摘要:

A Sputtering apparatus was equipped with an optical spectrometer by which both the fluorescence from the glow discharge and the luminescence from the growing film could be detected and measured separately. Calcium, magnesium, and lanthanum oxide layers doped with samarium or terbium were used as targets. It was observed that the luminescence appeared when calcium or magnesium oxides were used as host materials, but was absent in the case of lanthanum oxide. The thickness of the layer in which the excitation took place was found to be a few hundred angstroms. The possible reason for the weaker luminescence efficiency of lanthanum oxide in comparison with calcium and magnesium oxides has been discussed.

ISSN:0021-8979    

DOI:10.1063/1.1662855

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

In this paper a study of surface charge decay has been made on polyethylene terephthalate thermoelectrets prepared from foils of thicknesses 6, 25, 75,and 250 &mgr; under various conditions of polarization. Initially, heterocharges have been observed on both the surfaces, while final charges one month after preparation were homo‐ on the cathode surface and hetero‐ on the anode surface. Infrared absorption characteristics have also been studied. Experimental evidence is given for dipolar alignment during polarization in this polymer. Dipole alignment and space charge trapping are shown to be the main causes of electret polarization in polyethylene terephthalate. Relaxations of dipoles and trap hopping processes are responsible for the charge decay.

ISSN:0021-8979    

DOI:10.1063/1.1662856

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The well‐known Morse function &phgr;(r) =D{exp [−2&agr;(r−r0)] −2 exp [−&agr;(r−r0)]} can be considered to be a particular case of the general family of potential functions with exponential attraction and exponential repulsion, viz., &phgr;m(r) = [D/(m−1)] {exp[−m&agr;(r−r0)] −m× exp[−&agr;(r−r0)]}. This study examines the suitability of applying the functions &phgr;m(r) to the description of mechanical properties of cubic crystals. For bcc lattices, the ratioC11/C12for the theoretical model of the crystal made up of atoms with &phgr;m(r) interatomic interactions is shown to be too small to provide a realistic description of bcc metals; also, the bcc crystals are found to be inherently unstable for larger values of &agr;a0, wherea0is the lattice parameter of the crystal. For fcc lattices, however, the theoretical model of the crystal is found to be mechanically stable for arbitrary (i.e.,m>1) exponentially attractive and repulsive interactions and the elastic moduliC11andC12of the theoretical fcc crystals are found to be capable of conforming to the respective experimental values of fcc metals. The results are in agreement with Born's analyses of lattice stability. Numerical values ofD, &agr;, andr0are calculated for several different values of the parametermfor fcc Ni using experimental values ofC11,C12, and lattice parameter. The element Ni is selected because, among the fcc metals, Ni most closely obeys the Cauchy conditionC12=C44. The functions &phgr;mare then used to calculate theoretical pressure versus volume (P‐V) behavior (at pressures large enough to produce considerable anharmonicity) and the results are compared with experiment; good agreement is found between the calculated and experimentalP‐Vrelations.

ISSN:0021-8979    

DOI:10.1063/1.1662857

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Numerical calculations are made of the theoretical strength of fcc crystals with two‐body exponentially attractive and exponentially repulsive interatomic interactions; the crystals are subjected to unconstrained (100) uniaxial tension and compression. The calculations are made from the point of view of mechanical lattice stability; the general theory has been presented in an earlier paper. The numerical values of the parameters characterizing the interatomic interactions were calculated from the elastic moduliC11andC12and the stress‐free equilibrium value of lattice parameter for Ni; the element Ni was selected for this purpose because (i) the Cauchy condition is not severely violated for Ni, (ii) the correct (i.e., experimental) linear elastic stress‐strain behavior is exhibited by the theoretical model of the crystal, and (iii) reasonably good agreement is obtained between theoretically calculated and experimentally observed anharmonic pressure‐vs‐volume behavior. Calculations are carried out using relatively short‐range steep and long‐range shallow atomic potential functions; remarkably good agreement is found among results of calculations made wth the different atomic potentials. The theoretical strength and corresponding strain in tension is about 1.6 × 1011dyn/cm2and 10.5%, respectively. The modes of lattice failure are examined. Under sufficient compression, the lattice slips into a stress‐free bcc structure which appears at a local energy maximum; the bcc structure is mechanically unstable.

ISSN:0021-8979    

DOI:10.1063/1.1662858

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The characteristics of electroacoustic surface waves supported by a curved piezoelectric‐vacuum boundary are studied. A coaxial structure with a piezoelectric insulator as the inner cylinder and an electric conductor as the outer cylinder is considered. A dispersion relation for electroacoustic surface waves circulating around the periphery of the piezoelectric cylinder is obtained. Asymptotic solutions are compared with numerical solutions. Profiles for the mechanical displacement and electric potential for various modes are presented. Possible application as delay lines with long‐time delay is indicated.

ISSN:0021-8979    

DOI:10.1063/1.1662859

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Ideal growth parameters for obtaining large transparent crystals of NH4Cl and NH4Br by vapor‐phase technique are described. The electrical conductivity of such cystals and crystals grown from solution are reported. In pure NH4Cl crystals two regions with slopes 1.26 and 0.8 eV are obtained in the log&sgr;Tvs 1/Tplot. In impurity‐doped NH4Cl crystals a third region with slope 1.04 eV is also observed. In pure NH4Br crystals two regions with slopes 1.06 and 0.66 eV are obtained.

ISSN:0021-8979    

DOI:10.1063/1.1662860

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

We have investigated the composition and growth kinetics of hafnium silicides (HfSi and HfSi2) formed from thin films of hafnium sputter deposited on silicon. Backscattering of MeV He ions was used to monitor the growth of the silicide phases and to determine the Si/Hf concentration ratios. Seemann‐Bohlin x‐ray diffraction techniques provided identification of the phases and an estimate of the crystallite size of the films. The stable‐phase HfSi forms in the temperature region 550–650 °C. The reaction initiates at the Hf/Si interface and the thickness of the HfSi increases proportional to the square root of time. The HfSi grows by diffusion of Si through the already formed phase with an interdiffusion constantD≃ 2.4 exp(−EA/k T) cm2/sec withEA= 2.5 eV. Different behavior is observed for the formation of the HfSi2. In this case the silicide forms simultaneously throughout the HfSi layer at temperatures above 750 °C. We propose that the HfSi2nucleates at the grain boundaries of the HfSi, rather than at the Si/HfSi interface. The transition to HfSi2is completed rapidly because of the large density of nucleation sites and the small grain size of the film.

ISSN:0021-8979    

DOI:10.1063/1.1662861

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Cadmium sulfide implanted with bismuth at room temperature has been investigated. The sputtering efficiency was measured and related to the saturated bismuth concentration in the implanted layer. Etching experiments were performed to determine the role of the high surface concentration of the implanted bismuth and the visibly discolored damage region that results from the implantation. Diodes were fabricated and their forward‐biased characteristic studied. It was found that thep‐type behavior of the implanted layer was not confined to the visibly damaged surface layer. A critical minimum dose was necessary to observep‐type behavior.

ISSN:0021-8979    

DOI:10.1063/1.1662862

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The elastic constants of single crystals of double hcp allotrope of praseodymium have been measured over the temperature range 4.2–300 K. Maxima are observed near 100 K in the temperature dependences ofC11,C33, and (C11−C12)/2, and minima are observed near 30 K. The maxima correlate with the upper temperature limit of an anomalous contribution which has been reported in the heat capacity. The minima correlate with peculiar behavior which has been observed in other physical phenomena. Inference may be drawn from the elasticity data that the thermal expansion behavior of praseodymium at low temperatures is very highly anisotropic. Comparison of the elastic constants of praseodymium with available data for the other rare earths shows that the praseodymium data fit a general pattern. Evaluation from the elastic constants shows that the Debye temperature of praseodymium remains nearly constant throughout the temperature range of measurement within ± 2 K of 152 K.

ISSN:0021-8979    

DOI:10.1063/1.1662863

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Thin films of ZnO with a large degree of preferred parallel orientation have been rf bias sputtered onto sputtered indium‐tin oxide (ITO) on quartz. The orienting effect of the ITO film is partly due to some limited chemical reaction at the ZnO/ITO interface and partly due to a surface microtexture. An x‐ray pole figure analysis indicates that the (10.0) planes of the ZnO are parallel to the substrate surface within ± 5° and that the direction of thecaxes is parallel to the target surface within ± 20°. The preferred orientation of thecaxes is only observed if both the ITO and the ZnO are sputtered onto the substrate at the same oblique incidence. The ZnO films have resistivities of the order of 108to 1010&OHgr; cm. If the ITO/ZnO film couple is deposited onto a well‐conducting ground electrode, efficient shear‐wave transducers can be obtained.

ISSN:0021-8979    

DOI:10.1063/1.1662864

出版商:AIP    

年代:1973

数据来源: AIP