摘要:

A systematic experimental study shows that the Hall mobilities of electrons at 77 K over the entire accessible range of electron densities in VPE GaAs films grown under high‐purity conditions are below the theoretically predicted values. At a given electron concentration the experimental mobilities are independent of the preparation parameters (As/Ga ratio, dopant element, dopant pressure, growth temperature). Most of the literature data, not only on VPE but also on LPE and MBE films, appear to be in good agreement with these results. This finding casts some doubt on the idea that all such layers are electrically compensated.

ISSN:0021-8979    

DOI:10.1063/1.324381

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Diffusivities and emissivities are measured through the use of the transient technique for five metals. Diffusivity values for Al, Ag, Cu, Fe, and Ni are found to be 0.89, 1.73, 1.14, 0.216, and 0.176 cm2/sec, and respective emissivity values are found to be 0.23, 0.031, 0.038, 0.046, and 0.054. These diffusivities agree well with other values in literature and differ from values previously obtained through use of this technique because of corrections for heat reflection and possibly better heat input techniques.

ISSN:0021-8979    

DOI:10.1063/1.324382

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Taking a simple branching process as model of the carrier multiplication in reverse junctions, the turn‐on probability of a microplasma is determined. Considering the variation of the voltage and current in the diode, the distribution of the off‐state time interval is deduced. Finally, expressions for the amplitude distribution as well as the rate of discharges in units of time are developed in the case where the on‐time is negligible.

ISSN:0021-8979    

DOI:10.1063/1.324383

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Spontaneous current emission has been observed while heating polyvinyl chloride (PVC) above room temperature. The dependence of this current on various factors including the effects of different metal electrodes have been investigated. Possible mechanisms for such spontaneous currents are discussed.

ISSN:0021-8979    

DOI:10.1063/1.324385

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The effect of heat treatment in various environments on the electrical and optical properties of indium–tin oxide (ITO) sputtered films has been investigated. As the resistivity is decreased by heat treatment in H2from 8.3×10−3to 4.3×10−4&OHgr; cm, the optical band gap increases from 3.05 to 3.42 eV consistent with a Burstein shift and intrinsic band gap of 2.98 eV, and for resistivities less than 8.3×10−4&OHgr; cm there is a rapid decrease in transmission at longer wavelengths due to free‐carrier absorption and formation of dendritic precipitates. Careful control over all sputtering variables is essential to obtain reproducible properties.

ISSN:0021-8979    

DOI:10.1063/1.324386

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The attenuation and phase velocity of a superconducting thin‐film stripline are calculated at high frequencies using the theory of Mattis and Bardeen. These results are used to study the propagation of picosecond pulses which have frequency components approaching the superconducting energy‐gap frequency.

ISSN:0021-8979    

DOI:10.1063/1.324387

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An explicit model of contact‐charge exchange in polymers is proposed in which the steady‐state exchanged charge resides in intrinsic molecular‐ion states. The eigenvalue spectra of these states are inferred from metal/polymer contact‐charge measurements using a theoretical formalism constructed for this purpose. This model of metal/polymer contact‐charge exchange is extended to encompass the description of polymer/polymer contact‐charge exchange as well. Utilizing the metal/polymer contact‐charge‐exchange spectra as input data, the model predicts correctly both the sign and order of magnitude of measured contact‐charge exchange between polystyrene and copolymers of styrene and methyl methacrylate.

ISSN:0021-8979    

DOI:10.1063/1.324388

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A surface region about 0.22 &mgr;m thick of cadmium‐annealed undopedn‐type CdTe single crystal was converted toptype by implantation of 60‐keV As+ions followed by a cadmium annealing. The electrical properties of thep‐type layer were measured as well as the photovoltaic properties of thep‐njunction formed in this way. For illumination by sunlight an open‐circuit voltage of 0.84 V was found in a cell with a solar efficiency of 3.0&percent;. The parameters of the junction were determined using a model designed to describe the spectral response of the cell.

ISSN:0021-8979    

DOI:10.1063/1.324389

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

V3Ga has been prepared as a single‐filament wire by the solid‐state reaction of a composite consisting of a vanadium 10.1 at.&percent; aluminum alloy core in a bronze matrix of copper 16.7 at.&percent; gallium. Reaction temperatures varied from 525 to 750 °C. Reacted layer thicknesses are found to increase as (reaction time)1/2. Rates of layer growth and activation energies are compared for a variety of starting composites. The addition of Al to the core enhances the rate of growth of the V3Ga layer, particularly at temperatures below 600 °C. Aluminum is incorporated within the V3Ga layer to the extent of 2–7.5 at.&percent;. The superconducting transitions have onset temperatures of 15.0–15.3 K, with midpoints of 14.0–14.6 K. The (paramagnetically limited) upper critical fields at 4.2 K are 21–22 T. Critical‐current densities were measured up to the critical field and approach those of Howe and Weinmann for material with gallium in the core. The form of the dependence of pinning force on field differs from that of Howe and Weinmann’s specimens in which a different pinning mechanism must operate.

ISSN:0021-8979    

DOI:10.1063/1.324390

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The difference in the stress for plastic deformation between the mixed state and the superconducting state has been measured in a series of lead‐indium crystals. These measurements show that the change in drag stress between the two states varies in the same manner as does the ultrasonic attenuation in a type‐II superconductor. Quantitative agreement between the present results and Maki’s theory of transport properties in dirty superconductors is found for higher solute concentration crystals. These results show that dislocation motion in these lead‐indium alloys can be treated as an underdamped oscillator.

ISSN:0021-8979    

DOI:10.1063/1.324391

出版商:AIP    

年代:1978

数据来源: AIP