摘要:

An acoustic densitometer has been developed for the precision measurement ofPVTdata over a wide range of temperatures and pressures. With this device, changes in the density of a solid or liquid are measured with a precision better than 3 parts in 105. Further, a density change of as much as 15% may be accommodated with no loss in the sensitivity or accuracy of the measurement. Finally, the electronic system used is straightforward, for which components are readily available. The system was tested on the polymer, polyethylene oxide, over a temperature range 10–50 °C and at pressures up to 1 kbar. Volume derivatives were obtained from the data and used to evaluate the Broadhurst‐Mopsik model for linear polymers. The agreement is good for temperatures up to and including 30 °C. In the temperature interval 40–50 °C, changes in the degree of crystallinity of the sample are suggested by the data.

ISSN:0021-8979    

DOI:10.1063/1.1662942

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

This paper describes a computer simulation experiment which reproduces, upon an idealized (100) cubic crystalline surface, the atomic processes occurring in condensation, evaporation, and surface diffusion. Nucleation of two‐dimensional clusters was observed. The equilibrium distribution of cluster sizes and the critical cluster size were measured for various parameter values and compared to predictions of the Walton‐Rhodin atomistic nucleation theory. Very good agreement between the simulation and theoretical values was obtained. The nucleation rate was also measured for one particular set of parameter values and found to agree satisfactorily with the atomistic theory prediction. Consequently, we conclude that the Monte Carlo method is suitable for the simulation of the phenomena of heterogeneous nucleation. Suggestions are offered for the refinement and extension of the simulation model for future simulation experiments to help answer the unresolved questions of heterogeneous nucleation theory.

ISSN:0021-8979    

DOI:10.1063/1.1663025

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A nonlinear theory is developed for electronic conduction in the presence of acoustic energy in piezoelectric semiconductors. The theory is valid for the cases of large acoustic energy and large electric field. The resulting expression is of closed form. The conductivities of acoustoelectric domains are measured. The experimental results are consistent with the theory if the domains are assumed to be composed of more than one acoustic frequency.

ISSN:0021-8979    

DOI:10.1063/1.1662953

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The scattering of Rayleigh waves by defects is discussed by means of first‐order perturbation theory. The defect is treated as a point defect of excess mass, either at the surface or some fixed distance below it. Scattering is into other Rayleigh waves or into bulk waves. Expressions are given for the scattering probability and for the relative scattering into these two groups of modes. For a point defect at the surface, scattering varies as the fifth power of frequency, and scattering into other Rayleigh waves is the dominant process. For point defects distributed through the volume of the solid, scattering varies as the fourth power of frequency. Expressions are also given for a line of defects normal to the surface and of finite length. For an infinite line, scattering varies as the cube of the frequency. Horizontal line defects and vertical sheets of defects have been treated in the doctoral dissertation of one of the authors (R.G.S.). These results are summarized.

ISSN:0021-8979    

DOI:10.1063/1.1662964

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A simple method for measuring phase velocities of vibration modes in a bar is described. Experimental results for aluminum are compared with values computed from theoretical curves of the phase velocity versus frequency thickness product.

ISSN:0021-8979    

DOI:10.1063/1.1662975

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The method of forming thin oxide layers by sputter etching in a low‐power rf oxygen discharge (rf oxidation) was investigated. Use of the method for oxide formation on Pb films was studied usingin situellipsometry. A steady‐state oxide thickness was observed that depended on the oxidation and sputtering parameters. For oxygen pressures of (5–40) × 10−3Torr and cathode voltages of 175–450 V, the steady‐state oxide thickness was in the 60–90‐Å range. The oxide layers grown in the rf oxygen discharge had the orthorhombic form of PbO similar to that formed by thermal oxidation. However, the PbO layers were found to be nonstoichiometric due to excess oxygen; ellipsometric measurements indicated values of 2.6–2.8 and about 0.1, respectively, for their index of refraction and extinction coefficient.

ISSN:0021-8979    

DOI:10.1063/1.1662979

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A new experimental technique has been used to measure the stopping power of CdS for He ions. This technique consists of measuring the energy spectrum of either He ions backscattered from implanted Bi or of &agr; particles emitted by an implanted radioactive isotope, such as Po210. A thin layer is then etched off the surface of the sample and the energy spectrum is measured again. The stopping power is calculated from these two spectra and the known thickness of the removed layer. These measurements and calculations have been made for energies ranging from 0.963 to 5.3 MeV with accuracies between 12% and 16%.

ISSN:0021-8979    

DOI:10.1063/1.1662990

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Neutron small‐angle scattering has been used to measure the distribution of voids in irradiated aluminum crystals. The scattering measurements were obtained with a spectrometer utilizing the focusing properties of nearly perfect germanium crystals. Direct inversion of the scattering data yields void distributions very close to those obtained with electron microscopes for similar aluminum samples.

ISSN:0021-8979    

DOI:10.1063/1.1662998

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The electron affinities of SrSe, SrTe, CaSe, and CaTe have been determined using measurements of the temperature dependences of the electrical conductivity and the thermionic emission. The values obtained were 1.77, 2.40, 2.32, and 3.53 eV, respectively. Using these values together with previously obtained values for BaO, BaS, BaSe, BaTe, and CaO and a correlation with the lattice spacings, estimates of the electron affinities of SrO, SrS, CaS, MgO, MgS, and MgSe were obtained by extrapolation.

ISSN:0021-8979    

DOI:10.1063/1.1663005

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We have studied the changes in chemical composition, capture and release of argon, electrical conductivity, and morphology of crystallization which result from changes in dc bias applied to the substrate during the rf sputtering of amorphous thin films of nominally stoichiometric GeTe2. We find (i) a strong increase of Te deficiency with negative bias, (ii) a strong increase in incorporated argon content with negative bias, (iii) a strong correlation between Te deficiency and argon content, (iv) no dependence of argon content on film thickness, (v) violent release of argon under certain circumstances, (vi) scant correlation between argon content and electrical properties, (vii) slightly stronger correlation between compositional variation and electrical properties, (viii) a residuum of unexplained variation in electrical properties, and (ix) morphological variations consistent with departures from stoichiometry. We conclude that the rare‐gas content of nonreactively sputtered chalcogenide alloys is largely inactive except insofar as it determines the kinetics of its own release at elevated temperatures, but that control of substrate potential during deposition is nevertheless essential for the attainment of quantitatively reproducible transport properties.

ISSN:0021-8979    

DOI:10.1063/1.1663015

出版商:AIP    

年代:1974

数据来源: AIP