摘要:

Thin carbon foils have become integral parts of low‐energy particle detectors in forthcoming space experiments. In these devices, the foil acts as electron source for signal generation. Since 10–20‐eV photons can also generate electrons from these foils and since intense HL&agr; and Heiresonance lines prevail in space environment, forward photoemission yield in carbon foils must be investigated. Crabon foils of 2.0, 7.0, and 14.0 &mgr;g cm−2thickness (density 1.35 g cm−3) are subjected to 121.6‐nm or 10.2‐eV photons and 58.4‐nm or 21.2‐eV photons and the corresonding forward photoemission yield and transmittance are obtained. Energy distributions of photoemitted electrons are also measured.

ISSN:0021-8979    

DOI:10.1063/1.327849

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The photoluminescence (PL) technique has been used in the analysis of heat‐treated silicon crystals to investigate the origin and the behavior of thermally induced defects. The PL measurements were made at liquid helium and liquid nitrogen temperatures on various groups of commercial wafers which were subjected to an isochronal annealing at a temperature between 450 and 1250 °C for 64 h. The PL results were compared with the results obtained by other characterization techniques, in particular, the infrared (IR) spectroscopy. After heat treatment at 450 °C, a new PL pattern appeared at 4.2 K, if the crystal contained a high concentration of oxygen. The new pattern is proved to be associated with the thermally induced donors. The PL and IR results classified Czochralski‐grown wafers into two categories. Various heat treatments made a great change in the PL spectra for some wafer groups (category I), but a little change for the other wafer groups (category II). Correspondingly, the decrease in the interstitial oxygen concentration due to annealing was large for category I and small for category II. The PL intensity reduction at lower temperatures (600<T<900 °C) was closely correlated with the formation of silicon‐oxygen complexes. It can be concluded that the Si‐O complexes is produced with greater ease in category I than in category II. The variation in the configuration and/or the density of the Si‐O complexes may induce the PL spectral change. Possible factors which separate the two categories are residual carbon and the thermal history of the crystal.

ISSN:0021-8979    

DOI:10.1063/1.327850

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

CdTe/Hg1−xCdxTe multilayers (0.3<x<0.5) were obtained for the first time by a liquid phase epitaixal (LPE) technique. The layers were grown on (111)A oriented CdTe substrates. The surface morphology of these multilayers is similar to those of HgCdTe single layers reported before. The cross diffusion at the CdTe/Hg1−xCdxTe interface has been as small as 0.3 &mgr;m for the thin CdTe epilayer. The first CdTe/HgCdTe heterojunction sensitive to ∼2.8 &mgr;m at 77 K has been demonstrated.

ISSN:0021-8979    

DOI:10.1063/1.327851

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Field effect studies on MIS structures of silver‐glassp‐type InSb have been made in the temperature range 77–300 K. It has been observed that the effect of negative gate voltage is to decrease the Hall coefficient, Hall mobility, and grain boundary barrier potential, while the effect of positive gate voltage is opposite but less significant. The results can be explained in terms of accumulation and depletion layers, induced on the surface.

ISSN:0021-8979    

DOI:10.1063/1.327852

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Curent suppression in Al0.35Ga0.65As‐GaAsN‐pheterojunctions is observed experimentally. The data are explained by examining the carrier transport modified by electron accumulation in the interface potential notch resulting from the conduction‐band discontinuity. In addition, it is found that the temperature dependentI‐Vmeasurements can be used to deduce the magnitude of &Dgr;ECat the junction interface.

ISSN:0021-8979    

DOI:10.1063/1.327853

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Optical second‐harmonic generation at 1.06 &mgr;m was demonstrated in the cubic (4¯3m) and orthorhombic (mm2) phases of Cr‐Cl, Cu‐Cl, Fe‐I, and Ni‐Br boracite. The discontinuous change in the second‐harmonic intensity is consistent with the known first‐order nature of the ferroelectric phase transition. Both phases of boracites are suggested to be non‐phase‐matchable for second‐harmonic generation and for cubic boracites; indirect methods result in nonlinear optical coefficients (d123=d213=d312) in the range (0.20 to 0.26) ×10−9esu. in the range (0.20 to 0.26)×10−9esu.

ISSN:0021-8979    

DOI:10.1063/1.327854

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The influence of the tripropylamine content in the CO2laser gas mixture on the spatial distribution of electrons produced by photoionization has been studied. The data, obtained for a standard CO2TEA laser uv source, indicate that two processes are involved in the mechanism of tripropylamine photoionization. Photoabsorption parameters for both processes have been found.

ISSN:0021-8979    

DOI:10.1063/1.327855

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Absorption characteristics for LiF, BaF2, CsI, KCl, KRS‐6, and SiO2have been measured by laser calorimetry in order to estimate the transparency limit. Weak absorption tails, which differ from the Urbach tail, were observed to follow an exponential law. It is found that the weak absorption tail indicates the transparency limits for these materials.

ISSN:0021-8979    

DOI:10.1063/1.327856

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A self‐focused electron beam produces a string of hot spots along its path in 0.35 Torr of air. In this communication we report some interesting snap shots on the luminous gas bubbles expanding from the pinched hot spots. The radial speed of expansion is measured to be ∼9 mm/&mgr;sec, which corresponds to ∼6 eV of kinetic energy per N+ion.

ISSN:0021-8979    

DOI:10.1063/1.327857

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The microdefect distribution in dislocation‐free floating‐zone silicon crystals has been investigated by means of preferential etching. The etch structures developed on the microdefects are found to depend upon the presence of dopants and the surface treatment of the crystal sections. Strong indications were obtained that microdefects in chemically–mechanically polished slices are saturated with atomic hydrogen, developed during the polishing treatment, and which affects the etching behavior of the microdefects in a different way than hydrogen that dissolved in the crystal during the growth process. Low concentrations of dopants appeared to suppress the effect of hydrogen introduced during polishing.

ISSN:0021-8979    

DOI:10.1063/1.327858

出版商:AIP    

年代:1980

数据来源: AIP