摘要:

Xe/I2low-pressure electric discharges are being developed as efficient, long-lived ultraviolet lighting sources. In this work the kinetics of low pressure, 0.5–5 Torr, radio-frequency inductively excited discharges sustained in Xe andI2were investigated to determine the source of radiating states. The diagnostics applied in this study include optical absorption and emission spectroscopy, microwave interferometry, and microwave absorption. We found that in time modulated discharges, the emissions from excited states of atomic iodine decays with time constants of hundreds of microseconds. These observations are consistent with those states being populated by ion-ion neutralization. Electron-ion recombination leading to excited states appears not to be an important source of emission.

ISSN:0021-8979    

DOI:10.1063/1.366022

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Minority-carrier lifetime damage coefficients for 1 MeV electron, 3 MeV proton, and 6 MeV alpha particle irradiation ofn-type (4.5×1015and1.3×1017 cm−3) andp-type(2.5×1017 cm−3)InP have been measured using time-resolved photoluminescence. These values are relatively insensitive to carrier type and show a slight increase with increasing carrier concentration. Evidence of comparable electron and hole capture lifetimes is found for the dominant recombination defect. The effect of 3 MeV proton and 6 MeV alpha particles relative to 1 MeV electrons is an increase in the lifetime damage coefficient by factors of about104and105,respectively. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366023

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effect of 1 MeV electron and 3 MeV proton irradiation on the performance ofn+pInP solar cells grown heteroepitaxially on Si (InP/Si) substrates is presented. The radiation response of the cells was characterized by a comprehensive series of measurements of current versus voltage(I–V),capacitance versus voltage(C–V),quantum efficiency (QE), and deep level transient spectroscopy (DLTS). The degradation of the photovoltaic response of the cells, measured under simulated 1 sun, AM0 solar illumination, is analyzed in terms of displacement damage dose(Dd)which enables a characteristic degradation curve to be determined. This curve is used to accurately predict measured cell degradation under proton irradiation with energies from 4.5 down to 1 MeV. From the QE measurements, the base minority carrier diffusion length is determined as a function of particle fluence, and a diffusion length damage coefficient is calculated. From theC–Vmeasurements, the radiation-induced carrier removal rate in the base region of the cells is determined. The DLTS data show the electron and proton irradiations to produce essentially the same defect spectra, and the spectra are essentially the same as observed in irradiated homoepitaxialn+pInP. From the DLTS data, the introduction rate of each defect level is determined. From the darkI–Vcurves, the effect of irradiation on the various contributions to the dark current are determined. The data are analyzed, and a detailed description of the physical mechanisms for the radiation response of these cells is given. The results enable a model to be developed for the radiation response of the cells. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366024

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Using high resolution electron microscopy and extensive image simulation, the atomic structure of the inversion boundaries has been determined in GaN layers grown on sapphire by electron cyclotron resonance assisted molecular beam epitaxy. They form nanometric domains (5–20 nm) limited by {101¯0} planes crossing the whole epitaxial layer. These small dimensions excluded the use of more conventional microscopy methods such as convergent beam diffraction for their characterization. For image simulations, up to 10 models including the well known Austerman–Gehman and Holt ones were considered for the boundary atomic structure. The overall agreement with the observed contrast was reached for a Holt type model of structure in which the boundary plane contains two wrong bonds per atom. Although the overall atomic configuration is neutral in {101¯0} boundary planes, it is expected to be highly energetic in ionic materials like GaN due to the difference in Ga–Ga and N–N bond length and local charge difference. This may probably explain the small size of the domains observed in the present samples. ©1997 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.366094

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The microstructure and electrical properties of buriedSiO2layers produced in silicon by the implantation of oxygen ions are analyzed in terms of implantation parameters and supplemental incorporation of oxygen. The buried oxides show inhomogeneous etching in aqueous HF, revealing the presence of a crystalline oxide phase and Si-enriched regions. Silicon enrichment inSiO2is found in the form of Si inclusions and oxygen deficient network defects. The former are found to be sensitive to the oxygen implantation profile, and may arise as a result of a blockage of Si outdiffusion by crystalline oxide inclusions. The network defects, in turn, are predominantly generated during high temperature postimplantation annealing, caused possibly by some mechanism of silicon transport from the interfaces into the bulk of oxide. The electron trapping and electrical conduction characteristics of buried oxides are found to correlate with the density and size of the inhomogeneities. By contrast, hole trapping and the generation of positive charge at the Si/oxide interfaces by exposure to hydrogen at elevated temperature are controlled by the network defects in the bulk of the oxide and in the near interfacial layers, respectively. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366025

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Cobalt–carbon thin films were deposited with a carbon concentration ranging from 27 to 57 at.&percent; at different substrate temperatures. The morphology and phases of as-deposited films were investigated by transmission electron microscopy and x-ray diffraction. The effect of annealing on the microstructure is reported. Under particular conditions of substrate temperature, carbon concentration, and subsequent annealing, a granular morphology consisting of nanocrystalline cobalt grains embedded in graphitelike carbon was obtained. The cobalt grains were uniform in size. The particle size could be controlled in the range from 4 to 7 nm by varying the carbon concentration. The cobalt phase was found to depend on the carbon concentration and substrate temperature. The hexagonal close-packed cobalt phase was observed only via the formation of the metastable carbide&dgr;′-Co2Cand its subsequent decomposition upon annealing. Otherwise the cobalt phase has a heavily faulted close-packed structure or a random stacking structure. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366026

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Surface modification of Al was studied by high current Fe-ion implantation using a metal vapor vacuum arc ion source. In the implantation process, two parameters were adjusted, that is, current density and ion dose, corresponding to varying the temperature and time for growing surface Fe-aluminide compound. The major hardening phase was identified to beAl13Fe4and its depth profile was found to depend on the current density and dose. At a fixed dose of3×1017 Fe/cm2,implanting with a low current density from 25 to51 &mgr;A/cm2,theAl13Fe4compound penetrated into a depth between 2500 and 4000 Å. Whereas implanting with a high current density up to101 &mgr;A/cm2,theAl13Fe4compound not only be situated in a 1000 Å surface layer, but also extended into a deep region when the dose was increased to1×1018 Fe/cm2.Another dual implantation was conducted with two different current densities and it resulted in a modified region of 4500 Å thick with a high concentratedAl13Fe4compound in a 1000 Å surface layer. Accordingly, the microhardness of the implantation treated Al films was considerably increased. The formation of the hardening phase ofAl13Fe4compound was responsible for the improvement of the surface mechanical property and was discussed in terms of temperature rise, irradiation time, and radiation-enhanced diffusion in the process of implantation. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366027

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

At present channeling is accepted to be the primary mechanism causing defects deep within dry-etched material, with diffusion possibly modifying the final defect distribution. In this article detailed analytic expressions are presented incorporating both these mechanisms. The dominant parameter affecting damage depth is found to be the mean channeling length. We show how enhanced diffusion, e.g., by illumination, may increase the observed damage. We also study the effect of damage on depletion depths and suggest how the channeling length may be inferred from the etch-depth dependence of conductance or Raman spectroscopy measurements. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366028

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

High-pressure shock Hugoniot data were measured for Be using strong shock waves generated by underground nuclear explosions. These data and a preliminary theoretical analysis are reported. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366029

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Boron (B), phosphorus (P), and arsenic (As) in-diffusion profiles were simulated based on an integrated diffusion model that takes into account the vacancy mechanism, the kick-out mechanism and the Frank–Turnbull mechanism. The simulations were done using just three parameters for B and P, and four parameters for As, each of which has a clear physical meaning and a physically reasonable value, with no additionalad hochypothesis. These parameters correspond to the diffusion of dopant species and of point defects that contribute to dopant diffusion. For the anomalous P diffusion profile, the vacancy mechanism governs the diffusion in the plateau region, while the kick-out mechanism governs it in the deeper region, where self-interstitials dominate in the kink region and P interstitials dominate in the tail region. This changeover from the vacancy contribution to the kick-out contribution is shown to be the mechanism for the appearance of the kink-and-tail profiles of P. Moreover, the comparison among B, P, and As diffusion is made to review the diffusion of these three dopants by means of a unified model. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366030

出版商:AIP    

年代:1997

数据来源: AIP