摘要:

Thermal phonon radiators allow short pulses of incoherent thermal phonon beams to generate in a simple manner and the center frequency of the broad frequency distribution of the emitted phonons to vary up to the acoustic cutoff frequencies. This paper reports experimental investigations of the connection between radiation temperature and radiation power using films of several metals (copper, nickel, gold, and lead) as phonon radiators on diamond. The measured dependencies of the radiation temperature on the radiation power show that the radiation process is by far better described by assuming acoustic mismatch between radiator and transmission medium than using the model of perfect match. Some metals on diamond give a phonon radiation power of several kilowatts per square millimeter radiator area. With a diamond substrate held at liquid‐helium temperature, a radiation temperature of a few hundred degrees Kelvin was achieved. If the phonon radiator deposited on diamond is immersed in liquid helium, the transport of heat to the liquid helium becomes important at radiation temperature below 30 °K and is dominant below 20 °K. This effect can be explained by assuming a thin vapor layer between the hot radiator and the liquid helium, and a gas kinetic energy transfer.

ISSN:0021-8979    

DOI:10.1063/1.1662498

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The problem of diffusion coefficients with fixed surface composition and variable diffusion coefficients is considered in the present paper. The rate of solute uptake or loss is given using the same equations as for constant diffusion coefficients taking the diffusion coefficient equal toD=approximately the first moment of the diffusion coefficient about the surface composition. When a new phase forms on the surface of the diffusion couple and it has a small composition range the rate of movement of the phase boundary is given by the same equations as for constant diffusion coefficients, but usingD¯, the weighted mean diffusion coefficient. As the composition range of the phase increases, the diffusion coefficient to be used deviates towards the value of the diffusion coefficient at the surface. The results are illustrated with calculated single‐and two‐phase composition profiles for carburization of a steel specimen.

ISSN:0021-8979    

DOI:10.1063/1.1662499

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A generalized two‐dimensional diffusion model has been developed which consists of an array of boundaries coupled to the free surface and to the substrate lattice. The model makes use of three nonlinear partial differential equations which describe lattice, grain boundary, and surface diffusion. This two‐dimensional model has been programmed for the IBM 360 computer using a finite‐difference solution to give concentrations as a function of time. An x‐ray intensity simulation program is developed to give integrated diffracted intensity for a given concentration distribution. This simulated intensity is compared with experimental intensity. Data are presented from a sample containing 8 &mgr; of Ni on a (111)‐oriented Cu crystal diffused for various times at 900°C and a similar sample with 6.5 &mgr; of Ni diffused at 600°C. The simulations are in good agreement with experimental intensity bands. Activation energies and frequency factors are given for volume and grain boundary diffusion which are in good agreement with those literature values that are available. After a diffusion treatment at 600°C, it was found that pipe diffusion makes an important contribution to the volume diffusion coefficient. At 900°C this does not appear to be true. The contribution from pipe diffusion correlates with rocking curve data except for compositions close to that of the free surface.

ISSN:0021-8979    

DOI:10.1063/1.1662500

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Surface morphology of the (0001) face of arsenic was characterized by the formation and growth of equilateral triangular and truncated triangular etch pits during free evaporation. The evaporation rate was correlated with observed changes in etch pit geometry and with the variation in intensity of a reflected gas‐laser beam. Experiments were supplemented by a computer simulation of free evaporation on the (0001) surface to provide a means for delineating the effect of the primary variables which control the morphology as well as the kinetic phenomena. The important controllable variables included the distribution between triangular and truncated forms, the growth rate, birth time, and the general geometric features of each pit. The birth time distribution strongly influenced the relationship between pit geometry and laser intensity. Other independent variables, such as the variation in the growth rate and degree of truncation, affected these quantities to a lesser extent.

ISSN:0021-8979    

DOI:10.1063/1.1662501

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Crystal quality during zone refining is usually poor. Owing to the great density of high‐diffusivity paths, solid‐state diffusion should not be neglected. Its influence on the concentration profile is described by experiment and theory. Since the concentration gradient and curvature become very large at the end of the bar (k<1), diffusion rates are especially high in this region. A successive separation of this enriched region may lead to a considerable improvement of zone refining. Theoretical and experimental results obtained with this method will be described.

ISSN:0021-8979    

DOI:10.1063/1.1662502

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The surface morphology of GaP liquid‐phase epitaxial layers has been studied for a wide range of growth conditions in order to determine the origin of the commonly observed corrugated or lamellar surface structure. A double slider apparatus was used for decanting the melts to preserve the high‐temperature morphologies and to permit controlled growth or meltback over selected areas of the substrate. The effect of melt supercooling was examined by varying the cooling rate and melt thickness. These results when combined with observations of the selected area meltback and regrowth experiments demonstrate that the lamellar morphology does not result from the action of capillarity forces on the last liquid to freeze or from interface instabilities associated with constitutional supercooling, as previously suggested. It is shown that the morphology is determined by the substrate orientation and is principally a manifestation of the microscopically layered nature of the liquid‐solid interface.

ISSN:0021-8979    

DOI:10.1063/1.1662503

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A work‐hardening model for ordered and disordered single‐crystalline alloys, where only one slip system is operative, is presented. The model is based on the experimental observation that most of the dislocations on parallel slip planes are locked as dipoles and this dipole formation is believed to be the principal source of work hardening. A detailed analysis of the behavior of passing dislocations is made as a function of frictional stress and vertical separation. Qualitative arguments for the observed strengthening in ordered and disordered alloys are presented based on the above analysis. The pronounced work hardening observed in ordered alloys is related to increased dipole strength as well as to reduced cross slip occasioned by atomic ordering.

ISSN:0021-8979    

DOI:10.1063/1.1662504

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A large defect ([inverted lazy s]600 &mgr; in diameter) was observed to move below the surface in aluminum thin film at a velocity in excess of 40 &mgr;/h (1.11×10−8m/sec). X‐ray stress topography was used to trace the migration, which was in the direction of electron flow, with dislocations in the silicon (under the aluminum) serving as location references for measuring the velocity. The migration direction and velocity of the subsurface defect were reproduced by forming an Al&sngbnd;Sn eutectic zone in the central part of an aluminum stripe. The movement of a liquid alloy inclusion in solid aluminum film under an electromigration driving force was proposed to explain the experimental observations.

ISSN:0021-8979    

DOI:10.1063/1.1662505

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Theory of the propagation of a surface wave related both to Bleustein‐Gulyaev waves and Love waves is developed. The wave has unidirectional particle motion perpendicular to the direction of propagation and parallel to the surface of a piezoelectric material which is covered with a finite‐thickness layer of an isotropic conducting material. An equation relating phase velocity to material costants is solved in closed form for a piezoelectric material of class 6mm, and conditions for the existence of various modes are presented. Piezoelectricity allows a nonleaky but dispersive wave to exist under conditions is which no love wave is possible, namely, when the shear wave velocity in the layer is greater than that in the substrate. Numerical results are presented for aluminium, gold, and zinc layers on PZT 4 ceramic.

ISSN:0021-8979    

DOI:10.1063/1.1662506

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Exposure of SiO2layers on silicon to a plasma environment during sputtering or backsputtering leads to degradation of the electrical properties of the interface. In this paper the effects of the ion bombardment occurring during such exposure are detailed. A low‐energy ion‐bombardment apparatus, capable of giving ion beams ranging from 100 nA at 10 eV to 5 &mgr;A at 3.0 keV of mass‐analyzed gas ions, constructed for this study, is described. Bombardment of SiO2layers by Ar+, N+, orN2+ions of any energy from 10 to 2800 eV leads to increase in interface state density and oxide interface charge. The oxide charge after bombardment is located both in the region of the Si/SiO2interface and in the outside 50 Å of the SiO2. Both induced oxide interface charge and interface state density increase linearly with dose to a saturation value, typically to 8×1012charges/cm2and 1013interface states/cm2eV at midgap after a dose of 8×1013ions/cm2at 600 eV, on 1000Å of SiO2. At constant dose the induced charge and interface state density increase linearly with energy to approximately 500 eV, then are independent of energy to the maximum energy studied. After ion bombardment to a dose of ions of 5×1013/cm2or greater, SiO2films exhibit a significant reduction in dielectric strength. This reduction is not completely recoverable by annealing to temperatures up to 600°C. Annealing to 600°C does, however, remove all interface charge, interface states, and room‐temperature trapping instabilities produced by the bombardment, as measured at room temperature after annealing. These experiments show that ion bombardment is capable of producing MOS degradation similar to some of the MOS degradation observed after sputter deposition of metals over oxide films. The increase in charge and interface states is a function of dose, so adjustment of plasma parameters during sputtering to give minimum ion bombardment should minimize this buildup of charge.

ISSN:0021-8979    

DOI:10.1063/1.1662507

出版商:AIP    

年代:1973

数据来源: AIP