摘要:

We studied thin films of cuprous oxide deposited on glass coated with transparent conducting indium–tin oxide (ITO) films. The deposition of both Cu2O and ITO was made by rf sputtering in an Ar/O2gas mixture. For the deposition of Cu2O a pure copper target was used and ITO films were deposited from a disk target, the halves of which were made of Sn and In, respectively. This allows variation of the stoichiometry of the deposited ITO film by changing the position of the substrate glass beneath the Sn/In target. X‐ray diffraction of Cu2O films indicates the typical pattern of amorphous material. We were able to produce Cu2O films of different stoichiometry by varying the O2to Ar ratio during rf sputtering. The maximum resistivity of the films corresponds to an ideal stoichiometry of Cu2O. An activation energy of 0.55 eV found from thermostimulated conductivity is related to excess Cu vacancies. The band gap found from the spectral dependence of the photovoltaic effect is 2.0 eV. The composition of ITO films was studied by Auger analysis and can be described as a variable composition mixture of SnO2+xand In2O3+y. To produce an Ohmic electrode, gold was evaporated on the top of the Cu2O film and hence the resulting structure of the photocell could be specified as ITO–Cu2O–Au, for which we propose a barrier band diagram. We studied the photovoltaic characteristics of the fabricated photocells under an incandescent lamp with &bartil;100 mW/cm2output. The open‐circuit voltage and short‐circuit current of our cells were about 20–90 mV and 50 &mgr;A/cm2, respectively, and some dependence of the output characteristics on the composition of ITO film was observed. Conversion efficiency for thin films Cu2O/ITO cells was found to be substantially lower than for Cu2O/Cu Schottky barrier cells. This is tentatively attributed to small diffusion lengths and/or presence of interface recombination centers.

ISSN:0021-8979    

DOI:10.1063/1.332427

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Estimates of the location and strength of electrical sources in the brain can be made using the magnetoencephalogram (MEG) which is the measurement of the brain’s magnetic field. Since the size and configuration of the field‐sensing coils used in MEG detectors can affect these measurements, the effects must be known and taken into consideration in making these estimates. This paper uses computer modeling methods to determine the effects of coil size and configuration on measurements of a dipolar source in a spherical model of the head. The measurements are as follows: a magnetometer, which uses a single coil; a first‐order, in‐line gradiometer, which uses two coils at different distances from the head; and a first‐order, side‐by‐side gradiometer, which uses two side‐by‐side coils at the same distance from the head. For the magnetometer it is found that the effects of coil size are large enough that the source depth can be overestimated by as much as 0.65 cm and its strength underestimated by as much as 31%. For the in‐line gradiometer, the effects of the back coil on measurements of sources near the surface of the sphere are small as compared to the effects of the finite size of the front coil; for deeper sources, the effects are found to be large but nearly independent of the size of the back coil. For the side‐by‐side gradiometer, the effects of coil size are large enough that the dipole depth can be overestimated by as much as 0.45 cm and its strength underestimated by as much as 37%. In addition, the effects of tilting the two coils used in the side‐by‐side gradiometer are investigated. It is found that this tilting does not cause the measurements to be more localized over the source. Finally, the effects of coil size on estimates of source depth made from side‐by‐side gradiometer measurements of the falloff of field amplitude with distance from the sphere are determined. It is found that the effects are large enough to cause the depth to be overestimated by as much as 0.5 cm.

ISSN:0021-8979    

DOI:10.1063/1.332428

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Approximate expressions are derived for the density and temperature variations in a pulsed discharge laser. The analysis is specialized to the case of the electron‐beam‐excited CO2laser. In particular, a procedure is suggested for including the refractive index variations in computer codes modeling loaded resonator characteristics of high‐power pulsed lasers.

ISSN:0021-8979    

DOI:10.1063/1.332429

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Continuous‐wave (cw) lasing behavior has been observed with 1.3‐&mgr;m InGaAsP lasers grown on (311) and (511) InP substrates. Threshold current densities of (311) devices were 30% lower than those on comparable (100) devices (1000 vs 1300 A/cm2). The photoluminescence intensity fromp+–InGaAsP ‘‘cap’’ layers is more than an order of magnitude greater than on (100) devices.

ISSN:0021-8979    

DOI:10.1063/1.332430

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

GaAs/(GaAl)As channeled‐substrate laser with deep Zn diffusion for tight current confinement is reported. It has extremely low threshold current (as low as 12 mA), high differential quantum efficiency, single lateral and longitudinal mode operation up to 10 mW. It hasT0of about 200 °C and the rate of threshold current change is only about 0.07 mA/°C from 10 to 70 °C.

ISSN:0021-8979    

DOI:10.1063/1.332431

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

From energy balance the pinch ratiorp/r0(whererp= equilibrium pinch radius andr0= original radius) may be directly computed for the case of a constant current electromagnetic pinch. For the case of a varying current, to solve the energy integral requires the current as a function of the pinch radius. To achieve this an approximate pinch trajectory is first estimated using a snow‐plow model. This trajectory by itself gives a zero pinch ratio but it enables the energy integral to be performed. The theoretically predicted values ofrp/r0for several cases are found to be in satisfactory agreement with experimental values. This procedure would be useful for designers of pinch devices.

ISSN:0021-8979    

DOI:10.1063/1.332432

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We have studied the laser‐enhanced nucleation of oxidation‐induced stacking faults in ion‐implanted silicon. Silicon ions of 100 keV were implanted onto the silicon surface in the dosages ranging from 1.0×1013to 1.0×1014cm−2. The laser beam used was 1.06 &mgr;m in wavelength with a diameter of 40 &mgr;m, and was generated from aQ‐switched Nd:YAG laser at a repetition rate of 12 kHz and a 150‐ns pulse width. It was found that the laser irradiation enhanced the generation of oxidation‐induced stacking faults or their generation nuclei through the implantation‐induced lattice defects at the boundary between the laser scanned and nonscanned regions. Laser‐enhanced nucleation is caused by the supersaturation of the silicon self‐interstitials generated by the rapid heating‐cooling cycle induced by laser irradiation reacting with the self‐interstitials induced during oxidation.

ISSN:0021-8979    

DOI:10.1063/1.332433

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Compressibility studies have been carried out on Ge–I (diamond‐cubic structure) to 12.0 GPa; the results are in very good agreement with previous work. We confirm the recent report of a substantial lowering of the Ge I–II transition pressure in a nonhydrostatic pressure environment. We observe the Ge–II (200)‐peak at 10.5±0.2 GPa in a more hydrostatic pressure environment and as low as 6.7 GPa when shear stresses are present. On release of pressure from above 11 GPa, we find that Ge–II converts predominantly into Ge–III when Ge–I and shear stresses are present and completely into Ge–III in the absence of Ge–I in a more hydrostatic pressure environment. This is contrary to what had been previously presumed.

ISSN:0021-8979    

DOI:10.1063/1.332434

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Previously, an exact calculation was made for the temperature dependent density of states effective mass inp‐type silicon. This calculation was made for the nondegenerate regime and included the full nonspherical‐nonparabolic nature of the valence band structure. For those researchers interested in using this mass for the analysis of their transport data we offer a polynomial fitted expression. The values generated are within 1% of the theoretical values.

ISSN:0021-8979    

DOI:10.1063/1.332397

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The neutralization of deep‐level centers associated with palladium and platinum in silicon after exposure to a low‐pressure hydrogen plasma has been observed using transient junction‐capacitance spectroscopy. Inn‐type silicon, a palladium‐related level atEc−0.22 eV and platinum‐related level atEc−0.28 eV were neutralized by a low‐temperature (300 °C) plasma treatment. Inp‐type silicon, a palladium‐related level atEv+0.32 eV was also neutralized by this treatment, but a platinum‐related level atEv+0.33 eV was unaffected by hydrogen plasma exposure. Possible mechanisms for the observed reduction in defect electrical activity are discussed.

ISSN:0021-8979    

DOI:10.1063/1.332398

出版商:AIP    

年代:1983

数据来源: AIP