摘要:

A constitutive equation for porous materials capable of supporting deviatoric stresses is described. The model incorporates the deviatoric stresses in a physically consistent manner so that the porosity is a function of the complete stress tensor and such phenomena as shear‐enhanced pore compaction may be represented. The constitutive equation is based on the physical concept of a closed yield surface in stress space which varies as the material porosity changes. An example of the application of the model to 22% porous 2024 aluminum is given.

ISSN:0021-8979    

DOI:10.1063/1.327983

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Pressures assigned to the semiconductor‐metal transitions in ZnTe, ZnS, GaAs, and GaP have been determined by detecting the electrical resistance change of the semiconductors while the lattice parameter of standard material NaCl was simultaneously measured with x‐ray diffraction techniques. A pressure vessel of the split‐octahedron type and various pressure‐transmitting media have been employed. Pressures were estimated according to the equation of state for NaCl proposed by Decker. The transition pressures, 1296 kbars for ZnTe, 1557 kbars for ZnS, 1888 kbars for GaAs, and 25310 kbars for GaP, constitute fixed points for pressure calibration above 100 kbars at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.327984

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Measurements have been made of the value (∂T/∂P)sas a function of pressure up to 32 kbar, at room temperature (296.7 °K), for cerium through its electronic transition at 7.5 kbar. The thermodynamical Gru¨neisen parameter is calculated using the thermodynamic relation &ggr;th=(Bs/T) (∂T/∂P)s, whereBsis the adiabatic bulk modulus. An anomalous increase of &ggr;thin the low‐pressure phase and a rapid decrease after the transition are obtained for cerium.

ISSN:0021-8979    

DOI:10.1063/1.327985

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The reacton of hydrogen with hydroxyl‐free vitreous silica has been measured for temperatures between 500 and 850 °C, pressures between 0.132 and 5.78 atm, and sample thicknesses between 0.057 and 1.06 cm. The results can be explained by a simple model often used to explain tarnishing reactions. This model assumes that the reaction rate is very fast compared to diffusion, and that a fixed concentration of trapping sites exists in the specimen.

ISSN:0021-8979    

DOI:10.1063/1.327986

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A new method to analyze 1st‐ and 2nd‐order reaction rate curves as appearing in, e.g., thermal desorption and thermoluminescence is described. It is based on the concept of the ’’characteristic time’’ &psgr; of the process. It is shown that for constant temperature and hyperbolic heating schedules, the reaction rate depends on &psgr; only, while for the linear temperature sweep there is also a slight dependence onE/kTmwithTmbeing the peak temperature. The method is based on these facts, and, contrary to previous methods, makes use of all experimental data points, yielding both activation energy and frequency factor. The new method is demonstrated for a thermal desorption and a thermoluminscence peak.

ISSN:0021-8979    

DOI:10.1063/1.327987

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The effects upon the drift velocity and electron temperatures in silicon inversion layers due to interfacial polar‐mode phonons in the Si/SiO2interface have been calculated at various temperatures. These calculations were carried out at 77, 150, and 300 K using a three‐energy‐level model for transport in the quasi‐two‐dimensional inversion layer assuming a drifted‐Maxwellian distribution. The effects of the polar interface phonon scattering are compared to the effects of scattering due to Si bulk phonons, interface charges, and interface roughness. The effects of the remote phonons are found to be small in the drift velocity, but are significant as an energy relaxation mechanism at high fields and large inversion densities.

ISSN:0021-8979    

DOI:10.1063/1.327988

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

It is proposed that roughening models of the solid/liquid interface in pure systems should be modified to require a minimum degree of clustering among solid states and among liquid states. An approximate treatment is developed in terms of a minimum cluster size and applied as an amendment to the Temkin treatment. The effect on the anisotropy of the interfacial free energy is presented as a function of the entropy of melting of the substance, the minimum cluster size, and the interface orientation parameters. It is concluded that roughening effects eliminate cusps in the &ggr; plot for planes of comparatively high Miller indices and enshallow the cusps of planes of low Miller indices.

ISSN:0021-8979    

DOI:10.1063/1.327989

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The surface chemistry of silicon exposed to reactive XeF2gas and the chemisorption of SiF4on Si at −150 and 25 °C have been studied using XPS and AES. While SiF4can be condensed at −150 °C, XeF2is dissociatively chemisorbed and Xe does not stick on the surface. For both Si/SiF4and Si/XeF2at 25 °C, a layer of SiF2‐like surface species is identified from the characteristic core level chemical shifts. The formation of this fluorinated surface layer hinders the adsorption of SiF4, but XeF2reacts with this layer to form volatile SiF4. The behavior of fluorine chemisorption on silicon is illustrated for the first time and the role of surface fluorine in the silicon etching process is discussed in light of the new results.

ISSN:0021-8979    

DOI:10.1063/1.327990

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The chemisorption of oxygen on clean polycrystalline indium surfaces is investigated by the combined techniques of x‐ray photoelectron spectroscopy (XPS) and the static mode of secondary ion mass spectroscopy (SIMS). Oxygen uptake is characterized by a moderately rapid formation of In2O3, with no preoxidation adsorbed O2phase discernable in the XPS spectra. A high binding energy O (1s) peak becomes prominent after one monolayer of In2O3has formed, which we ascribe to adsorbed oxygen on the oxide. Formation of In2O3continues into the bulk either via migration of the adsorbed oxygen through the oxide layer to the metal‐In2O3interface or by the outward migration of indium cations to the surface. Both the formation of oxide and the onset of adsorption are reflected in the secondary ion yield ratios InO−2/InO−and O−2/O−. The behavior of SIMS molecular cluster ion yields with oxygen exposure are consistent with recent theoretical calculations of the cluster formation process, in which considerable local atomic order of the surface is present in the cluster.

ISSN:0021-8979    

DOI:10.1063/1.327991

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The epitaxial regrowth of argon‐implanted self‐implantation‐produced amorphous silicon underQ‐switched ruby laser pulses is reported. It is shown that pulse annealing succeeds in producing epitaxial regrowth in the present case where equilibrium thermal annealing fails. A highly porous layer filled with spherical voids is observed by transmission electron microscopy (TEM). Four‐point probe measurements of the annealed layers exhibit a very high sheet resistance. The electrical properties are explained in terms of the unique microstructure of the pulse annealed layer.

ISSN:0021-8979    

DOI:10.1063/1.327992

出版商:AIP    

年代:1980

数据来源: AIP