Showing papers in "Journal of Applied Physics in 1975"
TL;DR: In this article, Boron doses of 1×1012-5×1015/cm2 were implanted at 60 keV into 1-μm-thick polysilicon films and Hall and resistivity measurements were made over a temperature range −50-250 °C.
Abstract: Boron doses of 1×1012–5×1015/cm2 were implanted at 60 keV into 1‐μm‐thick polysilicon films. After annealing at 1100 °C for 30 min, Hall and resistivity measurements were made over a temperature range −50–250 °C. It was found that as a function of doping concentration, the Hall mobility showed a minimum at about 2×1018/cm3 doping. The electrical activation energy was found to be about half the energy gap value of single‐crystalline silicon for lightly doped samples and decreased to less than 0.025 eV at a doping of 1×1019/cm3. The carrier concentration was very small at doping levels below 5×1017/cm3 and increased rapidly as the doping concentration was increased. At 1×1019/cm3 doping, the carrier concentration was about 90% of the doping concentration. A grain‐boundary model including the trapping states was proposed. Carrier concentration and mobility as a function of doping concentration and the mobility and resistivity as a function of temperature were calculated from the model. The theoretical and ex...
2,657 citations
TL;DR: In this article, the pressure dependence of the R1 ruby fluorescence line has been calibrated at 25°C against the compression of NaCl using the Decker equation of state for NaCl.
Abstract: The pressure dependence of the R1 ruby fluorescence line has been calibrated at 25 °C against the compression of NaCl. Pressures are determined using the Decker equation of state for NaCl. The dependence is linear to 195 kbar following the equation PNaCl=2.746(Δλ), where P is in kbar and Δλ in A. The uncertainty in the value of the slope, dp/dλ, expressed in terms of a 95% confidence interval is 2.746±0.014 kbar A−1. The coefficient of the quadratic term (Δλ)2 is not significantly different from zero; and the quadratic term makes indeed a negligible contribution to the fit. Taking into account the reported uncertainty associated with the Decker equation of state for NaCl, the value of the slope is 2.740±0.016 kbar A−1 within a 95% confidence interval.
1,681 citations
TL;DR: Gain spectra for GaAs double-heterostructure junction lasers have been obtained with high resolution by using an automated data aquisition system to analyze the Fabry−Perot resonance modulation in the spontaneous emission spectra as mentioned in this paper.
Abstract: Gain spectra for GaAs double−heterostructure junction lasers have been obtained with high resolution. This is accomplished by using an automated data aquisition system to analyze the Fabry−Perot resonance modulation in the spontaneous emission spectra. For active regions doped with Ge at a level of 4×1017 cm−3, the gain in the TE polarization at a fixed wavelength increases linearly with current, below lasing threshold. However, the peak gain (at a variable wavelength) increases slightly faster than linearly with current. The photon energy at which gain is a maximum increases logarithmically with current. Gain in the TM polarization depicts the same general behavior as that for the TE case, except that it is slightly less than the TE gain. It is concluded that for this particular doping the spectral gain characteristics are intermediate between those for undoped and heavily doped active regions. Above the threshold for lasing in the TE mode the TE gain spectra are well saturated, with new fine details revealed in the saturated spectra. On the other hand, gain in the nonlasing TM polarization is not well saturated above threshold, with marked differences in gain between high and low photon energies relative to the TE lasing energy.
836 citations
TL;DR: The thermal expansion of AlN, cubic BN, and BP has been measured from 77 to 1300 K by x−ray techniques as mentioned in this paper, and the derived thermal expansion coefficients are compared with those of diamond, Si, Ge, SiC, GaP, and BeO using the Debye temperature as a scaling parameter.
Abstract: The thermal expansion of AlN, cubic BN, and BP has been measured from 77 to 1300 K by x−ray techniques The derived thermal expansion coefficients are compared with those of diamond, Si, Ge, SiC, GaP, and BeO using the Debye temperature as a scaling parameter It is apparent that the thermal expansion of Si is the smallest, SiC is intermediate, and all of the others are larger The thermal expansion of Mo and W is also reviewed in order to determine how well these metals match the thermal expansion of the adamantine or diamondlike crystals
648 citations
TL;DR: In this paper, a closed-form analysis of saturable absorber mode locking of a homogeneously broadened laser is presented for the case of a short relaxation time of the saturable absorbber.
Abstract: This paper presents a closed‐form analysis of saturable absorber mode locking of a homogeneously broadened laser. A solution is obtained for the case of a short relaxation time of the saturable absorber. This pulse is a hyperbolic secant as a function of time. For each choice of parameters two pulse widths are found. A stability analysis shows that the solution of greater width is stable. The requirements for achieving mode locking with a fast saturable absorber are stated. The effect of a time‐varying laser medium gain is investigated analytically.
617 citations
TL;DR: The absorption coefficient α for GaAs at room temperature was determined in the spectral range from 1.3 to 1.6 eV by transmission measurements for 10−α⩽103 cm−1 and by a Kramers−Kronig analysis of the reflectance for α≳103cm−1 as mentioned in this paper.
Abstract: The absorption coefficient α for GaAs at room temperature was determined in the spectral range from 1.3 to 1.6 eV by transmission measurements for 10⩽α⩽103 cm−1 and by a Kramers−Kronig analysis of the reflectance for α≳103 cm−1. Measurements were made on high−purity n−type samples, n−type samples with free−electron concentrations from 5×1016 to 6.7×1018 cm−3, p−type samples with free−hole concentrations from 1.5×1016 to 1.6×1019 cm−3, and p−type samples heavily doped with the amphoteric impurity Si. These data show that near the direct energy gap Eg the shape of the α−vs−photon−energy curve is strongly dependent on the impurity concentration.
570 citations
TL;DR: In this paper, an n-channel MOS transistor with palladium gate was fabricated and the threshold voltage of this transistor was found to depend on the partial pressure of hydrogen in the ambient atmosphere.
Abstract: An n‐channel MOS transistor with palladium gate was fabricated. The threshold voltage of this transistor was found to depend on the partial pressure of hydrogen in the ambient atmosphere. At a device temperature of 150 °C, 10 ppm hydrogen in air is easily detected, and in nitrogen or argon the sensitivity is considerably larger. A model, based on hydrogen adsorption on the palladium–silicon dioxide interface, is proposed. This model explains the device behavior and is also able to predict the absolute sensitivity for hydrogen in argon.
467 citations
TL;DR: In this paper, the authors present an understanding of the conduction mechanisms and physical processes relevant to the performance of ZnO-based ceramic varistors and show that the qualitative features of highly nonlinear conductivity are largely independent of the details of varistor composition or processing but rather appear to be a general effect engendered by a microstructure of conducting grains surrounded by thin insulating oxide barriers.
Abstract: This paper outlines our present understanding of the conduction mechanisms and physical processes relevant to the performance of ZnO−based ceramic varistors. Varistor behavior is determined by the gross ceramic microstructure of the device as well as by the localized conduction processes which occur between grains. We show that the qualitative features of the highly nonlinear conductivity are largely independent of the details of varistor composition or processing but rather appear to be a general effect engendered by a microstructure of conducting grains surrounded by thin insulating oxide barriers. Evidence is presented from a variety of sources that this intergranular layer is ∼100 A in thickness resulting in grain−to−grain fields of F∼106 V/cm. The conduction mechanism at breakdown is consistent with a Fowler−Nordheim tunneling process obeying a current−density−vs−field relation given by J∝exp(−γ/F), where γ is a constant. At somewhat lower fields (prebreakdown region) the conduction process follows a...
412 citations
TL;DR: In this paper, an exact (i.e., to arbitrary accuracy) solution for the complex admittance of Schottky-barrier diodes as a function of temperature provided a spectroscopy of deep trapping levels.
Abstract: Measurements of the complex admittance of Schottky‐barrier diodes as a function of temperature provide a spectroscopy of deep trapping levels. The measurement conditions are usually close to thermal equilibrium, thus assuring the validity of equilibrium occupation probabilities. An exact (i.e., to arbitrary accuracy) solution for the junction admittance is given. The problem is reduced to solution of a simple initial‐value problem, the final integration being carried out by computer. It is shown that the dispersion in capacitance due to slow trapping levels can lead to serious errors in estimates of junction doping concentrations and barrier height determinations. Examples are given for p‐type ZnTe where Shockley‐Read‐Hall (SRH) centers are dominant and for n‐type CdTe and Cd1−xZnTe where double‐acceptor centers are dominant. For junctions formed on CdTe : Ga it is shown that one of the steps in capacitance observed in a thermally stimulated capacitance survey is actually a high‐frequency response step an...
395 citations
TL;DR: In this article, the authors used the electron beam plasma technique to synthesize solid solutions of Ga1−xInxN and found that the solid solution of GaN can be synthesized over the entire composition region.
Abstract: By the use of the electron beam plasma technique, it has been found that the solid solutions of Ga1−xInxN can be synthesized over the entire composition region. From the optical measurements, the direct energy gap at 78 °K was determined to be 3.46 eV for GaN and 2.11 eV for InN. Also its composition dependence was found to deviate downward from linearity. From the infrared reflectivity measurement and the resultant K‐K dispersion analysis, the transverse optical frequencies for long‐wavelength phonons of GaN and InN were 563 and 478 cm−1, respectively. The optical phonons in this quasibinary system were concluded to exhibit a one‐mode–type behavior. The Brout sum rule was discussed for a large number of the diatomic crystals of ANB8−N type and its relation with respect to the reduced mass was derived as Σiω2i(k=0) =A μ−1.5. According to this relation, the longitudinal optical frequency of InN was deduced to be 694 cm−1. On the other hand, from the result of the annealing treatment for the solid‐solution ...
346 citations
TL;DR: In this article, the boundary radiation heat loss method is investigated for the flash method in measuring thermal diffusivity, and correction procedures for heat loss are tested experimentally using AXM−5Q (POCO) graphite.
Abstract: The boundary radiation heat loss method is investigated for the flash method in measuring thermal diffusivity. Present correction procedures for heat loss are tested experimentally using AXM−5Q (POCO) graphite. In addition, a new method for radiation loss correction is presented based solely on the heating portion of the temperature rise curve. Using the new method, corrections of 35% can be made within a ±3% error. The thermal diffusivity results calculated using the adiabatic expression for various portions of the fractional rise curve and for various heat losses are also presented.
TL;DR: The effective thermal conductivity of suspensions of 50− and 100−μ-diam polystyrene spheres in aqueous sodium chloride or glycerine, flowing in laminar motion, has been shown to be a function of the state of the motion as discussed by the authors.
Abstract: The effective thermal conductivity of suspensions of 50− and 100‐μ‐diam polystyrene spheres in aqueous sodium chloride or glycerine, flowing in laminar motion, has been shown to be a function of the state of the motion (unlike single‐phase fluids) and has been seen to be as much as 3 times the thermal conductivity of stationary suspensions Detailed experiments have indicated its dependence upon the particle concentration, particle size, shear rate, kinematic viscosity, and thermal diffusivity of the suspending liquid, and tube diameter and length The Graetz solution corresponding to uniform wall temperature was used to determine the value of thermal conductivity in an apparatus calibrated with tap water The over‐all accuracy of the results is within 10%
TL;DR: In this article, a GaAs−GaAlAs heterostructure laser is modeled as a stripe heat source embedded in a layered structure, and an analytic expression is given for the steady-state thermal resistance 〈R〉 of the model.
Abstract: A GaAs−GaAlAs heterostructure laser is modeled as a stripe heat source embedded in a layered structure, and an analytic expression is given for the steady−state thermal resistance 〈R〉 of the model. Over the range of typical layer thicknesses and conductivities, and for heat generated uniformly in the active region, 〈R〉 varies between 14 and 31 K/W for a 12×375−μ active region. Four types of heat sinks are shown to contribute an additional 3 to 10 K/W. Design implications are drawn for various properties including layer thicknesses, heat−sink and bond parameters, and radiative heat transfer by spontaneous emission. In disagreement with the common tacit assumption of a unique active−region temperature, it is found that about 40% of the temperature drop within the laser occurs in the active region (center to edge).
TL;DR: In this paper, analytical and numerical solutions to the heat-conduction equation are obtained for the heating of absorbing media with pulsed lasers, and the spatial and temporal form of the temperature is determined using several different models of the laser irradiance.
Abstract: Analytical and numerical solutions to the heat-conduction equation are obtained for the heating of absorbing media with pulsed lasers. The spatial and temporal form of the temperature is determined using several different models of the laser irradiance. Both surface and volume generation of heat are discussed. It is found that if the depth of thermal diffusion for the laser-pulse duration is large compared to the optical-attenuation depth, the surface- and volume-generation models give nearly identical results. However, if the thermal-diffusion depth for the laser-pulse duration is comparable to or less than the optical-attenuation depth, the surface-generation model can give significantly different results compared to the volume-generation model. Specific numerical results are given for a tungsten target irradiated by pulses of different temporal durations and the implications of the results are discussed with respect to the heating of metals by picosecond laser pulses.
TL;DR: In this paper, the properties of a harmonically bound radiatively thermalized ion gas were investigated by studying the behavior of an electron cloud stored in a Penning trap, and a simple model characterizing ions contained in an electromagnetic trap was proposed and tested by investigating the electromagnetic−dynamic behavior of these electrons subject to various external perturbations.
Abstract: The properties of a harmonically bound radiatively thermalized ion gas were investigated by studying the behavior of an electron cloud stored in a Penning trap. A simple model characterizing ions contained in an electromagnetic trap is proposed and tested by investigating the electromagnetic−dynamic behavior of these electrons subject to various external perturbations. The ion calorimeter realized in such a system is also discussed; particular attention is devoted to sensitivity to heat inputs into the various degrees of freedom.
TL;DR: In this paper, the electrical properties of GaAs single crystals were measured after annealing at various elevated temperatures in controlled atmospheres, and the entropy and enthalpy changes for the vacancy formation reactions at the surface were evaluated, based on experimental data and thermodynamic analysis.
Abstract: The electrical properties of GaAs single crystals were measured after annealing at various elevated temperatures in controlled atmospheres. Two types of defects were introduced as the result of annealing: (i) donors having a high concentration near the surface and (ii) acceptors having a lower surface concentration but extending further into the crystal. The As overpressure dependencies indicate that the donors are As vacancies and the acceptors are Ga vacancies since their respective concentrations are proportional to iPAs4−1/4 and iPAs4+1/4. The entropy and enthalpy changes for the vacancy formation reactions at the surface were evaluated, based on experimental data and thermodynamic analysis. The diffusion coefficients of vacancies follow the relations D (VGa) =2.1×10−3 exp(−2.1/kT) and D (VAs) =7.9×103 exp(−4.0/kT). Both types of vacancies form nonradiative centers as determined from photoluminescence experiments.
TL;DR: In this article, the relative contributions of two types of pinning centers, grain boundaries and second phase particles, to flux pinning have been determined by correlating Jc with microstructure.
Abstract: Very high critical current densities (Jc=8×105 A/cm2 at 4.2 K and 6 T) have been achieved in commercial Nb3Sn tape and more recently in multifilamentary Nb3Sn superconductors. The relative contributions of two types of pinning centers, grain boundaries and second phase particles, to flux pinning have been determined by correlating Jc with microstructure. It was found that grain boundaries were the only defect present in sufficient density to account for flux pinning in the multifilamentary Nb3Sn material. The dependence of Jc on grain size was measured, and the relationship between pinning force and grain size is discussed in terms of current theories for flux pinning in type‐II superconductors.
TL;DR: In this paper, the behavior of a point to plane discharge has been analyzed electrically and optically for centimetric gaps in air at atmospheric pressure, and it has been shown that for both steady and pulsed applied potentials the evolution always consists of the sequence: primary streamer, secondary streamers, dark space (more or less pronounced), transient arc.
Abstract: The behavior of a point to plane discharge has been analyzed electrically and optically for centimetric gaps in air at atmospheric pressure. This shows that for both steady and pulsed applied potentials the evolution always consists of the sequence: primary streamer, secondary streamer, dark space (more or less pronounced), transient arc. Experiments are presented that are directed towards obtaining an indication of the physical meaning of these different phases. A time‐resolved spectroscopic analysis leads to an evaluation of the electron energy within the secondary streamer of ∼1.4 eV. This indicates that the secondary streamer does not correspond to a very strong ionizing region. Three significant observations have been obtained using a device that is able to distinguish between conduction and displacement currents: (i) the secondary streamer occurs within a conducting filament built up by the primary streamer, (ii) when the primary streamer arrives at the plane, a cathode region appears giving continu...
TL;DR: In this article, surface crystallization of a glass sample implanted with 285-keV Au+ ions at 550°C results in the growth of colloidal Au particles of 18-35°A radius.
Abstract: Surface crystallization of a Au+‐ion‐implanted lithia‐alumina‐silica glass has been realized. Annealing of a glass sample implanted with 285‐keV Au+ ions at 550 °C results in the growth of colloidal Au particles of 18–35‐A radius. The Au particles constitute sites for the precipitation of lithium metasilicate crystals at 550 °C. Further annealing at 750 °C allows the growth of quartz and β‐spodumene crystals. The crystallized surface obtained after the high‐temperature anneal was characterized by a Knoop microhardness number of 626, which is of the order of that obtained for commerical volume‐crystallized glass‐ceramics of similar composition.
TL;DR: In this article, an analysis of the one-dimensional constant-loss theory of secondary electron emission, maximum yield, primary electron energy at maximum yield (Eom), and both crossover energies EIoc and EIIoc are shown to depend on the surface and bulk properties of the emitting material through simple relations.
Abstract: From an analysis of the one‐dimensional constant‐loss theory of secondary electron emission, maximum yield (δm), primary electron energy at maximum yield (Eom), and both crossover energies EIoc and EIIoc are shown to depend on the surface and bulk properties of the emitting material through simple relations. In particular, the results strongly suggest that the first crossover energy can be very dependent on surface properties, whereas the energy at maximum yield is entirely controlled by bulk properties. Refinement of the low‐energy part of the reduced yield curve by means of the results of the more realistic three‐dimensional theory leads to the development of the expression EIoc=0.51Eomδm−1.32. Comparison between theory and experiment for several secondary‐emitting materials is presented to demonstrate the accuracy of this useful relation. Finally, the implications of these results for different classes of materials are discussed in terms of basic physical properties, such as density, electrical conduct...
TL;DR: In this paper, an explanation for the "bounce" in optical transmission of a twisted nematic cell between polarizers after switching off the applied field has been given, and it is shown that fluid motion is essential to the occurrence of these phenomena.
Abstract: The Ericksen‐Leslie equations, describing the dynamic behavior of nematic liquid crystals, have been applied to a twisted nematic layer and have been numerically solved for a number of cases. The results account well for the observed dynamic behavior of displays using a twisted nematic layer. In particular, an explanation is given for the ’’bounce’’ in the optical transmission of a twisted nematic cell between polarizers after switching off the applied field. Materials having a frequency dependence of the sign of the dielectric anisotropy show a reversal of twist after the frequency of the applied field has been switched. This can also be explained. It is shown that fluid motion is essential to the occurrence of these phenomena.
TL;DR: In this article, experimental evidence for gain-induced guiding and refractive-index antiguiding along the junction plane of stripe-geometry double-heterostructure GaAs was presented.
Abstract: We report on experimental evidence for gain−induced guiding and refractive−index antiguiding along the junction plane of stripe−geometry double−heterostructure GaAs lasers. It had previously been found that carrier diffusion out of the active region leads to a gain profile along the junction plane that can be approximated by a parabolic variation. This results in a lowest−order mode having a Gaussian profile, a cylindrical phase front, and a constant radius of curvature. This curvature accounts for the astigmatism always observed in the output beam from stripe−geometry GaAs lasers, where gain guiding dominates index guiding. Experimental determinations of the far−field diffraction angle, ϑ, and the beam width, 2w, at the laser mirror in the junction plane enable us to calculate the parameters characterizing the gain distribution responsible for mode confinement, as well as a negative refractive−index increment which would tend to defocus the mode. The negative index increment, as measured between the center and the edges of the stripe, appears to be related to a competition between a negative free−carrier effect and a positive thermal focusing mechanism. Above threshold, changes in ϑ and w with current imply changes in the gain−guiding mechanism. The theory implies in particular a decrease in gain at the center of the stripe and an increase at the edges with an increase in current.
TL;DR: In this article, optical microscopy, differential scanning calorimetry, and infrared spectroscopy are used to study the high-temperature isothermal crystallization of high-molecular-weight poly(vinylidene fluoride) poly(VVF2).
Abstract: In this study, optical microscopy, differential scanning calorimetry, and infrared spectroscopy are used to study the high‐temperature isothermal crystallization of high‐molecular‐weight poly(vinylidene fluoride) It is shown that there exists a temperature domain in which both the α and β phases of PVF2 can be grown concurrently and in competition with each other to form two distinct populations of spherulites which are characterized by different diameters, band periods, and melting points In addition, a time‐ and temperature‐dependent crystal‐crystal transition from the α phase to the γ form can be induced in this high‐temperature crystallization region to produce spherulites which melt 15–20 ° above the melting point of the original α phase This transformation exhibits nucleation and propagation characteristics which in some regions can compete with the normal growth of the α phase to produce unique ’’wagon‐wheel’’ spherulitic structures
TL;DR: In this paper, a numerical method was used to solve the hydrodynamic equations with negligible rates of change of momentum and angular momentum, but without other approximations, in a liquid-crystal twist cell.
Abstract: We describe and present results of a numerical method we have used to solve the hydrodynamic equations with negligible rates of change of momentum and angular momentum, but without other approximations, in a liquid‐crystal twist cell. We verify that the ’’bounce’’ in transmission of normally incident light that is observed when the electric potential across the cell is turned off is an effect of shear flow (backflow) which causes temporary reverse rotation of directors in the middle of the cell. It is not an inertial effect. Inertial effects would have transient times much shorter than the times associated with the optical bounce. When fluid flow is omitted, as in our previous papers, molecules do not tilt backward and the ’’optical bounce’’ occurs only for light that is obliquely incident in one quadrant. A qualitative explanation of the optics of the bounce is given, in addition to numerical results.
TL;DR: In this article, a ferroelectric field effect transistor (FET) was constructed using a thin film of bismuth titanate (Bi4Ti3O12) deposited on a Si substrate by rf sputtering.
Abstract: A ferroelectric field‐effect transistor has been investigated using a thin film of bismuth titanate (Bi4Ti3O12) deposited on a Si substrate by rf sputtering. Achievement of the ferroelectric polycrystalline Bi4Ti3O12 films without any cracks necessitates postdeposition heat treatment in air at temperatures ?550 °C for 30 min. The film, heat treated at 650 °C, has a remanent polarization of 4.0 μC/cm2 and a coercive field of about 250 kV/cm at 1 kHz. A FET having a gate structure of Bi4Ti3O12‐SiO2‐Si was fabricated, where the SiO2 served to prevent charge injection from Si into the ferroelectric film. (This process would degrade the retention of memorized states.) The FET can be switched by voltages of as low as 15 V applied to the gate. The on and off states are very stable at room temperature.
TL;DR: In this paper, Relativistic Brillouin solutions have been derived for electron flow in crossed electric and magnetic fields and an approximate analytical expression for the anode current is derived.
Abstract: Relativistic Brillouin solutions have been derived for electron flow in crossed electric and magnetic fields. The application of these solutions to the high ν/γ diode is discussed and an approximate analytical expression for the anode current is derived. Measurements of diode current are compared to the theoretical and empirical expressions for diode current which have been developed.
TL;DR: A review of the present knowledge of the mechanical behavior of metallic glasses is given in this article, with a brief discussion of their structures and how these relate to the small change (about 1%) in mass density that occurs when a metallic glass is crystallized.
Abstract: This is a review of the present knowledge of the mechanical behavior of metallic glasses. It begins with a brief discussion of their structures and how these relate to the small change (about 1%) in mass density that occurs when a metallic glass is crystallized. Then the elastic, anelastic, plastic, and strength properties are reviewed. Mechanisms of plastic flow are discussed. A quantitative dislocation model that successfully predicts the observed yield stresses is presented. Needs for producing future understanding are outlined.
TL;DR: In this article, a computer algorithm is presented which allows simultaneous consideration of selfphase modulation and dispersion for predicting temporal shape changes during the propagation of plane-wave intense light pulses.
Abstract: A computer algorithm is presented which allows simultaneous consideration of self‐phase modulation and dispersion for predicting temporal shape changes during the propagation of plane‐wave intense light pulses. The algorithm entails considering propagation alternately in regions where only one of the two above effects is operative. It is shown for clear materials that the parameters characterizing propagation are the nonlinear index change, the wavelength λ, the relaxation time of the nonlinearity, and the disperison parameter λ3(d2n/dλ2). The thickness of material over which a pulse will significantly reshape is found to be √λ times the geometric length of the pulse divided by the square root of the product of the dispersion parameter and the maximum nonlinear index. It is demonstrated that dispersion significantly modifies the self‐steepening concept of DeMartini, Townes, Gustafson, and Kelley. Numerical simulations of propagation in CS2 indicate that, after sufficient travel, a shock can form on the le...
TL;DR: In this paper, the sputtering yield of vacuum-deposited gold targets has been measured with 18 different 45-keV ions throughout the periodic system and the results are compared with previously reported results obtained with copper, silicon, and silver targets and with the predictions of the Sigmund theory.
Abstract: The sputtering yield of vacuum‐deposited gold targets has been measured with 18 different 45‐keV ions throughout the periodic system. The results are compared with previously reported results obtained with copper, silicon, and silver targets and with the predictions of the Sigmund theory. The variation in the yield with projectile atomic number is found to be consistent with theory although rather large deviations are found for both heavy and light projectiles. The large experimental yields for heavy projectiles as well as the maximum in the energy dependence of the yield, which is more pronounced than predicted by theory, are explained by nonlinear effects in very dense collision cascades. This interpretation is supported by data obtained from irradiation with atomic and molecular ions of the same elements. The deviations for light projectiles are considered mainly to be due to the lack of a surface correction term in the theory.
TL;DR: The microstructure of a complex multicomponent varistor ceramic based on ZnO with small additions of antimony, bismuth, cobalt, manganese, and tin oxides has been elucidated using a variety of structural techniques as mentioned in this paper.
Abstract: The microstructure of a complex multicomponent varistor ceramic based on ZnO with small additions of antimony, bismuth, cobalt, manganese, and tin oxides has been elucidated using a variety of structural techniques. Three crystalline phases are found to coexist in the sintered material. The bulk phase consists of a polycrystalline matrix of ZnO doped with Co(II). The ZnO grains are separated from one another by a Bi2Zn4/3Sb2/3O6 pyrochlore phase which forms a three−dimensional threadlike network, indicative of a liquid phase at high temperatures. A Zn(Zn4/3Sb2/3)O4 spinel constitutes the third phase and forms well−faceted octahedral crystals located frequently at grain boundaries between the ZnO and occasionally within the grains. This phase acts as a grain growth moderator for ZnO by anchoring the boundaries during sintering, but plays no role in the nonlinear characteristic of the varistor. A quasiequilibrium between the pyrochlore and spinel has been established such that formation of the spinel is favored at high temperatures. The over−all varistor microstructure may be described as a three−dimensional series−parallel network of ZnO−pyrochlore junctions.