摘要:

Lattice mismatch effects are obscured by the standard envelope wave‐function approach to electronic states because the lattice potential does not appear. A theoretical analysis of the first‐order effect of lattice mismatch is presented using the deformable ion approximation. It is found that a potential barrier of height &Dgr;, normally associated with a band offset, acquires an additional energy (E) dependent term becoming &Dgr;+&eegr;(&Dgr;−E) where &eegr; is the fractional lattice mismatch in the growth direction. For strained layers, &Dgr; includes the effect of deformation in the strained layer. Quantitatively, the lattice mismatch effect can be comparable to or larger than the deformation potential effect on the band offset. A scattering approach is employed.

ISSN:0021-8979    

DOI:10.1063/1.337780

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The effects of the Si/(Si+C) ratio in the reaction gas stream on the growth and properties of monocrystalline &bgr;‐SiC films grown on Si(100) substrates via chemical vapor deposition have been theoretically and experimentally studied. The amounts of condensed phases of &bgr;‐SiC and Si, and the partial pressures of the remaining Si and C‐containing gases as a function of the Si/(Si+C) ratio in the source gases have been initially obtained from thermodynamic calculations using the ‘‘solgasmix‐pv’’ computer program. Complementary and comparative experimental growth studies have shown that inclusion‐free films having maximum values in growth rate and carrier concentration and a minimum value of resistivity were obtained near Si/(Si+C)=0.5.

ISSN:0021-8979    

DOI:10.1063/1.337075

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

This paper deals with the injection of minority carriers, through a contact or junction, into materials of high resistivity and low carrier lifetime. Semi‐insulating III‐V compounds and many amorphous materials come under this heading. Since the macroscopic transport equations cannot be analytically solved, it is necessary to resort to numerical computation. Recent work along those lines has shown that the nature of the assumed boundary conditions has a profound effect on the results. The relationships are illustrated by concentration and potential contours of semi‐infinite andp‐i‐nsystems, with various ratios of lifetime to dielectric relaxation time.

ISSN:0021-8979    

DOI:10.1063/1.337076

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The apparatus is described that has been used to determine the lifetime, the effective recombination velocity, and the diffusion length near the grain boundary in a polycrystalline silicon solar cell. The lifetime has been estimated from rise of the electron‐beam‐induced current after switching on the incident electron beam; the diffusion length and the effective recombination velocity have been determined from the steady‐state electron‐beam‐induced current characteristics. The experimental rise‐time characteristics are compared with theoretical ones.

ISSN:0021-8979    

DOI:10.1063/1.337077

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Using an rf‐magnetron sputtering method, highlyc‐axis‐oriented La‐modified PbTiO3(PLT) thin films with compositions of Pb1−xLaxTi1−x/4O3, wherex=0.05, 0.10, and 0.15, have been obtained on MgO single‐crystal and epitaxial Pt thin‐film substrates under conditions of low gas pressure and low deposition rate. The degree ofc‐axis orientation of the PLT films decreases, and the tetragonality of PLT becomes smaller with increasing La content. The Curie point of the films decreases at a rate of 18 °C/at. % of La with an increase of La content.D‐Ehysteresis loops were observed, and these became slim and symmetric with increasing La. It was found that significant pyroelectric currents are detected on all as‐grown specimens even without a poling treatment, and the directions are the same in all specimens. Relative dielectric constant &egr;rdecreases, and pyroelectric coefficient &ggr; increases with increasing degree ofc‐axis orientation. &egr;rand &ggr; became large with increase of La content in the films. Considering the figure of merit for pyroelectric infrared detection and the temperature coefficient of &ggr;, it was concluded that PLT films withx=0.10 were good material for pyroelectric infrared detectors.

ISSN:0021-8979    

DOI:10.1063/1.337078

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The analytical description of transient switching characteristics in Form I poly(vinylidene fluoride) has previously been confined to the narrow time range where the switching current displays a modest peak under an applied dc field. We show here that this range can be broadened to include the entire switching process by considering the process to be composed of two successive events, the first involving only the nucleation of microdomains and the second entailing the random nucleation and two‐dimensional growth. The model has been successfully applied to data obtained at temperatures between 20 and −80 °C from a sample that had been either unirradiated or irradiated with &ggr; rays (10 Mrad). Furthermore, our analysis revealed that the irradiation, which enhances the retention characteristics of piezoelectric property at elevated temperatures, primarily affects the main switching process by suppressing the rate of nucleation.

ISSN:0021-8979    

DOI:10.1063/1.337079

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A previously developed model for the angular dispersion of Raman scattering power from the surface of absorbing centrosymmetric cubic materials is extended to absorbing materials of the zinc blende type. Independent expressions have been obtained which give the scattered power due to the longitudinal and transverse long‐wavelength optical phonons as a function of external scattering geometry parameters; from these calculations, it has been found that the ratio of the scattered powers shows significant dependence on the angles of incidence and detection. These results provide a quantitative method in assessing the effects of choosing an approximate rather than the exact backward scattering geometry. Experimental results obtained from GaAs are in very good agreement with the predictions of the model. Examples of physical situations are given where angular dispersion corrections become necessary.

ISSN:0021-8979    

DOI:10.1063/1.337080

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Erasability in an overcoated organic dye‐binder medium has been demonstrated. With thin (∼50 nm) overcoats on such media, a laser pulse forms a pit in the dye‐binder layer, while the overcoat forms a dome over the pit. Information is erased by heating the rim material with low laser power which fills the recorded pit. During recording into a thickly (∼300 nm) overcoated recording medium, material flow occurs from the trailing edge towards the leading edge of the mark. Results of modeling, observations of pit morphology, evidence of long‐term stability, and measurements of optical disk performance are presented for thinly and thickly overcoated erasable organic dye‐binder layers.

ISSN:0021-8979    

DOI:10.1063/1.337081

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Mark formation by laser writing in an overcoated thin‐film tellurium alloy‐based optical storage media with a trilayer design was studied by transmission electron microscopy, scanning electron microscopy, optical microscopy, differential interference contrast optical microscopy, and optical interferometry. Mark formation was observed to occur through coalescence of the relatively uniform amorphous tellurium alloy film into discrete particles. The mark microstructure and, correspondingly, the optical properties of the mark, were dependent on the write laser power. At low power, incomplete breakup of the film occurred. At high power, the film coalesced into spherical particles. Laser writing also caused changes in the organic overcoat layer.

ISSN:0021-8979    

DOI:10.1063/1.337082

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The absorption and scattering (reflection plus transmission) energy spectra of normally incident 24.8‐MeV electrons on C, Al, Cu, and Pb foils have been calculated using an updated version of the relativistic Monte Carlo electron/photon transport codesandyl. The theoretical results are compared with recent experimental data and good agreement is found.

ISSN:0021-8979    

DOI:10.1063/1.337083

出版商:AIP    

年代:1986

数据来源: AIP