摘要:

The piezoresistive gage factor of boron‐doped CVD polysilicon films deposited with a boron‐to‐silicon ratio of 2×10−4–1.2 ×10−2on an aluminum‐oxide‐insulated molybdenum substrate is found to be between 15 and 27. Annealing increases the gage factor. The higher the doping, the lower is the gage factor. Over the range 20–140 °C, the gage factor is not temperature sensitive if the boron‐to‐silicon ratio is higher than 2×10−3during deposition. The temperature dependence increases as the doping concentration is decreased. Our analysis shows that the piezoresistive properties in polysilicon is mainly due to the bulk crystallites.

ISSN:0021-8979    

DOI:10.1063/1.322515

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Measurements of the temperature dependence of the dielectric constant and polarization in a constant field have been made on nominally pure SrTiO3ceramics and SrTiO3ceramics containing vanadium and niobium impurities. The peaks in the dielectric constant and the remanent polarization observed are apparently not due to a ferroelectric or antiferroelectric transition but rather to the presence of a thermoelectret state existing for permanent dipoles in the materials. It is suggested that the permanent dipoles have an origin similar to the impurity‐vacancy dipoles found in alkali halides.

ISSN:0021-8979    

DOI:10.1063/1.322516

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The polarization of a KTaO3single crystal and some KTaO3ceramic specimens has been measured using a dc technique. A remanent polarization was found as well as hysteresis in the polarization as a function of field. Peaks in the ac dielectric constant were also observed. These dielectric properties are attributed to dielectric relaxation effects and the existence of an electret state.

ISSN:0021-8979    

DOI:10.1063/1.322517

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We have used x‐ray photoelectron spectroscopy to determine the valence of diffused titanium in LiNbO3. Our measurements show Ti ions only in the +4 valence state within the sensitivity of the measurement technique. Further analysis of our data indicates that the Ti ions occupy a unique site in the LiNbO3unit cell.

ISSN:0021-8979    

DOI:10.1063/1.322518

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Corona‐charged polypropylene‐film electrets are reported to give a reversible short‐circuit electrical current when subjected to a change in temperature. This current varies as the time derivative of the temperature; we point out a linear dependence of the signal amplitude on the charge of the electret. We show that without specific assumptions concerning charge trapping, the sample expansion cannot account for this pyroelectric behavior. The results can be explained in terms of either a dipolar distribution or a noncentrosymmetry of the trapping centers.

ISSN:0021-8979    

DOI:10.1063/1.322519

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We report on high‐energy transfer between two surface acoustic waves propagating on CdS and Bi12GeO20crystals separated by an air gap. We use first a simple one‐dimensional model and second a perturbation approach to show that under special conditions a strong coupling can occur. We have performed experiments using Rayleigh modes, and found minimum transfer losses of 7 dB at 25 MHz and 13 dB at 65 MHz with an air gap of a few thousand angstroms.

ISSN:0021-8979    

DOI:10.1063/1.322520

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A method is discussed for measuring the separate spatial distributions of fixed charge and permanent polarization in a uniform insulator. Changes in the potential difference across the insulator are measured when a known nonuniform time‐dependent temperature perturbation is established through the sample thickness. The contributions to the measured signal from real charge and polarization charge have the same form, but are weighted differently. Deconvolution of the experimental data, therefore, yields a linear combination of the spatial distributions of real and polarization charges. These two distributions can be separated by utilizing the temperature dependence of these weighting factors.

ISSN:0021-8979    

DOI:10.1063/1.322521

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Point defects, introduced at 4.2 °K inp‐type silicon by 1.5‐MeV electron irradiation, are studied by means of the thermally stimulated capacitance technique. Electronic states associated with the vacancy and the divacancy are observed, which enables us to study their correlated annealing. The respective donor energy levels, hole thermal emission rates, and annihilation activation energies are measured.

ISSN:0021-8979    

DOI:10.1063/1.322522

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Computational models of dynamic ductile and brittle fracture are developed for wave propagation in one‐ and two‐dimensional geometries. The model features have been taken mainly from detailed observations of samples partially fractured during impacts, but the functional forms are consistent with theoretical results where applicable. Basic features of the models are the nucleation and growth (hence, the acronym NAG for the models) of voids or cracks, and the stress relaxation resulting from the growing damage. The results of the calculations include number and sizes of cracks, voids, or fragments as a function of position in the material. The NAG analysis presents the nucleation law, determined from experiment, and two growth laws: both growth and nucleation are functions of stress and stress duration. Procedures for treating cracks with a range of sizes and orientation are presented with the method for computing the stress relaxation that accompanies growth of damage. Brittle fracture is essentially anisotropic in actuality and in the model: cracks nucleate and grow as a function of stress normal to their plane, and the stress relaxation is a function of crack opening in the direction of the stress. Criteria are presented for the coalescence of cracks to form fragments and for complete fragmentation. The computational models have been applied to one‐ and two‐dimensional wave propagation problems. The NAG models have been shown to be applicable to several metals, a plastic, and a quartzite, to stress levels from just above threshold to ten times the threshold, and to load durations from 20 nsec to several microseconds. The damage has been computed for stress waves caused by impact, thermal radiation, and explosion.

ISSN:0021-8979    

DOI:10.1063/1.322523

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The stability of electric arc discharges has been explored through the use of an energy balance coupled with charge conservation. In order to facilitate this analysis, a new model for the electrical conductivity function has been proposed. Asymptotic solutions for the arc governing equations have been obtained. Stability criteria have been developed from both the linear theory (infinitesimal size disturbance) and from a minimizing solution point of view for finite size disturbances. The results delineate an open region in the stability diagram where arc instabilities may be possible.

ISSN:0021-8979    

DOI:10.1063/1.322524

出版商:AIP    

年代:1976

数据来源: AIP