摘要:

The conductivity and Hall coefficient of evaporated InSb films 550 to 3750 Å thick have been monitored while the films were being annealed. It is found that the conductivity passes through a maximum during annealing, if the temperature is above 130°C. The Hall coefficient remains very small while films are annealed at temperatures below 200°C, but it rises rather abruptly at a fixed higher temperature, approaching some asymptotic value after several hours. Evidences of free In and Sb shown by electron and x‐ray diffraction of unannealed films are no longer present after the films are annealed at 130°C. Electron microscope examination of carbon replicas reveals no gross differences between the surfaces of annealed and unannealed films and shows that the films are continuous. Annealed films of both conductivity types have been observed. At room temperature, carrier concentrations lie between 6×1015and 4×1019/cm3and Hall mobilities between 10 and 500 cm2/V sec. The mobility increases with increasing temperature over most of the range from 100 to 500°K; in a few cases it has passed through a maximum near the high temperature limit.

ISSN:0021-8979    

DOI:10.1063/1.1729011

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Resistivity data as a function of temperature and composition have been obtained for solid solution alloys of &bgr;‐AgCd and &bgr;‐AuCd. Silver substitution for gold in &bgr;‐AuCd produces a lowering of the temperature of the diffusionless transformation and changes the nature of the transformation for the higher cadmium concentration alloys. Small substitutions of gold for silver in &bgr;‐AgCd also lower the transformation temperature while larger substitutions raise it. Ordering of gold and silver near the composition AgAuCd2has been observed by x‐ray diffraction and confirmed by residual resistivity measurements. This ordered structure is identical to that of the Heusler alloy; at lower temperatures ordered AgAuCd2transforms to a more complex phase. Separate disorderings involving the gold‐silver sublattice and the cadmium sublattice have been observed. Away from the composition AgAuCd2, residual resistivity measurements show the expected parabolic behavior. Some of these phenomena can be qualitatively explained in terms of ion‐core and electro‐negativity differences.

ISSN:0021-8979    

DOI:10.1063/1.1729012

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Iron films having thicknesses of 20, 100, and 250 Å were deposited from the vapor in a vacuum of about 2×10−5mm Hg at a rate of deposition of approximately 8 Å/sec onto Formvar substrates initially at room temperature and onto silica substrates initially at 50°C. Prior to deposition the latter were baked‐out at 500°C for 1 h. Transmission electron diffraction patterns of the specimens were examined with a microphotometer and no evidence of fiber orientation was found. These experiments were repeated with films being deposited at pressures of 10−2and 10−1mm Hg of helium introduced into the system after initial evacuation of the system to about 2×10−5mm Hg. Again random orientation was observed for both the Formvar and silica‐backed films. Comparison of the conditions characterizing this work with those describing similar work in which a fiber texture did occur leads to the formulation of the hypothesis that if the experimental technique does not include at least one of two conditions (high deposition rate, high substrate/deposit surface temperature), then fiber orientation is not likely to occur in thin (<1000 Å) iron films deposited onto amorphous substrates, but only in thick films for which prolonged exposure to the radiant source eventually sufficiently elevates the surface temperature. A qualitative description of the processes involved is suggested.

ISSN:0021-8979    

DOI:10.1063/1.1729013

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Electrical conductivity and the Seebeck coefficient of Bi8Te7S5have been measured in the two main crystallographic directions of the rhombohedral lattice, parallel and perpendicular to the hexagonal (basal) plane. The ratio of the two electrical conductivities has a value of 7.56 at liquid nitrogen temperature. The Hall effect along the basal plane has been measured. The properties change with temperature in a manner that indicates a complicated degenerate conduction band.

ISSN:0021-8979    

DOI:10.1063/1.1729014

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An ultrasonic wave traveling in certain directions in a piezoelectric semiconductor such as cadmium sulfide can be amplified or attenuated by application of a dc electric field. The direct current flowing through the medium in the presence of an ultrasonic wave creates a traveling ac field which interacts with the ultrasonic wave. Amplification occurs when the drift velocity of the electrons exceeds the velocity of sound. For strongly piezoelectric semiconductors, amplification of as much as several percent per wavelength of path is obtainable. Calculations show that for properly prepared material, significant amplification is expected up to the microwave frequencies. At high frequencies, gain is reduced because electron diffusion smooths out the electron bunching necessary for amplification. The dc power required increases rapidly with frequency, and at frequencies above one or two thousand megacycles only pulsed operation seems feasible. Applications as a tool in ultrasonic studies, and for devices such as delay lines and amplifiers, are also discussed.

ISSN:0021-8979    

DOI:10.1063/1.1729015

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Crystalline germanium films were grown epitaxially by vacuum evaporation of germanium onto heated fluorite substrates. In the work reported here, the effect of substrate temperature during film evaporation on the crystallinity and electrical properties of the films has been explored. Thirty &OHgr;‐cmp‐type germanium was evaporated in a conventional bell jar at pressures between 10−5and 10−4mm Hg. The germanium was evaporated from a resistance‐heated tantalum boat onto a fluorite plate. Substrate temperatures varied from 470° to 915°C, while the rate and duration of evaporation was held constant at about 1500 Å/minute and two minutes, respectively.The crystalline nature of the films was studied by electron diffraction. The transition from a nearly amorphous film at 470°C to a nearly single‐crystal film at 915°C was observed. Hall coefficients and electrical conductivities were measured for the films, which wereptype as was the starting material. These results are presented along with the mobilities and carrier concentrations calculated from them. The mobilities increase rapidly with film evaporation temperature. Carrier lifetimes were found to be less than 1 &mgr;sec in the most crystalline film, whereas the original germanium had a carrier lifetime of about 12 &mgr;sec.

ISSN:0021-8979    

DOI:10.1063/1.1729016

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A theoretical treatment is presented of the behavior of various components of the electromagnetic field generated by a horizontal electric dipole, embedded in a homogeneous conducting half‐space, and excited by a step‐function current. Displacement currents are neglected, thereby limiting the validity of the treatment to frequencies that are not too high, while the results for the transient response are only valid for sufficiently large times after the application of the step function to the dipole. The treatment is based on Laplace transform theory. Besides the electric and magnetic components in the conducting medium, also the vertical electric field in aire0zat points at the interface is examined. Since the expressions obtained are rather involved, numerical results are given only fore0zand a horizontal magnetic component in the conducting mediumh1x. The response ofe0zis a pulse with a rise time proportional to the square of the antenna depth but independent of horizontal distance, and a long trailing edge. The magnetic componenth1xrises slowly to a stationary value; its rise time increases with increasing horizontal distance. It is shown that there is a marked difference in attenuation with depth, and sometimes also with horizontal distance, between transient and sinusoidal signals.

ISSN:0021-8979    

DOI:10.1063/1.1729017

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An attempt has been made to measure the rate of change of superconducting transition temperatureTc, as a function of surface charge density &sgr;, in tin films. For films having thicknesses of 190, 670, and 1460 Å, |dTc/d&sgr;| was found in all cases to be less than 30 deg cm2C−1, the limit of sensitivity of the present apparatus. This negative result is compared with Glover and Sherrill's finding that in a tin film 70 Å thick,dTc/d&sgr; = −460 deg cm2C−1.

ISSN:0021-8979    

DOI:10.1063/1.1729018

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An interpretation of previous experiments on the movement of charged dislocations in ionic crystals is given. It is shown that those experiments involving bending do not allow an unambiguous determination of the sign of the charge to be made and the contradictory results obtained from indentation experiments can be resolved on the assumption that the dislocations carry a positive charge.

ISSN:0021-8979    

DOI:10.1063/1.1729019

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Longitudinal modes in the output of pulsed U: CaF2and ruby optical masers have been observed directly by means of a high resolution, high‐dispersion grating spectrometer. The mode spacings are in reasonable agreement with the expected values. The linewidth of the individual modes is instrument‐limited at about 0.05 cm−1. Maser action is observed to occur simultaneously in the various modes.

ISSN:0021-8979    

DOI:10.1063/1.1729020

出版商:AIP    

年代:1962

数据来源: AIP