed in terms of the theoretical linewidth, dynamical x‐ray diffraction, and defect density depth distribution. View full abstract»

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  • Interstitial Li doping of a‐Si:H

    Page(s): 2272 - 2281
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    We study the process of interstitial doping of hydrogenated amorphous silicon (a‐Si:H) by Li in‐diffusion and thermal annealing after Li+ implantation using secondary ion mass spectrometry, dc dark conductivity [σ(T)], electron‐spin resonance, and photothermal deflection spectroscopy measurements. All Li‐doped a‐Si:H samples were characterized by an inhomogeneous distribution of Li atoms. Doping by Li in‐diffusion at 230 °C resulted in a Li‐rich (up to 1021 cm-3) region at both sample interfaces, a large increase in σ(300 K), and the creation of deep paramagnetic (g=2.0061±0.0002, ΔHp.p.=5.4±0.4 G) defects with defect densities (up to 2×1018 cm-3) proportional to the interfacial Li concentration. Li+ implantation of a‐Si:H at 373 K resulted in the creation of deep paramagnetic (g=2.0056±0.001, ΔHp.p.=6.0±0.5 G) defects with defect densities (up to 2×1018 cm-3) proportional to the implanted Li+ dose. Isochronal vacuum annealing of Li+‐implanted a‐Si:H up to 545 K resulted in an exponential increase of σ(300 K) and an activated (Ea=+0.32 eV) decrease of the spin density with increasing anneal temperatures. Both Li in‐diffused and annealed Li+‐implanted a‐Si:H films displayed thermal equilibration behavior similar to that characteristic of P‐doped a‐Si:H, which suggests that the defect compensation model of substitutional doping of a‐Si:H is also applicable to the case of interstitial doping. However, the defect structure of a‐Si:H doped by Li in‐diffusion is significantly different than that of both undoped and P‐doped - a‐Si:H due to the precipitation of Li at the interfaces of heavily Li‐doped a‐Si:H. We discuss the origin of this behavior. View full abstract»

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  • Synchrotron radiation Bragg angle contour mapping of crack nucleation at grain boundaries

    Page(s): 2282 - 2288
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    In technical materials a critical step leading to complete macroscopic failure is not the nucleation of cracks in isolated grains, but instead the transmission of rupture from grain to grain until the entire cross section is traversed. It is difficult, in general, to employ the usual microscopic observations which could provide the keys to a comprehensive mechanistic understanding of this problem. It is shown herein that monochromatic synchrotron radiation can be used to provide Bragg angular contour maps in a rapid and precise manner. These maps enable one to quantify the local strain field tensor associated with crack nucleation and propagation through a grain boundary. Based on this analysis it is then a straightforward process to determine the other mathematical properties usually associated with second rank tensors which lead to assessment of critical parameters for crack transmission at the boundary. The application of this analytical technique is experimentally demonstrated by studies of crack formation at grain boundaries in zinc bicrystals. View full abstract»

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  • Effects of shock waves on metal‐semiconductor interfaces

    Page(s): 2289 - 2292
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    Extensive interdiffusion was found in metal‐semiconductor contacts under shock wave compression. In Al coated Si samples, selected area diffusion began at a pressure of 0.46 GPa and increased with pressure. An interdiffusion coefficient of up to 10 cm2/s was obtained. The diffusion depth was found to vary as the square root of pressure varied. However, no diffusion could be found in pressure treated Sb on Si samples. The results showed that interstitial diffusion in thermal diffusion systems was responsible for the Al‐Si interdiffusion. It demonstrated that the dominant diffusion mechanism in thermal diffusion (e.g., interstitial for Al) remains dominant under shock wave pressure diffusion. It also suggested that under shock wave pressure, the interdiffusion of metal‐semiconductor contacts may exhibit the same behavior as in the case of thermal diffusion. View full abstract»

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  • X‐ray microanalysis of InGaAs/InP multilayer structures grown by metalorganic chemical vapor deposition

    Page(s): 2293 - 2299
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    X‐ray microanalysis in a scanning transmission electron microscope can be employed to determine concentration profiles with a spatial resolution of ≲2 nm across layer interfaces in III‐V compound semiconductor multilayer structures. Here we describe its application to the InGaAs/InP multilayer system grown by metalorganic chemical vapor deposition at atmospheric pressure. The results show that even when the material is structurally perfect, there can be a significant As and Ga content beyond the boundaries of the InGaAs layers. Furthermore, the composition profiles can show a marked asymmetry relating to the growth direction. The results are consistent with previous imaging observations but provide quantitative information with high spatial resolution on individual element distributions. This combination of analytical attributes is not available using any other assessment technique. View full abstract»

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  • On the thermodynamical driving force during ion mixing of the Co‐Si system

    Page(s): 2300 - 2306
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    The relative importance between the thermodynamical driving force and kinetics in thermal annealing and ion mixing in the thermally activated regime has not been clarified. To probe the role of the thermodynamical driving force in reactions between metals and silicon, the Co‐Si system was chosen for investigation. In general, three silicide phases are formed during thermal annealing of samples consisting of Co thin films deposited on Si substrates, i.e., Co2Si (the first phase to form with a heat of formation, ΔHf=-9 kcal/g atoms), CoSi (ΔHf=-12 kcal/g atoms), and CoSi2 (the last phase to form, with ΔHf=-8.2 kcal/g atoms). Previous experiments have shown that annealing a sample of Si/CoSi/Co converts CoSi into Co2Si instead of a continuous growth of CoSi. This type of reaction is apparently unrelated to the magnitude of the thermodynamical driving force since ΔHf of CoSi is significantly larger than those of Co2Si and CoSi2, but is kinetically restricted instead. Under ion mixing conditions the kinetic restriction is expected to relax due to enhanced atomic mobilities under ion irradiation; the ion‐induced reactions should then be driven by thermodynamics; i.e., growth of the phase with the largest ΔHf is favored. In this work, phase formation induced thermally and with ion mixing in the Co‐Si system was investigated using Rutherford backscattering spectrometry and x‐ray diffraction (Read camera). It was found that in thermal annealing, Co2Si is the first phase to form and Co is the dominant moving species in the formation of Co2Si, in agreement with previous results. In ion mixing, both CoSi and Co2Si are observed to form. At low temperatures, the formation of CoSi dominates. As the substrate temperature is increased, the formation of - Co2Si becomes more significant. Co and Si are found to be the dominant moving species in the ion‐beam‐assisted formation of Co2Si and CoSi, respectively. By introducing the concept of an effective heat of formation, initial phase formation in both ion mixing and thermal annealing can be rationalized in terms of the thermodynamical driving force. View full abstract»

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  • Effects of low‐level boron doping on the photocurrent of amorphous silicon Schottky photodiodes

    Page(s): 2307 - 2312
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    We have measured the photocurrent‐electric field (Jph‐F) characteristics of slightly boron (B) doped (0≤[B2H6]/[SiH4]≤10 ppm) amorphous silicon (a‐Si:H) Schottky photodiodes with a configuration of Cr/a‐Si:H/ITO. The measurements were performed with different bias directions and two light wavelengths (555 and 660 nm), and mobility‐lifetime (μτ) products were deduced by two methods. One is by fitting the experimental plots to the theoretical curves developed by Crandall [Semiconductors and Semimetals (Academic, Orlando, FL, 1984), Vol. 21, Pt. B, p. 245.]. The other is a new one we have proposed where the transition electric field Ftr, at which Jph changes from space‐charge‐limited current to the theoretical curve given by Crandall, is applied to the relationship μτFtr=L, where L is the thickness of a‐Si:H. It was found that the former method is applicable only where a‐Si:H is homogeneously illuminated and no space charge is formed. On the other hand, the latter method is effective where a‐Si:H is inhomogeneously illuminated and a space charge is formed in the carrier transit region. The μhτh deduced by the latter method increased from 2×10-9 to 3×10-8 cm2/V when the B‐doping ratio was increased from 0 to 3 ppm, but remained nearly constant with further doping. In contrast, μeτe monotonically decreased from 2×10-8 to 2×10-9 cm2/V with increased doping. The (μτ)fit deduced by the former method coincides with the μhτh at doping ratios higher than 3 ppm, but did not at lower doping ratios probably becau- se of a space‐charge formation by deep hole trapping and incomplete homogeneous illumination. These changes in μτ are discussed microscopically in terms of the charge state of the dangling bond state. View full abstract»

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  • Study of the low‐pressure chemical‐vapor‐deposited tungsten‐silicon interface: Interfacial fluorine

    Page(s): 2313 - 2320
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    Single‐crystal silicon 〈100〉 substrates uniformly doped at ≳12 Ω cm with boron were deposited with ∼800 Å of low‐pressure chemically vapor deposited W in a hot‐quartz‐walled (Anicon) system at a deposition temperature of 300 °C. The samples studied include an as‐deposited sample and two others which were post‐deposition annealed at 600 °C in Ar for 15 min each. X‐ray photoelectron spectroscopy (XPS) coupled with an Ar+ ion sputter profiling technique was employed to investigate these structures as a function of depth. Particular emphasis was placed on the depth distribution, content, and chemical state of the fluorine present. Rutherford backscattering spectrometry and x‐ray diffraction were used to corroborate the XPS data. Results show that, for the as‐deposited and 600 °C annealed sample, the maximum concentration of fluorine (0.6–0.8 at. %) is observed, not at the W/Si interface, but rather at the W (H2 reduction)/W (Si displacement) interface. For the sample annealed at 850 °C, WSi2 is formed in the overlayer, and the peak in the F profile corresponds to the position of the WSi2/Si interface. The maximum concentration of fluorine is reduced by approximately 75% to 0.23 at. % in this sample. From the XPS spectra of the F 1s region, the chemical species of fluorine present in these samples have been identified as WF6, WF5, and WF4. View full abstract»

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  • Anomalous capacitance in selenium Schottky diodes

    Page(s): 2321 - 2327
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    In measurements of capacitance as a function of bias on selenium‐metal diodes, an anomalous minimum has been observed at frequencies below about 1 kHz. As the frequency is increased, the minimum disappears. For Se‐Bi, Se‐Au, Se‐Tl, and Se‐Mg diodes, prepared by evaporation of the metal on a layer of crystallized selenium, the voltage at which the minimum occurs shifts systematically with the magnitude of the barrier height, as determined from capacitance at reverse‐bias and current‐voltage characteristics. However, no singularities have been observed in parallel incremental resistance at these particular voltages. A simple equivalent circuit model is proposed, which phenomenologically accounts essentially for the observed facts. View full abstract»

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  • Effects of high pressure on silicon metal‐oxide‐semiconductor structures

    Page(s): 2328 - 2331
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    The frequency and bias dependence of capacitance in a planar silicon metal‐oxide‐semiconductor structure has been successfully measured in a diamond anvil high‐pressure cell. Electrical contact was achieved with gold ribbon leads passed between one diamond and an insulator‐coated pressure seal. Pressure effects on the SiO2 thickness and the silicon surface state profile were separated from changes in lead capacitance and leakage. As the pressure was increased to 30 kbar, SiO2 was compressed 12% normal to the planar surface, but only partially relaxed on a time scale of days after pressure release. The surface state profile, with a minimum at 1×1012 cm-2  eV-1, was essentially unaffected by pressure. Above 30 kbars leakage currents severely limited capacitance interpretation. View full abstract»

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  • Thermoelectric power and electrical resistivity of crystalline antimony telluride (Sb2Te3) thin films: Temperature and size effects

    Page(s): 2332 - 2341
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    Crystalline Sb2Te3 thin films of different thicknesses have been prepared by subsequent annealing (at 500 K) of vacuum deposited, as‐grown, amorphous thin films of Sb2Te3 prepared on glass substrates at room temperature. Thermoelectric power and electrical resistivity of these annealed (crystalline) films have been determined as a function of temperature. The size dependence of thermoelectric power and electrical resistivity have been analyzed by the effective mean free path model of size effect. It is found that both the thermoelectric power and the electrical resistivity are linear functions of the reciprocal of thickness of the films. The data from the analyses of thermoelectric power and electrical resistivity have been combined to evaluate important material parameters such as carrier concentration, their mean free path, Fermi energy, and effective mass. The values of some of these are compared with the previous available values from literature. View full abstract»

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  • Trap creation in silicon dioxide produced by hot electrons

    Page(s): 2342 - 2356
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    Trap creation in both the bulk of silicon dioxide films and at its interfaces with silicon and metallic contacting electrodes is shown to depend on the presence of hot electrons in the oxide. For thick oxides (≥100 Å), little trap creation is observed in the near‐thermal transport regime at electric field magnitudes less than 1.5 MV/cm. At these low fields, electrons travel in a streaming fashion close to the bottom of the oxide conduction band at energies less than that of the dominant optical phonon mode at 0.153 eV. At higher electric fields, the rate of bulk trap creation is proportional to the average energy of the hot electrons, which move in a dispersive manner and can reach energies as large as 4 eV. For thin oxides (≪100 Å) where electrons can travel ballistically (i.e., without scattering), traps are not produced unless injected electrons acquire more than 2 eV of kinetic energy from the applied electric field, regardless of the magnitude of this field. All data on both thin and thick oxides are shown to give a threshold for trap creation of about 2.3 eV by the hot electrons in the oxide conduction band. Also, trap creation is shown to be suppressed by lowering the lattice temperature below ≊150 K. Our results are discussed in terms of a model involving hydrogen‐related‐species release from defect sites near the anode by the hot electrons and the subsequent motion of these molecules to regions near the cathode where they can interact with the lattice and form the trapping sites which are measured. View full abstract»

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Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

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P. James Viccaro
Argonne National Laboratory