摘要:

Photoluminescence emanating from ``pure'' high resistivity SrTiO3has been examined between 4000 and 13 000 Å as a function of temperature and 3650 Å irradiation. One strong narrow peak (7929 Å at 95°K; half‐width ≤1 Å) and 9 associated peaks (7852, 8005, 8051, 8098, 8280, 8304, 8469, 8574, 8726 Å), each of which exhibit maximum intensity at 35° and 95°K, which are within the temperature ranges associated with the ferroelectric‐paraelectric transition, and the tetragonal‐cubic transition, respectively. As this emission extinguishes below 35°K, an asymmetric structureless broadband emission begins, which extends from ≈4200–≈8000 Å, and peaks near 5000 Å. Concurrent photocurrent measurements show: a maximum at 105°K and a minimum at 35°K; the existence of extensive trapping effects, including long‐duration (hours to days) dark‐current relaxation, a field‐induced persistent internal polarization (due to spacial separation of trapped electrons and holes), and an interaction between irradiation and ferroelectric hysteresis. Sublinear responses exist common to the photoluminescence peaks and photocurrents at various temperatures,viz.response ∝J&bgr;(T)where ½<&bgr;(T)<1. The behavior observed is in part interpretable on the basis of recombination processes via multiple defects.

ISSN:0021-8979    

DOI:10.1063/1.1709142

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A method has been developed for heating the electrons in a thermally generated alkali plasma by the resonant absorption of electromagnetic waves at the electron‐cyclotron frequency. The electron temperature was increased from 0.2 eV to ∼1.0 eV with the application of ∼1 W of power at a frequency of 10 kMHz. Excellent consistency has been found between diamagnetic measurements of plasma pressure, microwave determinations of plasma density, and double‐probe determinations of temperature. The observed temperature increases were in quantitative agreement with computations which consider the heat loss by thermal conduction.

ISSN:0021-8979    

DOI:10.1063/1.1709143

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The process of electron tunneling from a metal to a semiconductor through an insulating layer is considered. Theoretical current‐voltage expressions have been obtained, in particular, for the case when the semiconductor is degenerateptype and the conduction band of the insulator provides the dominant tunneling barrier. The existence of an energy gap and a relatively small Fermi energy in the semiconductor makes the current highly asymmetrical with respect to the polarity of the applied voltage. Experimentally, junctions of Al‐Al2O3‐SnTe and −GeTe have been fabricated and theirI‐Vcharacteristics measured at 4.2°K. Good agreement is observed between the theoretical and experimental current behavior, from which energy parameters of the semiconductors and the barrier relations of the junctions have been obtained.

ISSN:0021-8979    

DOI:10.1063/1.1709144

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The theory of the scattering of light by ringed two‐dimensional spherulites containing biaxial crystals oriented at an arbitrary angle to the radius and helicoidally rotating about the radius is developed. The presence of intensity maxima at various scattering angles is predicted in patterns which are similar to those which are experimentally observed.

ISSN:0021-8979    

DOI:10.1063/1.1709145

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Chemical reversibility of the nitrosyl chloride photodissociative laser is achieved by addition of a large excess of chlorine which also serves as an efficient buffer gas, and thereby eliminates the need for helium. Consideration is given to the prospect of utilizing this system as a means of converting solar radiation to monochromatic coherent emission.

ISSN:0021-8979    

DOI:10.1063/1.1709146

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The effect of hydrostatic pressure onp‐njunctions of Si and GaAs in which both ideal and generation‐recombination currents were present has been investigated. It is shown that the pressure coefficients of the energy gap can be obtained directly from the pressure‐induced shifts in the forward‐bias voltage, measured at a constant total junction current. Presently determined pressure coefficients of −1.5±0.005×10−3eV/kbar for Si and 10.9±0.1×103eV/kbar for GaAs are in good agreement with values obtained for Si and GaAs by other methods. In the case of GaAs, the pressure‐induced shift in the forward‐bias voltage reverses sign when the conduction‐band minimum shifts (to the [100] valleys) at high pressure.The effect of pressure on the reverse breakdown voltage for Si junctions has also been determined. The results seem to offer some support to the theory of Hauser and Wortman.

ISSN:0021-8979    

DOI:10.1063/1.1709147

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The present paper describes reflection and transmission of a plane electromagnetic wave by a dielectric half‐space which is moving uniformly perpendicular to the plane of incidence. It is found that for the incidentEplane wave both the reflected and transmitted waves are no longer anEplane wave but a linear combination ofEandHplane waves. In addition, it is shown that for the incidentEwave theE‐wave components of the reflected and transmitted waves carry a positive power, but the power flow with regard to theH‐wave component of the transmitted wave is always negative while the power carried by theH‐wave component of the reflected wave is always positive.

ISSN:0021-8979    

DOI:10.1063/1.1709148

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The temperature dependence of the ferromagnetic resonance linewidth of highly polished single‐crystal spheres of EuS was measured in the range from 2.2° to 30°K, using standard microwave techniques at a frequency of 22.65 GHz. The linewidth increases from ∼5 Oe at 2.2°K to ∼400 Oe at the Curie point, and continues to increase in the paramagnetic range to a value of 1000 Oe at 78°K. The linewidth varies linearly with reciprocal magnetization from 2.2° to 18°K, as predicted by the Landau‐Lifshitz equation and can be characterized by a temperature‐independent microphysical damping constant, &lgr;, equal to 1.9±0.09×108rad/sec within this temperature range.

ISSN:0021-8979    

DOI:10.1063/1.1709149

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Electron densities have been measured in the subsonic portion of a free‐expansion argon jet by microwave and Langmuir‐probe methods. Microwave phase‐shift measurements were made with an interferometer in such a way that the spatial variation of electron density could be determined. The data were analyzed with a ray‐tracing technique.Langmuir‐probe measurements were made with cylindrical and flat probes under essentially collision‐free conditions, and over a range of probe radius to Debye length ratios of about 10–50. Both electron and ion collection were measured and analyzed. Three methods of analyzing the electron‐current part of the characteristic were compared. It was found that one method gave values two or three times higher than another method. The discrepancy was due to the failure of the experimental Langmuir‐probe characteristic to follow the theoretical one in the vicinity of plasma potential: the so‐called ``knee'' of the curve. This difficulty has been overcome by analyzing the data with the aid of theoretical particle‐collection curves.

ISSN:0021-8979    

DOI:10.1063/1.1709150

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Calorimetric measurements on a sample of TiNi (50 at.%) show that the heat‐capacity maximum at approximately 87°C represents a higher‐order transition. The transition was shifted to lower temperatures each time the material was heated through the transition from slightly above room temperature to about 150°–200°C. The transition enthalpy decreased in three such cycles from 4150 to 3375 J/mole TiNi.

ISSN:0021-8979    

DOI:10.1063/1.1709151

出版商:AIP    

年代:1967

数据来源: AIP