摘要:

We have characterized the electrical transport properties of neutron‐transmutation‐doped polycrystalline silicon. Zero‐bias measurements of resistance have been made as a function of temperature on both bulk specimens and individual grain boundaries in this material. Below a doping level of ∼2×1015phosphorus/cm3, the bulk resistance has a nearly Arrhenius behavior with an activation energy of ∼0.55 eV; above this donor concentration the resistivity is markedly curved on an Arrhenius plot with values of slope which decrease with decreasing temperature. Potential probe measurements show that a large spread in grain‐boundary impedances exist in these higher‐doped specimens. We compare our data to theoretical expressions for current flow across grain‐boundary potential barriers and good agreement is observed; these comparisons indicate that the largest grain‐boundary state densities observed in our samples consist of ∼6×1011available single‐electron‐states/cm2located within ∼0.2 eV from the center of the forbidden gap. The chemical potential of these grain‐boundary regions is found to lie at midgap, in agreement with previous data on thin‐film polycrystalline silicon. We note that the considerably higher orientation‐independent state densities found in thin‐film polycrystalline silicon contrasts strongly with the present data and suggest the presence of serious contamination effects in previously studied material.

ISSN:0021-8979    

DOI:10.1063/1.325394

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A technique is described for applying flexible boundaries to an atomic region in computer simulation of dislocations or other line defects. The method results in continuity of equilibrium, under the chosen interatomic potential, across the interface between the atomic region and the outer region described in terms of anisotropic elastic continuum solutions. The technique has high numerical efficiency. It is shown that when the crystal is initially dislocated according to the Volterra solution for displacements, the finite strains give rise to geometrical nonlinear effects, usually disregarded in linear elasticity, which contribute to a volume change of the crystal. Allowance for this effect, and for elastic nonlinearity in the crystal beyond the boundary region, allows the overall dilatation of a finite body due to the dislocation to be rigorously computed. For illustration of the geometric nonlinear effect, and for comparison with earlier modeling methods, examples of computations are given for the [100] edge dislocation in &agr; iron.

ISSN:0021-8979    

DOI:10.1063/1.325395

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

n‐GaAs substrates of varying doping levels were implanted with presumably electrically inactive ions like H, B, and As, and then annealed at high temperatures. Several experimental techniques were employed to detect and estimate the compensation in the implanted layers. We found the compensation in the proton‐implanted layers is alone dependent on the initial doping level of the substrate, while it is related to the ion introduced in the boron‐ and arsenic‐implanted layers. Along with these results, we present and discuss the preliminary results of the photoluminescence measurements performed to investigate the nature of the defects responsible for compensation.

ISSN:0021-8979    

DOI:10.1063/1.325396

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Amorphous layers, approximately 4000 A˚ thick, were formed on single‐crystal Si samples by implantation of28Si ions at LN2substrate temperature. Channeling‐effect measurements with MeV4He ions were used to measure the thickness of the amorphous layers and to measure the subsequent epitaxial regrowth on the underlying crystalline substrates. For annealing temperatures between 450 and 575 °C, the growth rate showed a strong dependence on the substrate orientation with ⟨100⟩‐oriented samples exhibiting about a 25 times higher growth rate than ⟨111⟩‐oriented samples. Measurements of the growth rate on a series of samples cut in 5° angular increments show that there is a monotonic decrease from the ⟨100⟩ to the ⟨111⟩ orientation. A simple model is proposed to explain the observed orientation dependence.

ISSN:0021-8979    

DOI:10.1063/1.325397

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Transmission electron microscopy has been used to study the effects of high‐power laser pulses on as‐grown and boron‐implanted silicon. No defects (dislocations, dislocation loops, and stacking faults) were observed in either as‐grown or boron‐implanted (doses 3×1015and 2×1016ions cm−2) silicon after pulsed laser treatment. In thermally annealed specimens, on the other hand, a significant amount of damage was retained even after annealing at 1100 °C for 30 min. After thermally annealing the implanted laser‐treated specimens at 600 and 900 °C for 30 min, no defects were observed for low‐dose specimens; however, in high‐dose specimens, precipitation of boron occurred after 600 °C annealing and it increased after annealing at 900 °C. These results and the electrical measurements on these samples suggest that the boron atoms in the precipitates are electrically inactive.

ISSN:0021-8979    

DOI:10.1063/1.325398

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Implantation of group‐III and group‐V ions along [111] and [110] axes of silicon have been performed using a backscattering technique, and the depth profiles of implanted ions have been measured by theC‐Vmethod. The range of channeled Ga ions is the largest among the present data, and ap‐type layer of about 6 &mgr;m is obtained by implantation at only 150 keV. The carrier profiles of channeled Al and Ga ions with deep ranges do not show any distinguishable channeled peak contrasting with the B, P, and As channeling which gives a well‐defined peak. The electronic stopping cross section (Se) of channeled P ions agree well with the results of Eisen and Reddi, but in B channeling, the discrepancies of 10–20&percent; are observed amongSevalues obtained experimentally by three different groups.

ISSN:0021-8979    

DOI:10.1063/1.325399

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The study of the spatial coherence properties of light scattered by ultrasound‐produced rolls in MBBA allows one to obtain information on the hydrodynamics of the process. In particular, the correlation lengthlnof refractive‐index fluctuations is first found to increase and then to decrease with the voltageVapplied to the piezoelectric transducer. The onset of ’’turbulent’’ motion is clearly visible at the voltage at whichdln/dVchanges sign.

ISSN:0021-8979    

DOI:10.1063/1.325400

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A theoretical heat flow analysis for horizontal ribbon growth is presented. Equations are derived relating pull speed, ribbon thickness, thermal gradient in the melt, and melt temperature for limiting cases of heat removal by radiation only and isothermal heat removal from the solid surface over the melt. Geometrical cross sections of the growth zone are shown to be triangular and nearly parabolic for the two respective cases. Theoretical pull speed for silicon ribbon 0.01 cm thick, where the loss of latent heat of fusion is by radiation to ambient temperature (300 K) only, is shown to be 1 cm/sec for horizontal growth extending 2 cm over the melt and with no heat conduction either to or from the melt. Further enhancement of ribbon growth rate by placing cooling blocks adjacent to the top surface is shown to be theoretically possible.

ISSN:0021-8979    

DOI:10.1063/1.325401

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Recent studies of shock propagation in a one‐dimensional discrete crystal lattice are extended to include the case for which the lattice is at a nonzero intitial temperature. The lattice is assumed to be monatomic, and its atoms are assumed to interact via a Morse‐type interatomic potential. Behind the shock front, a spectrum of well‐defined stable pulses (solitons) is observed to propagate amid the thermal background of the lattice. The solitons have varying amplitude and propagation velocities, and the different velocities introduce a spreading effect which prevents the shock profile from approaching a steady state. The velocity distribution function of atoms well behind the front is calculated and indicates an approach to thermal equilibrium at an elevated temperature in this region of the crystal. The implications of the nonsteady behavior and the slow approach to thermal equilibrium for currently used theories of detonation are noted and discussed.

ISSN:0021-8979    

DOI:10.1063/1.325402

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A differential‐path ultrasonic technique is used to obtain the acoustic propagation characteristics of shear waves in polymethyl methacrylate (PMMA) and Epon 828‐Z. The acoustic velocity and attenuation are measured at 0.5, 1, and 2 MHz over a temperature range of −60 to 70 °C. Time‐temperature superposition is used to transform these data into their ’’master curve’’ form. Using this representation, the shear‐stress relaxation modulus is then deduced and combined with the previously determined longitudinal data to form a complete characterization of the short‐time linear response of these two homogeneous and isotropic viscoelastic polymers.

ISSN:0021-8979    

DOI:10.1063/1.325403

出版商:AIP    

年代:1978

数据来源: AIP