摘要:

The surface properties of the anodized oxide/InSb system have been studied using metal‐oxide‐semi‐conductor structures. It was found that the surface state charges are negative in general. This negative surface charge comes from the following two sources: the acceptor‐type surface state on the real InSb surface and the positively charged trap levels in the oxide. There is also evidence that two sets of trap levels exist in the oxide, with relaxation time as the characteristic difference. The Electron Microprobe Analyzer was employed in this investigation to evaluate the chemical composition in the oxide as well as in the surface layer of InSb. This was achieved by regulating the accelerating voltage to control the depth of electron penetration.

ISSN:0021-8979    

DOI:10.1063/1.1659187

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Consideration of simple variations of a basic resistive‐network model for an inhomogeneous material shows that a wide variety of experimentally observed effects can be described with respect to equilibrium or steady‐state Hall and thermoelectric measurements. The correlation between these macroscopic Hall and thermoelectric measurements and the microscopic electrical and geometrical properties of the material is derived. A suitable combination of both Hall and thermoelectric measurements on the same sample makes it possible to determine the dominant average microscopic and geometric parameters of the system. Although developed under the stimulus of research into the photoconductivity mechanism in chemically deposited lead sulfide layers, the results of the consideration may have a wider application.

ISSN:0021-8979    

DOI:10.1063/1.1659188

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Various transport studies have been carried out on amorphous and crystalline GeTe films of 80 Å to 10 &mgr; thickness. Crystalline GeTe has a low resistivity (∼10−4&OHgr;·cm at 300°K) which increases with temperature slowly and nearly linearly at low temperatures (below ∼300°K) and rapidly at higher temperatures. The hole concentration (N∼1010−1021cm−3) increases only slightly with temperature. Mobility varies asN−4/3. These results in conjunction with the tunnel‐spectroscopy and optical data show that crystalline GeTe is a degenerate (and thus metallic conduction),p‐type narrow band gap (∼0.1–0.2 eV) semiconductor with Fermi level ∼0.3–0.5 eV inside the valence band. The linear increase of the susceptibility mass with hole concentration, the constancy of the Hall coefficient up to&ohgr;L&tgr;=0.35 (&ohgr;L=Larmor frequency, &tgr;=collision relaxation time), and the monotonic increase of thermopower with temperature indicate that conduction takes place only in a single valence band. Amorphous GeTe films exhibit activated conduction. The dc resistivity varies from 410° to 77°K as &rgr;0exp (Eg/2kT), whereEgis about 0.8 eV and &rgr;0is the resistivity of crystalline GeTe films. Ac resistivity decreases with frequency (&ohgr;) as &ohgr;−n, wherenlies between 0.5 and 1.0, depending on the temperature. The activation energy for ac conduction decreases rapidly from the dc value to zero with decreasing temperature as well as increasing frequency. The capacitance of amorphous GeTe at 77°K varies as &ohgr;−0.2while the loss factor is independent of the frequency. With increasing dc field, the linear dependence of current on voltage changes to a power relationVn, wherenvaries rapidly from ∼3 to 6 or more in a small range of the applied field. At very high fields,I∝exp&bgr;F1/2(&bgr;=constant) is observed. These results, together with the tunnel‐spectroscopy, and optical data suggest that amorphous GeTe may be represented as ap‐type semiconductor with band gap ∼0.8 eV with exponential tailing of the bands and a continum of localized states in the vicinity (both sides) of the band edges. Conduction takes place by two parallel processes of intrinsic excitation across the band gap, and thermally and/or field‐assisted hopping from one localized (trapping) state to another. Dc conduction by hopping at low fields is negligible. At higher fields, trap modified space‐charge‐limited current flow and Poole‐Frenkel effect determine the nonlinear field dependence of current.

ISSN:0021-8979    

DOI:10.1063/1.1659189

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The effect of shock stress amplitude and duration on the hardness and microstructure of Hadfield steel has been investigated over the pressure range of 5–480 kbar. Electron microscopy techniques were used to examine the microstructure and measure the dislocation density of shock loaded specimens. Stacking fault and twin fault probabilities were estimated from x‐ray diffeaction experiments. For a given peak shock stress the time duration of the stress pulse greatly affected the hardness and microstructure of the shocked material. The Hugoniot equation of state of Hadfield steel is reported for shock stresses of 5–500 kbar.

ISSN:0021-8979    

DOI:10.1063/1.1659190

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

This work deals with the effect of radio‐frequency waveform on the resolving power of an aperiodic rf mass spectrometer. The expressions for the energy‐gain function and resolution from one‐ to five‐stage analyzer configurations have been obtained with five different waveforms of the rf signal. The improvement of the resolving power obtained with square‐wave over sine wave excitation has been illustrated graphically for all the five configurations of the analyzer assembly. The effect of adding second harmonic to the sine wave, on the resolving power, has been investigated. The influence of inaccuracies in the grid‐positioning on the resolving power with sine and square‐wave operations has been discussed.

ISSN:0021-8979    

DOI:10.1063/1.1659191

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The nucleation rate of gold on the cleavage face of muscovite mica in UHV was studied as a function of substrate temperature for 403°–515°K and of impinging flux for 0.6–1.8×1013cm−2sec−1. This range of substrate temperature and flux values was selected to yield growth conditions consistent with analysis of the nucleation rate data in terms of the atomistic nucleation theory of Walton. Gold was evaporated from a wire maintained at a temperature below the gold melting point and positioned near the mica substrate so that various regions on the mica were exposed to different fluxes with accurately known relative values. The mica was subsequently thinned and examined by transmission electron microscopy to determine the initial nucleation rate. The low‐temperature nucleation rate data gree reasonably well with the atomistic nucleation theory of Walton, while the high‐temperature data show two peaks in nucleation rate.

ISSN:0021-8979    

DOI:10.1063/1.1659192

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A clear pattern of systematic error is found in thermal expansion values for Al, Ag, and Au commonly recommended and used as internal references for temperature determination in x‐ray diffraction. Evidence comes from a critical analysis of the literature, including several studies of temperature measurement errors in powder cameras, and from new calibration of a thermometer used previously in precise lattice and length expansion studies. Necessary changes in the commonly accepted values for expansion of Pt and MgO are implied.

ISSN:0021-8979    

DOI:10.1063/1.1659193

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

An analytical investigation of the thermoelectric effect of hot carriers in semiconductors with non‐parabolic energy bands and spherical energy surfaces has been carried out. The analysis is good for moderately high intensities of the applied electric field. Some numerical results, particularly applicable to indium arsenide and indium antimonide, are presented at the end.

ISSN:0021-8979    

DOI:10.1063/1.1659194

出版商:AIP    

年代:1970

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1659195

出版商:AIP    

年代:1970

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1659196

出版商:AIP    

年代:1970

数据来源: AIP