摘要:

The peak frequency, width, and shape of the transverse-optical (TO) and longitudinal-optical (LO) infrared absorption modes of silicon oxides (SiO2, SiOx), silicon nitrides (Si3N4, SiNx), silicon oxynitrides (SiOxNy), and other silicon compounds have often been connected with stress, stoichiometry, defects, structural order, and other properties of the layers. However, certain geometrical effects strongly influence the spectral response of the material independent of its physical or structural properties. The influence of layer thickness, multilayer configuration, substrate effects, angles, and polarization on the behavior of TO and LO bands are presented and discussed. Some corrections are suggested to reduce experimental error and for the reliable measurement of stress, composition, disorder, and structure. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364049

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This paper describes a study of the effect of an external electric field on the behavior of positrons in metal-oxide-silicon (MOS) systems. Doppler broadening measurements of the annihilation radiation were performed on capacitors with identical thermally grown SiO2layers and with Al, W and Au layers as a gate. The data were analyzed by the combined use of the shape- and wing-parameters of the photo peak. The observed effects of the electric field are due to the field-driven transport of positrons through the SiO2,silicon and the interfaces. By applying a field of the order of 1 MV/cm the positrons can be efficiently transported through the approximately 100 nm thick SiO2layer. From the transport behavior of the positrons it is concluded that the positron affinity is higher for SiO2than for silicon and for the gate metal. By properly choosing the direction of the field, the positrons implanted into the SiO2layer are collected either at the Si/SiO2interface or at the SiO2/gate interface. For negative gate bias the positrons implanted into the substrate, that diffuse back to the SiO2,are transported through the oxide layer and injected into the gate metal. This is the first time that field-assisted transport of positrons across an insulating layer has been demonstrated. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364050

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this article the magneto-optics of magneto-optical (M-O) layered structures have been studied theoretically and experimentally. For the air/M-O/air configuration, an analytic expression between the apparent complex Faraday rotation and the eigenvalue&fgr;˜F=e1&fgr;˜F′can be obtained, when the M-O layers are semitransparent and weakly magnetic. The interference factore1is a function of the optical constants and the M-O layer thicknessd, and the light wavelength. In these structures, the apparent Faraday rotation consists of two parts. One oscillates as a function of the M-O layer thickness and the other is proportional to the layer thickness. The oscillation period and the amplitude are determined by the optical constants of the M-O layers. For the air/M-O/reflector configuration, the Kerr rotation&fgr;˜koscillates as a function of the M-O layer thickness and approaches a constant as the thicknessd→∞. If the M-O layers are semitransparent and weakly magnetic, the apparent Kerr rotation can be expressed as&fgr;˜k=e2&fgr;˜F′.For ultrathin metallic magnetic bilayered films the Kerr rotation is proportional to the M-O layer thickness and the enhancement factor is a function of the optical constants of the M-O layer and NM reflector. The magneto-optics of a Co spinel ferrite film, Co/Cu, Fe-Ni/Cu, and Co/Si structures have been studied experimentally. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364051

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have proposed a new type of reverse-mode polymer-liquid crystal device: homeotropic reverse-mode polymer-liquid crystal (HRPLC). This device consists of a liquid crystal with a dielectric constant having negative anisotropy and a pair of glass plates covered with a homeotropic alignment layer. The HRPLC’s operation is the reverse of the usual; i.e., it is clear when no voltage is applied and opaque under applied voltage. We have confirmed that the HRPLC operates well in reverse mode and have studied the dependence of its properties on liquid crystal material, curing process, and cell thickness. Experimental results indicate the HRPLC has a 30:1 contrast ratio over an operating voltage range of 0–11 V. In special fabrication conditions, the transmittance–voltage curve of the HRPLC drops to a minimum at a certain voltage level and begins to increase at that point. We have proposed a model to explain this result. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364052

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A theoretical study of the nucleation, size, and structure of diamond phase carbon clusters on Si(111) substrates is presented. Molecular mechanics analysis has been utilized to predict energetically and entropically feasible pathways for nucleation of the carbon clusters. Several mechanistic pathways for nucleation of carbon clusters are examined with CH3and/orC2H2as the nucleation precursors. A possible model for the nucleation mechanism of diamond-phase carbon clusters on the &bgr;-SiC(111) surface, which forms epitaxially on Si(111) substrates, is presented. The critical size of the carbon clusters is computed based on the atomistic theory of nucleation and the proposed nucleation mechanisms. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364053

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We used x-ray photoelectron spectroscopy to investigate the chemistry of O impurity atoms in CdS thin films grown for photovoltaic purposes by chemical-bath deposition (CBD). We compared the Cd3dphotoline, O1sphotoline, Cd MNN Auger line, and O KLL Auger line taken from a CBD CdS thin film, CdS single-crystal reference, Cd metal reference, CdO reference, and Cd(OH)2reference. This comparison showed that the O present in thin-film CBD CdS is a manifestation of H2O incorporated into the film during the CBD growth. Ar+ion sputtering, a technique frequently used in thin-film analyses, preferentially removed S from the CBD CdS thin film and created CdS1−xOx(x∼0.04) in the surface region from the incorporated O impurity. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364054

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An integral equation method is used to calculate particle–particle forces in electrorheological fluids. The method focuses on the gap region between particles where large electric-field concentrations occur. Effects due to time-dependent excitation and nonlinear (field-dependent) fluid conductivity are analyzed. It is found that the response to step-function changes in applied field closely follows a simple form that can be derived from the dipole approximation. Qualitatively different stress-vs-time curves are obtained for large dielectric mismatch (e.g., barium titanate/dodecane) relative to large conductivity mismatch (zeolite/silicone oil). In fluids where the conductivity is strongly field dependent, it is found that particle–particle forces scale linearly with applied fieldE0at large fields. Likewise, the shear yield stress scales asE03/2.©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364231

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this article, a new charge-extraction algorithm is proposed for extracting the spatial distributions of hot-carrier-induced interface states and trapped charges inp- andn- metal-oxide-semiconductor field-effect transistors, based on the charge-pumping measurement data. This extraction algorithm is physics based and provides a better understanding of how the presence of hot-carrier-induced trapped charges and interface states affect the charge-pumping curves. The extraction time for this new algorithm is very fast (typically 30 s) and does not require very tedious computer simulation. The verification of this method was performed using TSUPREM-4 and MEDICI simulations. With this new extraction method, one can gain better insight into the degradation mechanisms taking place under different hot-carrier stressing conditions. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364055

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The penetration depth and surface resistance of a superconductor depend upon the superfluid current density. This dependence gives rise to nonlinear mixing in a superconducting microstrip resonator. Here we discuss the problem of intermodulation in which two signals at&ohgr;1and&ohgr;2, laying within the pass band of a microstrip cavity resonance, mix and generate a signal at2&ohgr;1−&ohgr;2. An expression relating the power generated at2&ohgr;1−&ohgr;2to the power transmitted at&ohgr;1and&ohgr;2is given. We focus on the high-Tcsuperconductors where it is believed that the order parameter hasdx2−y2symmetry. We find for a resonator with a large unloadedQthat intermodulation arises dominantly from the reactive nonlinear inductance of the superconducting film. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364056

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Partly resistive superconducting quantum interference devices (RSQUIDs) are used in noise thermometry in the liquid helium temperature range. Here we analyze one type of RSQUID that has not been thoroughly investigated until now: the direct current biased with two Josephson junctions and a resistive part connected in series with the junctions and closed by a superconducting ring. The resistive shunted model of the Josephson junctions is used for the analysis. Two cases of the RSQUID ring inductance were analyzed: (i) negligibly small and (ii) small but finite inductance. The expressions for the low frequency output signal, the current–voltage(I–V)characteristics, and the current flowing through the resistive part are obtained. In the dependence of the output frequency versus the dc current passed through the resistive part often an offset is observed experimentally. This phenomenon can be explained as an influence of an asymmetry in the critical currents of the junctions. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364057

出版商:AIP    

年代:1997

数据来源: AIP