摘要:

The subtle structure‐property relationship in magnetic multilayers is addressed by an array of techniques. Fe/Pt multilayers prepared by magnetron sputter deposition are characterized using x‐ray diffraction, Auger depth profiling, electron microscopy, magnetometry, and x‐ray magnetic circular dichroism. We concentrate on the (Fe9/Pt9)92which is [111] textured in the growth direction, but randomly oriented in‐plane, with average grain size of 30 nm. This sample is magnetized in‐plane, as determined by magnetometry as well as magnetic circular dichroism (MCD). The potential of MCD to follow the magnetic axis orientation in these samples as well as provide an element specific determination of the magnetic moment will be discussed.

ISSN:0021-8979    

DOI:10.1063/1.355055

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

An H2dissociation model in the diamond deposition process is described and discussed using the results of a Monte Carlo computer simulation. A hot filament assisted chemical vapor deposition technique with substrate bias voltage was assumed and electron trajectories were computed. In this model, molecular hydrogen is dissociated by the impact of electrons accelerated towards the substrate. The number of dissociative collisions occurring while one electron flies from the hot filament to the substrate was calculated varying both the bias voltage and the gas pressure. The results we obtained here suggest that (1) the number of dissociations increases toward the biased substrate; (2) the production of H atoms generated in the gas phase is a function of the ratio of electric field to gas pressure,E/p; and (3) there is an optimum condition ofE/prequired to obtain efficient dissociation.

ISSN:0021-8979    

DOI:10.1063/1.355056

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

This communication presents a comparison of three values of third‐order nonlinear permittivity of &agr;‐quartz that have been obtained independently by three different methods. Each method produces a value of a different order of magnitude, in the range between 10−22and 10−20F/m, and with no uniformity in sign among them. This apparently represents the most pronounced conflict existing today among third‐order nonlinear electromechanical constants of quartz obtained from various sources. No explanation for the conflict is readily available.

ISSN:0021-8979    

DOI:10.1063/1.355057

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The local symmetry of dislocation centers in CdS crystals was studied by piezospectroscopy of space resolved photoluminescence of individual screw dislocations. The limited set of dislocationCscenters (2 from a total of 6) was found to be characteristic for each screw dislocation and that set determines the asymmetry of the core structure. The space‐ and time‐nonstationarity of the dislocation domains observed in the polarized emission of dislocations are explained by the reorientation of one‐dimensionally orderedCscenters in the core of the screw dislocation gliding by the Peierls mechanism.

ISSN:0021-8979    

DOI:10.1063/1.355058

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Optoelectronic modulation spectroscopy has been applied to field effect transistors. Spectra include responses from bulk levels as well as from the continuum of states at the insulator‐semiconductor interface. States that are energetically deep in a continuum can be probed but would not be accessible to the Fermi level in an electrical measurement.

ISSN:0021-8979    

DOI:10.1063/1.355059

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

MBe2BO3F2(M=Na,K) have been discovered to be nonlinear optical (NLO) materials for UV applications. They have relatively large NLO coefficients:deffis about 2.5 times as large as that of KH2PO4(&lgr;=1079 nm, Nd:YAP laser), the UV cutoff wavelengths are as short as 155 nm, and they have a moderate birefringence of nearly 0.10. Their structures are characterized by an infinite sheet which is formed by six‐membered rings [Be2BO6F2] with Be‐O and B‐O edges in common. Such structures are favorable for good NLO properties. These NLO properties make MBe2BO3F2promising candidates for vacuum UV NLO materials.

ISSN:0021-8979    

DOI:10.1063/1.355060

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The effects of substrate temperature on the deep trap property of In0.52Al0.48As layers grown by molecular beam epitaxy lattice matched on InP substrates have been investigated. Deep level transient spectroscopy measurements have been used to characterize the InAlAs layers and analyze the effects of growth kinetics on the deep traps in the epitaxial layers. Two new deep traps have been found in the samples grown at relatively low growth temperatures, which do not show in the samples grown above 450 °C. The activation energies of these traps are obtained as &Dgr;ET=0.45±0.03 and 0.62±0.02 eV for EI1 and EI2, respectively. A measurable decrease in the densities of EI1 and EI2 was detected following the heat treatment at temperatures above 500 °C.

ISSN:0021-8979    

DOI:10.1063/1.355061

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Direct preparation of high coercivity gamma iron oxide (&ggr;‐Fe2O3) thin films by chemical vapor pyrolysis techniques have been described. Films deposited at temperatures above 500 °C have the &ggr;‐ and those deposited below 500 °C have the &agr;‐Fe2O3phase. Gas phase reactions leading to oxygen deficiency in the vicinity of substrate and consequently controlledinsituoxidation of Fe3O4appear responsible for direct growth of the &ggr;‐Fe2O3film. Magnetic properties of these films are optimized by adding cobalt. High coercivity values of 3 kOe for directly deposited &ggr;‐Fe2O3films containing 6 at. % of cobalt are obtained along with reasonable values of remanence ≊2.8 kG and squareness ratio of 0.83. These values are considerably superior for magnetic recording in comparison to those for &ggr;‐Fe2O3films obtained by reduction and reoxidation of &agr;‐Fe2O3films.

ISSN:0021-8979    

DOI:10.1063/1.355062

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We demonstrate that GaAs grown by molecular beam epitaxy on silicon has ideal characteristics for THz receiver applications. The lattice mismatch between silicon and GaAs causes a disordered growth of GaAs, reducing the carrier lifetime to 1.8 ps. This is similar to the characteristics observed in low temperature grown GaAs. Furthermore, the high resistivity silicon substrate has a very low absorption and dispersion in the far infrared. This makes it an ideal material in THz system applications, and we show that a maximum frequency of 5 THz and a sixfold increase in sensitivity can be obtained using a GaAs‐on‐silicon based THz detector.

ISSN:0021-8979    

DOI:10.1063/1.355040

出版商:AIP    

年代:1993

数据来源: AIP