摘要:

Using available, or easily borrowed, equipment we have constructed an ac system for measuring thermopower. With this system we have measured the thermopower of a gold‐aluminum thermocouple from 30 to 150°C with accuracy of a few percent, using a temperature difference of 0.03 K. With care, and the proper equipment, measurements accurate to about 1% appear possible, using a temperature difference smaller than 0.01 K.

ISSN:0034-6748    

DOI:10.1063/1.1684751

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

An apparatus is described for studying high current density bombardment of semiconductors. It operates at voltages up to 30 kV and samples can be cooled to 28 K. The excitation density is high enough to induce lasing in many II‐VI and III‐V compounds at both 77 K and room temperature. The emission spectrum over a range of current densities is useful in characterizing the doping and impurities in semiconductors.

ISSN:0034-6748    

DOI:10.1063/1.1684752

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A split sphere apparatus has been developed to generate exceedingly high hydrostatic pressures more than 300 kilobars at temperatures over 1500°C in a sample chamber of ample volume. The calibration of pressures is made by the use of known phase transition points in Bi, Fe, and Pb. The calibration above the Pb point (161 kilobars) is discussed in terms of resistance changes for In and CdS previously reported by Drickameret al.

ISSN:0034-6748    

DOI:10.1063/1.1684753

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A technique for determining p‐n junction doping profiles is presented. The doping level distribution is determined from a series of surface‐barrier capacitance (SBC) measurements, using the recently developed continuous impurity plotter (CIP) [J. A. Copeland, IEEE Trans. Electron DevicesED‐16, 445 (1969)]. The SBC measurements are made on an array of Schottky barrier diodes deposited on a 3° angle‐lapped junction. The effective spatial resolution normal to the junction is 5 &mgr;. This method yields a higher resolution than the four‐point probe method, requires less time than the step layer capacitance technique, and is more accurate than either method. In general, it is the most efficient approach to determining accurate junction impurity profiles presented to date. To illustrate the utility of the technique, an impurity doping profile is determined for an n‐on‐p liquid‐phase epitaxy GaP diode.

ISSN:0034-6748    

DOI:10.1063/1.1684754

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

An operational amplifier has been combined with a resistance bridge to obtain the properties of a four terminal conductance bridge which is suitable for electron tunneling measurements. The advantages and limitations of the system are described and illustrated.

ISSN:0034-6748    

DOI:10.1063/1.1684755

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

This paper reports several research applications of time shared computers. It has often been claimed that time shared computers cannot be used effectively in research. It is found that, for a large range of experiments in physics, the time shared computer is ideal. Use of a time shared system is less expensive, more interactive, more versatile, and much faster than on‐line computer systems. Use of time shared systems is more interactive than batch processing computer facilities. Experimental results are described from a wide range of experiments. The experiments concern plasma waves in solids, color centers in the ultraviolet, and electron tunneling measurements of ir impurity bands in insulators. The results reported demonstrate the wide versatility of the computer experiment system in such areas as data reduction, data smoothing, graphing, and plotting.

ISSN:0034-6748    

DOI:10.1063/1.1684756

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A constant false alarm rate closed loop controls avalanche photodiode bias over varying operating conditions such as temperature or ambient illumination and changes in photodiode parameters. The photodiode output is amplified, sensed in a threshold circuit, shaped to a constant amplitude and duration, and integrated. The integrator, also fed by a constant current representing the desired false alarm rate, generates an output proportional to the integrated error in false alarm rate. This control signal alters the photodiode bias until the integrated false alarm rate error is zero.

ISSN:0034-6748    

DOI:10.1063/1.1684757

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

An event triggered spectrograph shutter with a speed of 70 m·sec−1has been constructed and used to study shock tube plasmas. The shutter can simultaneously serve two high aperture spectrographs. Several sequential exposures of 8–150 &mgr;sec can be obtained over a period of 300 &mgr;sec. Jitter in opening and exposure times is 6–8%. Delay times can be varied mechanically in a simple and predetermined way.

ISSN:0034-6748    

DOI:10.1063/1.1684758

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Two methods have been developed for synthesizing diffraction line profiles from continuous scanning data. The first method uses numerical analysis where segments of profiles are approximated by one or more polynomials. The second method employs Fourier analysis to obtain the Fourier coefficients of the diffraction profile from continuous scanning data. Examples of application are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1684759

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

In pulsed nuclear magnetic resonance a random variation of the nutation angle is produced if the rf pulse initiation occurs at a random phase with respect to the rf carrier. The effect is most important at low resonance frequencies and large rf pulse amplitudes. An approximate calculation of the rms variation is presented, and a circuit is described which minimizes the variation by synchronizing the rf pulse with the rf phase.

ISSN:0034-6748    

DOI:10.1063/1.1684760

出版商:AIP    

年代:1970

数据来源: AIP