摘要:

Solid solutions of BiFeO3and PbZrO3were investigated for crystallographic and dielectric properties. A new pseudocubic perovskite phase was found, which has been tentatively indexed as orthorhombic with the same unit cell as PbZrO3but with dielectric properties characteristic of a ferroelectric substance. The Curie point in this series of solid solutions has a minimum of about 155°C at a composition of about (PbZrO3)0.80(BiFeO3)0.20, which at room temperature lies on the boundary between the orthorhombic antiferroelectric and the pseudocubic ferroelectric phases. This composition has a relative dielectric constant of 800 at room temperature and shows appreciable dielectric nonlinearity. The Curie point rises to about 400°C for (PbZrO3)0.50(BiFeO3)0.50and is extrapolated to about 900°C for pure BiFeO3, in agreement with previous data from similar solid solutions. It is felt that this is additional evidence that the distortion from cubic symmetry in BiFeO3may be of ferroelectric origin.

ISSN:0021-8979    

DOI:10.1063/1.1709009

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An emission line in GaP of previously unexplained origin peaking at about 1.96 eV (6300 Å) at 77°K was studied in electroluminescence of forward biasedp‐njunctions and in photoluminescence. We attribute this band to the presence of Si. The peak energy position of the 1.96‐eV band is dependent on the identity of the dominant shallow donors, thereby indicating that the deep center is an acceptor. The results indicate that Si substitutes at Ga sites and acts as a shallow donor. At high‐electron concentrations, Si causes the appearance of an acceptor with a level about 0.25 eV above the valence band. The dependence of current and light intensity on voltage was studied. The 1.96‐eV line has an external quantum efficiency at 77°K of up to 1.4×10−2but is rapidly quenched with increasing temperature.

ISSN:0021-8979    

DOI:10.1063/1.1709011

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An arc discharge of 60‐&mgr;sec duration and peak current of 2×104A in an initial pressure of 3 Torr of helium was studied spectroscopically. Time resolution was obtained by Kerr cell shuttering a 1.5‐m spectrograph. The spectra were analyzed by Stark broadening and line‐to‐line intensity ratios. The arc was found to quickly evolve many times the initial density in wall and electrode materials, to decrease in degree of excitation after the first 10 &mgr;sec, and to lack thermodynamic equilibrium. The doubly ionized species were found to have roughly consistent temperatures of 7±1.5 eV and the singly ionized species 4±1.5 eV. The ratio between the two populations was more appropriate to excitation energies of 1 or 2 eV.

ISSN:0021-8979    

DOI:10.1063/1.1709012

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Electroviscosity is defined in this introductory paper as an essentially instantaneous reversible change in apparent viscosity when a fluid is subjected to an externally applied electric field. The electroviscous properties of silica and calcium titanate dispersions are typical of most electroviscous systems and were found to be a function of many parameters such as composition, shear rate, field strength, frequency, and temperature. When only one parameter is varied, electroviscous effects increase with increasing volume fraction of disperse phase, field strength, and temperature, but decrease with increasing shear rate and frequency. Electroviscosities are proportional to the square of the field strength and inversely proportional to the first power of the shear rate. Induced interfacial polarization on and near the particle surface and the resulting interactions between the polarized double layers, and the polarized double layers and particles are used to explain the electroviscous phenomenon.

ISSN:0021-8979    

DOI:10.1063/1.1709013

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The induced interfacial polarization mechanism invoked to explain electroviscosity requires a direct relationship between the rheological and electrical properties of an electroviscous system. Static and dynamic measurements of the electric and dielectric properties of electroviscous silica dispersions were made to study these relationships. An electrokinetic potential and conductivity and a small dc power output that depend upon shear rate were observed. Electroviscous fluids under shear exhibit the characteristics of small electric cells. Shear‐induced desorption of weakly held charge carriers out of the double layer is suggested to explain these effects.On application of an external electric field, electroviscosity appears at the onset of current flow. Dielectric measurements under zero‐shear conditions show that the medium in contact with the disperse phase is essentially a low‐dielectric‐constant vehicle while the particles are composites having higher dielectric constants, thereby facilitating interfacial polarization. Anomalous dispersion occurs under zero‐shear conditions at low frequencies as expected on the basis of the proposed interfacial polarization mechanism. Simultaneous dielectric‐constant, loss, and electroviscosity measurements under shear conditions correlate with the effects of changing shear rate, field strength, temperature, and frequency. Increasing temperatures promote polarization while shear stresses transverse to the direction of the applied field perturb the field‐induced polarization. When an electroviscous dispersion is subjected to both mechanical shearing and an external electric field, a dynamic equilibrium is established between the rheological and electrical properties of the system.

ISSN:0021-8979    

DOI:10.1063/1.1709014

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Dislocations introduced into the surface layers of silicon crystals by boron and phosphorus diffusion treatments of the type used in device manufacture were studied by transmission electron microscopy. Edge dislocation arrays were found for {110} and {111} surface orientations as was the case for previous observations on {100} specimens. The maximum density of dislocations was located at a depth corresponding to the steepest solute concentration gradient. The observations suggest that the glide mechanism for motion of edge dislocations into a crystal, previously proposed for diffusion into a {100} surface, does not operate for a {111} surface orientation. Most of the edge dislocations making up the accommodation network for the latter orientation apparently had moved into the crystal nonconservatively.

ISSN:0021-8979    

DOI:10.1063/1.1709015

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The defect substructure produced by a double diffusion of boron and phosphorus into a silicon wafer has been studied by transmission electron microscopy. Specimens were examined at all stages in the diffusion and at all important levels in the finaln‐p‐ntransistor wafer for both {111}‐ and {110}‐oriented wafers. Similar specimens in the {112} orientation were examined at the emitter surface only.Diffusion‐induced dislocations and precipitates were observed at the emitter surface in all orientations. No defects were found at other levels in the doubly diffused wafers except for {110} foils in which long dislocations capable of glide on the inclined {111} planes were observed at the emitter base junction.The precipitates were in the form of thin platelets which produced displacement fringes parallel to their intersection with the surface (g·Rcontrast) and parallel moire´ fringe contrast. In addition they were strongly attacked by both HF and HNO3solutions. Diffraction patterns from the precipitates were indexed as from a base‐centered orthorhombic structure witha=6.3,b=3.8, andc=6.75 Å. The orientation relationship with the silicon matrix was [111] Si ‖ [011]p. The thin platelets appeared to be a partially coherent precipitate with an associated misfit vector of ∼⅓[111] such that the platelets compressively stressed the matrix. This compressive stress acts to partially relieve the diffusion‐induced tensile stress normal to the habit plane, and so the operating planes are those which are most perpendicular to the diffusion front so as to have the greatest possible resolved compressive stress in the diffusion front.

ISSN:0021-8979    

DOI:10.1063/1.1709016

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Microwave conductivity of semiconductors determined from transmission or reflection of the dominant mode of rectangular waveguide may contain a significant error caused by the impedance of the contact between the sample and the broad waveguide wall. This error increases with increasing bulk conductivity. The present paper describes a technique which eliminates this source of error by utilizing the TE01° mode of circular waveguide in a ``reflection coefficient bridge.'' Measurements of intrinsic germanium at 48 GHz show no contact influence over the conductivity range between 2 and 2×103mho/m. In contrast, the conductivity measured with a conventional rectangular waveguide transmission bridge saturates at about 50 mho/m.

ISSN:0021-8979    

DOI:10.1063/1.1709017

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Observations on small‐angle diffraction rings from very thin vapor‐deposited layers have been carried out using a direct‐recording electron diffractometer. The rings are due to the island structure of the deposited layers. A detailed correlation has been made between ring location and island/island interferences by statistical evaluation of electron micrographs. (The occurrence of inner diffraction rings from various types of specimens was first noted by Mahl and Weitsch using an electron‐microscope technique.)

ISSN:0021-8979    

DOI:10.1063/1.1709018

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The order‐disorder transformation in the alloy Cu3Au has been studied at pressures ranging up to 21 kbar by means of electrical‐resistance measurements made while the sample is at high temperature and under pressure. The rate of change of the critical temperature with pressure is 2.1°K/kbar from 7 to 21 kbar. The kinetics of the order transformation belowTcare adequately described by the homogeneous reaction rate equation and an activation volume of 6.8 cm3/mole of atoms. The magnitude of this activation volume indicates that the formation of vacancies on the gold sublattice is the rate‐limiting step in the homogeneous ordering process.

ISSN:0021-8979    

DOI:10.1063/1.1708937

出版商:AIP    

年代:1967

数据来源: AIP