Showing papers in "Journal of Applied Physics in 1979"
TL;DR: In this article, it was shown that a reliable value of the barrier height can be obtained even if there is a series resistance which would hamper the evaluation of the standard lnI•vs•V plot.
Abstract: It is shown that by plotting the function F (V) =V/2−(kT/q) ln(I/AA**T2) a reliable value of the barrier height can be obtained even if there is a series resistance which would hamper the evaluation of the standard lnI‐vs‐V plot. A theoretical examination of F (V) is followed by experimental plots for some common Schottky‐barrier diodes.
1,246 citations
TL;DR: In this paper, the extent to which gas surface chemical reactions can be enhanced by energetic radiation (primarily ions and electrons) incident on the surface is described and some technological implications of this process in plasma etching technology and lithography are considered.
Abstract: The extent to which gas‐surface chemical reactions can be enhanced by energetic radiation (primarily ions and electrons) incident on the surface is described. Emphasis is placed on chemical systems which lead to volatile reaction products. In particular, the reactions of Si, SiO2, and Si3N4 with XeF2, F2, and Cl2 are examined experimentally. Possible mechanisms for the radiation‐induced enhancement are discussed and some technological implications of this process in plasma etching technology and lithography are considered.
660 citations
TL;DR: In this article, electric field effects on the thermal emission of traps in a diode have been studied and compared with experimental data on deep centers in GaAs, consistent with a thermal equivalent of the optical Franz-Keldysh effect.
Abstract: Electric field effects on the thermal emission of traps in a diode have been studied. Calculations were performed and compared with experimental data on deep centers in GaAs. The results are consistent with a thermal equivalent of the optical Franz‐Keldysh effect.
503 citations
TL;DR: In this paper, the details of the interface region of a molecular beam epitaxially grown Al single crystal on a single-crystal substrate were studied using X-ray diffraction and total external reflection.
Abstract: A new technique utilizing conventional x‐ray diffraction in conjunction with total external reflection has provided a powerful tool for studying ordered interfaces and surface phenomena. It has been used in this work to study the details of the interface region of a molecular beam epitaxially grown Al single crystal on a molecular beam epitaxially grown GaAs single‐crystal substrate. A simple model including variations of the lattice parameter and disorder in the interface region is in agreement with these experimental results.
482 citations
TL;DR: In this article, a theory was presented which quantitatively accounts for the important features of conduction in ZnO-based metaloxide varistors, which predicts a varistor breakdown voltage of 3.2 V/grain boundary for n0=1017 carriers' cm−3 and T=300 K.
Abstract: A theory is presented which quantitatively accounts for the important features of conduction in ZnO‐based metal‐oxide varistors. This theory has no adjustable parameters. Using the known values of the ZnO band gap, donor concentration n0, and low‐voltage varistor leakage‐current activation energy, we predict a varistor breakdown voltage of ?3.2 V/grain boundary for n0=1017 carriers cm−3 and T=300 °K. This compares well with measurements on a single grain‐grain junction. The highly nonlinear varistor conduction derives from electron tunneling ’’triggered’’ by hole creation in the ZnO when the conduction band in the grain interior drops below the top of the valence band at the grain interface. The theory predicts coefficients of nonlinearity α=d (lnI)/d (lnV) as high as 50, or even 100.
427 citations
TL;DR: In this article, a model is developed to describe the potential barriers which often occur at grain boundaries in polycrystalline semiconductors, where the resistance of such materials is determined by thermionic emission over these barriers.
Abstract: A model is developed to describe the potential barriers which often occur at grain boundaries in polycrystalline semiconductors. The resistance of such materials is determined by thermionic emission over these barriers. The dc grain‐boundary current density as a function of applied voltage is calculated using several forms for the density of defect states within the boundary region. In all cases, the currents are Ohmic at low voltages; they can attain a quasisaturated level at intermediate voltages, and they display a sharp bias dependence at high voltages. The details of the intermediate and high‐voltage characteristics are found to depend strongly on the grain‐doping density and on the density and energy distribution of defect states at the grain boundary. Contrary to previous assertions, we find that the large current‐voltage nonlinearities found in real materials are most likely associated with defect‐state densities that decrease above the zero‐bias Fermi level. The results of the model are compared ...
423 citations
TL;DR: In this article, the optical second-harmonic coefficient dijk of the new nonlinear crystal 2.methyl-4.nitroaniline (MNA) was measured.
Abstract: We have grown and measured the optical second‐harmonic coefficient dijk of the new nonlinear crystal 2‐methyl‐4‐nitroaniline (MNA). We find that the dijk are very large with d12 being 5.8 times larger than d31 of LiNbO3 giving a birefringence phase‐matching figure of merit d2/n3 which is 45 times larger than LiNbO3. The other coefficient d11 is 40 times larger than LiNbO3, giving a huge figure of merit which is 2000 larger than LiNbO3.
398 citations
TL;DR: The ESR Pb center has been observed in thermally oxidized singlecrystal silicon wafers, and compared with oxide fixed charge Qss and oxidation-induced interface states Nst.
Abstract: The ESR Pb center has been observed in thermally oxidized single‐crystal silicon wafers, and compared with oxide fixed charge Qss and oxidation‐induced interface states Nst. The Pb center is found to be located near the interface on (111) wafers. Its g anisotropy is very similar to that of known bulk silicon defects having SiIII bonded to three other Si atoms; the Pb unpaired electron orbital, however, is exclusively oriented normal to the (111) surface. The Pb center cannot be identified with any other known defect in Si or SiO2; in particular, it is totally unlike the common E′ center of SiO2. In contrast to Qss, both Pb and Nst were found to be greatly reduced by steam oxidation and hydrogen annealing. Both Pb and Nst may be regenerated by subsequent N2 anneals at 500 °C. In a graded series of samples, Pb and Nst are found to be proportional and nearly equal in concentration. This possible confirmation of SiIII at the interface, and correlation with Nst, support the theoretical indication of an SiIII b...
394 citations
TL;DR: In this paper, the capacitance-vs-voltage characteristics of ZnO varistors which contain rare earth metal oxides and cobalt oxide were studied on the basis of the symmetrical Schottky-barrier model of the grain boundary region.
Abstract: Studies were made on the capacitance‐vs‐voltage characteristics of ZnO varistors which contain rare‐earth metal oxides and cobalt oxide. On the basis of the symmetrical Schottky‐barrier model of the grain‐boundary region, the barrier height φ and donor concentration Nd of ZnO grains were obtained by the modified 1/C2‐V plot reduced from observed C‐V relations. φ and Nd were obtained as 0.72 V and 1.6×1018 cm−3, respectively, for a ZnO‐Pr6O11‐Co3O4 system and 1.00 V and 0.76×1018 cm−3, respectively, for a ZnO‐Pr6O11‐La2O3‐Co3O4 system. These results support the validity of this model and the treatment.
386 citations
TL;DR: In this paper, the transition to single crystal of ion-implanted amorphous Si and Ge layers is described in terms of a liquid phase epitaxy occurring during pulsing-laser irradiation.
Abstract: The transition to single crystal of ion‐implanted amorphous Si and Ge layers is described in terms of a liquid‐phase epitaxy occurring during pulsing‐laser irradiation. A standard heat equations including laser light absorption was solved numerically to give the time evolution of temperature and melting as a function of the pulse energy density and its duration. The structure dependence of the absorption coefficient and the temperature dependence of the thermal conductivity were accounted for in the calculations. In this model the transition to single crystal occurs above a well‐defined threshold energy density at which the liquid layer wets the underlying single‐crystal substrate. Experiments were performed in ion‐implanted amorphous layers of thicknesses ranging between 500 and 9000 A. The energy densities of the Q‐switched ruby laser ranged between 0.2 and 3.5 J/cm2; time durations of 20 and 50 ns were used. The experimental data are in good agreement with the calculated values for the amorphous thickness–energy−density threshold. The model deals mainly with plausibility arguments and does not account for processes occuring in the near‐threshold region or below the melting temperature.
352 citations
TL;DR: In this article, the experimental dependence of electron mobility and free-carrier absorption on temperature and/or on carrier concentration can be consistently explained only when the effect of compensation is quantitatively taken into account.
Abstract: Theoretical and experimental studies of the electron mobility and the free‐carrier absorption of n‐type InP were carried out in the temperature range 77–300 °K. All major scattering processes and screening effects were taken into consideration. It was found that the experimental dependence of electron mobility and free‐carrier absorption on temperature and/or on carrier concentration can be consistently explained only when the effect of compensation is quantitatively taken into account. Convenient procedures are presented for the determination of the compensation ratio from the values of electron mobility and from the free‐carrier absorption coefficient. The high contribution of optical‐phonon scattering in InP limits the applicability of the free‐carrier absorption approach to electron concentration n≳1017 cm−3. Electron mobility, however, can be reliably employed for the determination of the compensation ratio for n≳1017 cm−3 at 300 °K and n≳1015 cm−3 at 77 °K.
TL;DR: In this article, the transverse mechanical resonant frequencies of cantilever beams have been used to calculate Young's modulus of the insulating thin films, which is applicable to a wide range of materials and deposition procedures.
Abstract: Electrostatically deflectable cantilever beams (1000–9000 A thick, 120–8.3 μm long) have been fabricated from a number of thin insulating films prepared by a variety of deposition methods. Measurements of the transverse mechanical resonant frequencies of these beams have been used to calculate Young’s modulus of the insulating thin films. This new technique is relatively simple and accurate and is applicable to a wide range of materials and deposition procedures.
TL;DR: In this paper, the authors studied the piezoelectric properties of PZT ceramics and polymers including polyvinylidene fluoride (PVDF), polyethylene (PE), and polyvinylon alcohol (PVA).
Abstract: Piezoelectric properties have been studied for the composite systems of PZT ceramics and polymers including polyvinylidene fluoride (PVDF), polyethylene (PE), and polyvinyl alcohol (PVA). The values of the piezoelectric constants and their temperature and frequency dependences were discussed on the basis of the theoretical expressions of the piezoelectric constants for a two‐phase system with piezoelectric spherical dispersions. The piezoelectric activity of all the composite systems studied was mainly ascribed to the piezoelectricity of PZT ceramics. For the PVDF‐PZT system, the piezoelectricity of PVDF was shown to make minor contribution compared to that of PZT ceramics. For the PE‐PZT system, the temperature dependence of the d constant due only to elastic relaxation in the PE phase was investigated. For the PVA‐PZT system, the retardational and relaxational frequency dependence of the d constant observed above 80 °C were successfully accounted for in terms of the interfacial and electrode polarizatio...
TL;DR: In this paper, the authors carried out a detailed study of catastrophic degradation in DH laser material from which they reached two conclusions: local melting occurs and is due to intense nonradiative recombination of minority carriers at a cleaved surface or at a defect.
Abstract: We carry out a detailed study of catastrophic degradation (CD) in DH laser material from which we reach two conclusions. First, local melting occurs and is due to intense nonradiative recombination of minority carriers at a cleaved surface or at a defect. The minority carriers are generated by absorbed superradiant light. Second, the dark line associated with CD results from propagation of a molten zone confined to the active layer. It is recrystallized epitaxially after the laser pulse but remains highly nonradiative because large numbers of point defects and dislocation loops are quenched into this region during rapid cooling from the molten state. Catastrophic damage was induced by exciting superradiance in the DH material with a cavity‐dumped Ar‐ion laser. The melting and recrystallization were established by observing a redistribution of Ga and Al in the x=0.08 active layers by TEM studies. The point defects were detected by scanning junction photocurrent measurements, electron‐beam‐induced current, ...
TL;DR: In this article, an analytical formula is derived to calculate the inductance of a finite-width superconducting strip transmission line, where the aspect ratio (the ratio of the linewidth to the insulation thickness) exceeds about unity.
Abstract: An analytical formula is derived to calculate the inductance of a finite‐width superconducting strip transmission line. The formula gives an accurate inductance value when the aspect ratio (the ratio of the linewidth to the insulation thickness) exceeds about unity.
TL;DR: The spectral dependence of the absorption coefficient of silicon for photon energies up to 2.7 eV was determined for several temperatures in the range 298-473 K as discussed by the authors, where the effect of a temperature increase appears as a red shift of the spectrum.
Abstract: The spectral dependence of the absorption coefficient of silicon for photon energies up to 2.7 eV was determined for several temperatures in the range 298–473 K. The effect of a temperature increase appears as a red shift of the absorption spectrum. The magnitude of the shift is larger than that of the fundamental energy gap, increases with increasing photon energy in the range 1.1–1.7 eV, and is constant for energies greater than 1.7 eV. A phenomenological expression deduced by analysis of the data may be used to calculate α (E) at elevated temperature, given α (E) at room temperature. The reflectance was also measured at 299, 413, and 516 K in the photon energy range 2.5–3.8 eV.
TL;DR: In this paper, the effective elastic moduli of randomly oriented aggregates of orthorhombic crystals have been derived using the variational principles of Hashin and Shtrikman.
Abstract: Bounds on the effective elastic moduli of randomly oriented aggregates of orthorhombic crystals have been derived using the variational principles of Hashin and Shtrikman. The bounds are considerably narrower than the widely used Voigt bound and Reuss bound. In many instances, the separation between the new bounds is comparable to, or less than, the uncertainty introduced by experimental errors in the single‐crystal elastic stiffnesses. The Voigt‐Reuss‐Hill average lies within the Hashin‐Shtrikman bounds. several percent.
TL;DR: In this article, the electron trapping behavior of SiO2 has been measured as a function of thickness at 295 and 77 °K, and the results indicate bulk traps are dominant at 295 K and traps associated with the Si•SiO2 interface are dominant in 77 Ã 0 K. These observations have been verified using a photo I•V technique.
Abstract: The electron trapping behavior of SiO2 has been measured as a function of thickness at 295 and 77 °K. The devices used were metal‐oxide‐semiconductor devices with the SiO2 grown thermally. The results indicate bulk traps are dominant at 295 °K and traps associated with the Si‐SiO2 interface are dominant at 77 °K. The effect of processing conditions was also studied and the optimum conditions are different for the two temperatures used for the measurements. These observations have been verified using a photo I‐V technique. The generation of donor states in the SiO2 near the Si‐SiO2 interface was observed as a result of the electron current through the SiO2.
TL;DR: In this article, the problem of film-edge-induced stress in substrates has been analyzed self-consistently by allowing a distributed force in the film, which arises from the relaxation of the film strain, which is complementarily coupled to the substrate strain under the film force.
Abstract: The problem of film‐edge‐induced stress in substrates has been analyzed self‐consistently by allowing a distributed force in the film. The distributed force arises from the relaxation of the film strain, which is complementarily coupled to the substrate strain under the film force. The results are compared to those from a concentrated‐edge‐force approximation.
TL;DR: In this paper, the Boltzmann equation for the electron energy distribution was used to calculate α and η, the ionization and attachment coefficients, and (E/N) *, the limiting breakdown electric field to gas density ratio, in SF6 and SF6 mixtures.
Abstract: We have calculated α and η, the ionization and attachment coefficients, and (E/N) *, the limiting breakdown electric‐field–to–gas‐density ratio, in SF6 and SF6 mixtures by numerically solving the Boltzmann equation for the electron energy distribution. The calculations require a knowledge of several electron collision cross sections. Published momentum transfer and ionization cross sections for SF6 were used. We measured various attachment cross sections for SF6 using electron‐beam techniques with mass spectrometric ion detection. We determined a total cross section for electronic excitation of SF6 by comparing the predicted values of α, η, and (E/N) * with our measured values obtained from spatial current growth experiments in SF6 in uniform fields over an extended range of E/N. With this self‐consistent set of SF6 cross sections, together with published He and N2 cross sections, it was then possible to predict the dielectric properties of SF6‐He and SF6‐N2 mixtures. Published experimental values of α for the SF6‐He mixtures lie between the values of α calculated with and without ionization of SF6 by excited He atoms. Published experimental values of (E/N) * agree with our calculations to within 5% in both the SF6‐He and the SF6‐N2 mixtures.
TL;DR: In this paper, the authors investigated the effect of laser-induced stress wave environments generated at a confined surface by a pulsed laser, and showed that the impact of the ionized plasma created near the metal surface on the induced stress wave was negligible.
Abstract: Stress‐wave environments generated at a confined surface by a pulsed laser were investigated. Experimental measurements and theoretical calculations demonstrated that confinement of the surface with a transparent overlay provided an effective method of generating high‐amplitude laser‐induced stress waves in the target material. Peak pressures aproaching 10 GPa were possible at laser power densities of several times 109 W/cm2 for laser pulse durations ranging from several nanoseconds to several tens of nanoseconds. These pressures were generated in an air environment at standard conditions, thus enhancing their practical utilization for processing of materials and measurments of material properties. At laser power densities greater than 109 W/cm2, the laser‐induced stress‐wave environment was controlled by properties of the ionized plasma created near the metal surface. Some enhancement in the amplitude and duration of laser‐induced stress‐wave environments was observed at laser power densities less than 109 W/cm2 if low thermal conductivity and low heat of vaporization materials were used. Calculations show that peak pressures greater than 10 GPa were possible by superimposing stress waves either through reflection off a high acoustic impedance barrier or through the interaction of stress waves which were generated at different surfaces of a material.
TL;DR: In this article, the infrared spectra representative of crystalline regions of cast films of phase-III poly(vinylidene fluoride) (PVF2) have been obtained by absorbance subtraction techniques using a FT-IR instrument.
Abstract: Infrared spectra representative of crystalline regions of cast films of phase‐III poly(vinylidene fluoride) (PVF2) have been obtained by absorbance subtraction techniques using a FT‐IR instrument. The spectra contain more bands than previously reported and are not consistent with current models for the crystal structure. Several possible models and their relationship to the corresponding crystalline spectra of phase II and phase I are discussed.
TL;DR: In this article, the ferroelectric domain in Ti-diffused c-plate LiNbO3 optical waveguides was examined by chemical etching and a plausible explanation for the domain inversion was considered.
Abstract: The ferroelectric domain in Ti‐diffused c‐plate LiNbO3 optical waveguides were examined by chemical etching. In the Ti‐diffused +c layer, a domain‐inversion layer was formed where the spontaneous polarization is opposite to that of the substrate. The formation is dependent upon diffusion conditions. On the other hand, no domain inversion appeared in the diffused −c layer. It is concluded that the −c face is quite favorable for fabricating Ti‐diffused c‐plate optical waveguide for application in electro‐optic devices. A plausible explanation for the domain inversion is considered.
TL;DR: In this paper, the authors interpreted the absorption of AlN thin films as excitonic absorptions due to transitions across the direct energy gap of about 6.2 eV and 7.8 eV.
Abstract: Optical absorption of AlN thin films shows a ’’knee’’ structure at 6.2 eV and an intense band at 7.8 eV. The structure at 6.2 eV is interpreted as excitonic absorptions due to transitions across the direct energy gap of about 6.2 eV. Dichroism observed at the absorption edge indicates that the transition Γ1v–Γ1c (E∥c) is of lower energy than the transition Γ6v–Γ1c (E⊥c). Strong dichroism in the 7–8‐eV region is thought to cause the birefringence of AlN.
TL;DR: In this paper, the structure of the particles was very disordered at sizes ≲100 A but changed to become single crystal with a disordered core as the size increased to 100-200 A.
Abstract: Colloidal iron dispersions have been prepared by the thermolysis of Fe(CO)5 in solutions of functional polymers. The structure of the particles was very disordered at sizes ≲100 A but changed to become single crystal with a disordered core as the size increased to 100–200 A. Particles ≲100 A were superparamagnetic, and particles in the 100–200‐A range had a time‐dependent hysteresis. On exposure to the atmosphere an ∼30‐A‐thick γ‐Fe2O3 oxide film was produced on the surface of the particles. This is the ’’passive oxide film’’ detected previously by a number of techniques but never before imaged directly in situ. As water was absorbed from the atmosphere the chlorinated solvent‐based dispersions reacted further to give β‐FeOOH. This reaction was promoted by chloride‐ion impurity. The magnetic moment decayed with oxidation roughly in proportion to the quantities of Fe, γ‐Fe2O3, and β‐FeOOH present. Disorder in the structure of ≲100‐A particles formed in nonchlorinated solvent‐based dispersions produced an i...
TL;DR: In this article, a focused ion-beam sputtering technique was used to sample lead zirconate titanate (ZrxTi1−x)O3 in an O2 atmosphere.
Abstract: Lead zirconate titanate is a solid solution with nominal composition Pb(ZrxTi1−x)O3. Ferroelectric thin films of this material have been successfully deposited by a focused ion‐beam sputtering technique in an O2 atmosphere. These films were characterized according to composition, crystal structure, and dielectric and ferroelectric properties. The effects of deposition temperature, heat treatment after deposition, and substrate and target material were investigated. The composition of the films was within 1 at.% of the composition of the multicomponent PZT target for substrate temperatures up to 200 °C. The Pb concentration decreased for substrate temperatures above 200 °C. Films deposited at substrate temperatures below 250 °C were microcrystalline. At 300 °C, the pyrochlore phase was obtained. Films with the ferroelectric perovskite structure were deposited above 400 °C, which is the lowest deposition temperature ever reported for this phase. O2 losses during postdeposition annealing resulted in a collap...
TL;DR: In this article, the growth rate of crystallization and the nucleation rate of amorphous silicon layers produced by evaporation were investigated. But the results of the analysis were limited to a single sample.
Abstract: Crystallization has been studied in amorphous silicon layers produced by evaporation. The crystalline fraction is deduced from conductivity measurements. Depending upon the conditions of evaporation homogeneous or heterogeneous nucleation is observed and the crystallization is induced at the surface or in the bulk. The variations with temperature of the growth rate of crystallization and of the nucleation rate are obtained from the kinetics of the crystallization measured at various temperatures. The results allow one to provide orders of magnitude for the thermodynamical parameters which characterize the crystallization.
TL;DR: In this paper, an isotropic compression of the unit cell was found in α•Al2O3 and α•Cr•O3 with the corundum structure.
Abstract: Accurate x‐ray diffraction experiments for hydrostatic compression of corundum α‐Al2O3 and transition‐metal sesquioxides with the corundum structure, V2O3, Cr2O3, and α‐Fe2O3, were performed using a cubic‐anvil type of high‐pressure apparatus at room temperature up to about 120 kbar. An isotropic compression of the unit cell was found in α‐Al2O3 and Cr2O3. In V2O3 and α‐Fe2O3, anisotropic behaviors of compression were observed: The ratio c/a in the hexagonal cell increases in V2O3 and decreases in α‐Fe2O3 with increasing pressure. The isothermal bulk modulus KT=1.75±0.03 Mbar of V2O3 is unusually small among the studied compounds with the corundum structure. Values of 2.39±0.04 Mbar and 2.31±0.05 Mbar were calculated for KT of α‐Al2O3 and Cr2O3, and a value of 2.31±0.10 Mbar for KT of α‐Fe2O3 in the pressure range below 30 kbar.
TL;DR: In this article, the interface state buildup in wetoxide MOS capacitors under positive bias was studied as a function of time following pulsed e −beam irradiation, and the buildup was found to be a two-stage process.
Abstract: The interface‐state buildup in wet‐oxide MOS capacitors under positive bias was studied as a function of time following pulsed e‐beam irradiation. The buildup was found to be a two‐stage process. The first stage, which occurs during the time required for holes to transport to the SiO2/Si interface, determines the final or saturation value of interface states and was found to be field dependent and temperature independent. The second stage, which begins after the holes have reached the SiO2/Si interface and continues for several thousand seconds, determines the time scale for the buildup and was found to be both field and temperature dependent.
TL;DR: In this paper, it was shown that there are large changes produced in both refractive indices n0 and ne by the energy deposited in nuclear collisions between the implanted ions and the lattice.
Abstract: Ion implantation is an attractive method for writing optical circuits for use in integrated optics. In LiNbO3 it is shown that there are large changes produced in both refractive indices n0 and ne by the energy deposited in nuclear collisions between the implanted ions and the lattice. The process is insensitive to ion species and at 300 K a universal curve exists for the decrease of n0 as a function of deposited energy by nuclear collisions. Saturation changes of −6% occur at 300 °K, and larger values are noted for 77 K implants. The saturation condition is reached after the deposition of ∼1022 keV cm−3 from the ion beams. Because the indices are reduced, ion beams have been used to write low index boundaries to define waveguiding regions. By using energetic light ions (e.g., 2‐MeV He+) negligible change is produced in the surface layer where the energy loss is primarily electronic and thus the low index region is formed deep within the solid. The computed and measured mode characteristics are in good ag...