摘要:

The properties of consecutive energy‐barrier systems are derived from the basic principles of deformation kinetics and from the rate theory as applied to plastic flow. It is shown that these properties are functions of well‐defined relations between the activation energy and volumes of the different barriers. In particular, for a system of two consecutive energy barriers, it is shown that the usual equation used to calculate the strain rate ?=&egr;0/(t1+t2), wheret1andt2are two waiting times, is only an approximation valid when backward activations are negligible. The behavior of materials, in which plastic flow is controlled by a system of two consecutive energy barriers, was determined rigorously for various experimental conditions. It is shown that the calculated temperature dependence of the flow stress as well as the stress and temperature dependence of the experimental activation volume and strain‐rate sensitivity that follow from the properties of consecutive energy barriers are in agreement with experimental observations.

ISSN:0021-8979    

DOI:10.1063/1.325404

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A modified lattice‐statics method to calculate the atomic displacements associated with a screw dislocation is outlined. The model incorporates an anharmonic region wherein the forces are derived from a pair potential. Appropriate energy and force expressions are derived. The modifications necessary for the implementation of the conjugate‐gradient function minimization method are also derived.

ISSN:0021-8979    

DOI:10.1063/1.325405

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The atomic structure of a ⟨110⟩ screw dislocation core in aluminum is calculated by the modified lattice‐statics method developed in the preceding paper. The method includes anharmonic as well as harmonic forces and permits relaxation of the atoms in all three dimensions. All forces used in the present calculations were derived from a first‐principles interatomic pair potential obtained via pseudopotential theory. Several significant differences from the ordinary lattice statics results are noted, including the displacement field, Peierl’s energy barrier, and the equilibrium core‐center location.

ISSN:0021-8979    

DOI:10.1063/1.325326

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The pseudopotential of gold using Harrison’s modified point‐ion form has been calculated by fitting with the experimental elastic data and is compared with the pseudopotential curve obtained from the Fermi surface data. This pseudopotential has been used to calculate the third‐order elastic constants of gold.

ISSN:0021-8979    

DOI:10.1063/1.325406

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

In certain mixtures of nematic and cholesteric liquid crystals, it is found that the metastable final state in an electric‐field‐induced nematic to cholesteric transition depends on the turnoff rate of the applied voltage. Experimental evidence sugests that two processes, i.e., helix winding and Freedericksz transition type molecular reorientation, may be involved. Relaxation times for both are estimated theoretically and compared with experimental results. An overall relaxation process is also proposed phenomenologically and the predictions compare favorably with the temporal data. The prerequisites on the threshold fields and relaxation times for this phenomenon are deduced. It is believed that this new observation may help explain the transient behavior in a nematic‐cholesteric phase transition and may promise some practical applications.

ISSN:0021-8979    

DOI:10.1063/1.325407

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Anderson has derived an equation describing the temperature dependence of bulk moduli of oxide solids using the Mie‐Gru¨neisen equation of state. In this paper, we have shown that this equation can be applied to all solids in general, without restricting the applicablity to oxides alone. In our approach, use has been made of the Mie‐Gru¨neisen equation of state and an assumption that the main change in bulk modulus with temperature arises from the associated volume change and the volume changes encountered are small, which is true in many solids. We have estimated the values of bulk moduli of many nonoxide solids like Au, Ag, Cu, Si, PbSe, Mg2Sn, and MgCu2, which agree well with the experimentally determined values. The Debye characteristic temperature, the Gru¨neisen parameter, and the Anderson‐Gru¨neisen parameter have been considered to be temperature dependent.

ISSN:0021-8979    

DOI:10.1063/1.325408

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

It is demonstrated how a quantitative study of some anomalous thin‐foil annealing phenomena, if interpreted correctly, leads to the determination of important physical constants. The necessary theory is developed and applied to measure the activation energy for dislocation pipe diffusion in thin aluminum foils from the annealing rate of quenched‐in and subsequently truncated faulted dislocation loops. The results are compatible with those obtained from void annealing by another group. Triangular faulted defects present in bulk‐aged and thinned samples of aluminum are shown to consist of a mixture of extrinsic and intrinsic loops. They can readily be distinguished by their annealing rates. From the relative values of these rates, the relation between the intrinsic and extrinsic stacking‐fault energies has been determined.

ISSN:0021-8979    

DOI:10.1063/1.325355

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Thermally deposited silicon films doped with oxygen atoms and used as passivation films on silicon devices have been studied with transmission electron microscopy, x‐ray diffraction, and ESCA. The films contain at least two phases, silicon microcrystals and silicon oxide. The size of the microcrystals in as‐deposited films was dependent both on the deposition temperature and on the oxygen concentration. Heat treatment caused crystal growth which depended mainly on the annealing temperature and weakly on the annealing time. The lattice constant of the microcrystals was directly related to their size. The silicon oxide phase in as‐deposited films was found to be SiO1.4. The results suggest ’’mosaic’’ model of the films which are amorphous when the diameter of the silicon microcrystals was less than 10 A˚.

ISSN:0021-8979    

DOI:10.1063/1.325356

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A model is presented for the description of thin films prepared from solution by spinning. Using only the centrifugal force, linear shear forces, and uniform evaporation of the solvent, the thickness of the film and the time of drying can be calculated as functions of the various processing parameters. The model is compared with experimental results obtained on positive photoresists and excellent agreement is obtained. When adequate care are is taken, the liquid forms a level surface during spinning, and the film thickness becomes uniform and independent of the size of the substrate. The film thicknesshshows the following dependence on spin speedf, initial viscosity &ngr;0, and evaporation ratee:h∝f−2/3&ngr;o1/3e1/3, andeis proportional tof1/2.

ISSN:0021-8979    

DOI:10.1063/1.325357

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Platinum silicide is widely used to make Ohmic contacts and Schottky‐barrier diodes. These contacts are formed by evaporation of platinum on a (001) silicon substrate. During evaporation, two phases are formed: Pt2Si and/or or PtSi, depending on the process used. After sintering, the final phase is PtSi. This study shows that PtSi grains in epitaxy on (001) silicon are oriented along two separate sets of orientation: the already known (11¯0) and a newly determined (12¯1) orientation. The ratio of the number of grains oriented along the latter and former orientations depends on the wafer temperature during evaporation. The two orientations may be caused by two different formation mechanisms: evaporation on silicon substrates at 320 °C under which Pt2Si is formed at first and then transformed into the PtSi phase with the (11¯0) orientation during sintering and evaporation on silicon substrates at 400 °C under which PtSi is formed directly along the (12¯1) plane and undergoes no change during further heat treatments. For intermediate temperatures, both mechanisms are present.

ISSN:0021-8979    

DOI:10.1063/1.325358

出版商:AIP    

年代:1978

数据来源: AIP