摘要:

Selenium‐arsenic alloys undergo a photochemical reaction when exposed to radiation of band‐gap energy or greater. The influence of this photoinduced reaction on the electrophotographic photosensitivity of amorphous arsenic triselenide films was studied. A progressive change in the short‐wavelength photoresponse was seen in films which were exposed to intense light. The characteristics of the change depend upon the substrate temperature during the vacuum deposition of the film. Films prepared at substrate temperatures belowTginitially showed an increase in sensitivity, possibly due to structural relaxation or molecular rearrangement within the film. The initially measured spectral sensitivity of films prepared belowTgwas always lower than that for films prepared nearTg. All films eventually showed a reduction in short‐wavelength sensitivity. The rate of this change increased at elevated temperatures. The photolytic reaction itself does not affect the photosensitivity. The reduction in photosensitivity is a result of the oxidation and subsequent depletion of arsenic at the surface of the photoconductor which is enhanced by the prior photodissociation of the arsenic triselenide.

ISSN:0021-8979    

DOI:10.1063/1.324612

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Spectra are presented from flowing afterglows in N2produced by a microwave discharge. The luminescence from pure N2discharges can be characterized as a typical Lewis‐Rayleigh afterglow with no molecular emission in the ultraviolet. Trace amounts of SF6added upstream of the discharge greatly enhance the first‐positive emission from the afterglow and produce intense emission from the N+2first‐negative system and the appearance of N2second‐positive emission. Further SF6addition downstream of the microwave discharge quenches the N+2first‐negative bands but causes no appreciable change in the emission from the N2second‐positive bands. Increasing the SF6added prior to the discharge by a factor of 15 results in complete quenching of all N2ultraviolet emission which is replaced by NSB‐Xluminescence.

ISSN:0021-8979    

DOI:10.1063/1.324613

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Oxygen contamination in sputter‐deposited Nb films was measured as a function of background pressure and other sputtering variables using Auger electron spectroscopy. Significant variables affecting purity were the degassing rate and the ultimate background pressure prior to sputtering. Serious contamination occurred even when the background pressure was in the 10−10‐Torr range. Getter sputtering within a cryogenically cooled container with the appropriate sputtering variables can reduce contamination to a level nearly identical to that of the target material.

ISSN:0021-8979    

DOI:10.1063/1.324614

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The distribution of vibrational states which are excited by resonant radiation and deactivated by a relaxation process is strongly influenced by the anharmonicity of the molecule and the red shifting of the resonant frequency. Steady‐state distribution curves are calculated for the BCl3molecule, the &ngr;3mode of which is resonant to CO2laser light. A flux of states is defined for these distribution functions which is recognized as the rate for photochemical reactions. Some results are given for photodissociation, which show that proper detuning of the light can increase the rate of photodissociation by several orders of magnitude.

ISSN:0021-8979    

DOI:10.1063/1.324615

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Recently 12&percent; efficient indium tin oxide (ITO) on silicon solar cells have been reported. Experiments indicate the presence of a thin interfacial insulating layer. Thus, these devices appear to belong to a class of semiconductor‐insulator‐semiconductor (SIS) solar cells where one of the semiconductors is a degenerate wide‐band‐gap oxide. We have developed a theory in terms of minority‐carrier tunnel current transport through the interfacial layer where one semiconductor is in a nonequilibrium mode. The wide‐band‐gap semiconductor serves to block band‐to‐band majority‐carrier current and thus, in principle, give better device performance than with an MIS solar cell. The effects of interfacial layer thickness, substrate doping level, surface states and interface charge, temperature on the performance of SIS solar cells have been calculated. These indicate that real‐world ITO on silicon cells should be able to achieve 20&percent; efficiency under AMl illumination. Other combinations of semiconductors would yield even better performance.

ISSN:0021-8979    

DOI:10.1063/1.324616

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

CdS/InP and CdS/GaAs heterojunctions were prepared by aninsituH2S/H2etching process and H2transport of CdS onto the InP and GaAs substrates. The etching involves a reaction of the III‐V compound surface to the corresponding sesquisulfides and simultaneous or subsequent removal by reduction in H2gas. The etching process changes the junction characteristics considerably. The junction onp‐GaAs shows a pinning of the Fermi level at the interface approximately 0.75 eV above the GaAs valence band. The junction onn‐GaAs is Ohmic.

ISSN:0021-8979    

DOI:10.1063/1.324617

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A qualitative model describing grain‐boundary effects in polycrystalline heterostructure solar cells is presented. Two salient observations of the model are (1) that an accumulated grain boundary in the light‐absorbing layer can produce a surface field that serves to reduce grain‐boundary recombination and increase device short‐circuit current and (2) that the grain boundary in either the window layer or absorber layer should be depleted so as to avoid high device tunneling currents. Avoiding high tunneling currents leads to high device open‐circuit voltages. The model describes additional electrical effects and suggests means of controlling and characterizing grain‐boundary types.

ISSN:0021-8979    

DOI:10.1063/1.324618

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Earlier results for guided electromagnetic waves on buried cables are recast in terms of internal and external impedances. Then it is possible to deduce the excited cable current in terms of the applied axial electric field. Explicit numerical data are presented for low frequencies when the outer cable diameter is small compared with the electrical skin depth of the surrounding earth. Of particular importance is the remarkable fact that the deduced attenuation rate and phase velocity of the dominant transmission mode depends only slightly on the burial depth of the cable.

ISSN:0021-8979    

DOI:10.1063/1.324619

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The diffusion‐bonding method has been applied to the fabrication of aC‐band (6.5‐GHz) superconducting Nb cavity of TM010mode. The cavity consists of two parts which are machined from a reactor‐grade solid billet of Nb. The two parts are electropolished and joined in an ultrahigh‐vacuum induction furnace by applying mechanical pressure of about 1.7 kg/mm2. For the bonding, it takes about 10 h at 1900 °C in 10−7–10−8Torr. A tension test shows that the tensile strength of the joint is more than 24.4 kg/mm2. The cavity, which is vacuum annealed in the same furnace and lightly electropolished, shows an unloadedQas high as 1.1×109at 1.3 K in the rf field region of 0–7 G. The maximum surface field as high as 321 Oe and 22.7 MV/m is obtained. These results are compared with those obtained for cavities fabricated by the electron‐beam welding method.

ISSN:0021-8979    

DOI:10.1063/1.324620

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The behavior of NbTi superconductors under dynamic mechanical stress was investigated. A training effect was found in short‐sample tests when the conductor was strained in a magnetic field and with a transport current applied. Possible mechanisms are discussed which were proposed to explain training in short samples and in magnets. A stress‐induced microplastic as well as an incomplete pseudoelastic behavior of NbTi was detected by monitoring acoustic emission. The experiments support the hypothesis that microplastic or shape memory effects in NbTi involving dislocation processes are responsible for training. The minimum energy needed to induce a normal transition in short‐sample tests is calculated with a computer program, which gives the exact solution of the heat equation. A prestrain treatment of the conductor at room temperature is shown to be a simple method of reducing training of short samples and of magnets. This is a direct proof that the same mechanisms are involved in both cases.

ISSN:0021-8979    

DOI:10.1063/1.324621

出版商:AIP    

年代:1978

数据来源: AIP