摘要:

1‐MeV electron irradiation damage inn+‐pjunction InP solar cells has been studied as a function of irradiation temperature, in comparison with those in GaAs cells. Solar cell property degradation of InP solar cells due to electron irradiation has been found to strongly decrease with an increase in irradiation temperature while that in GaAs cells is independent of irradiation temperature up to 150 °C. These results are explained by thermal annealing phenomena of radiation‐induced defects in InP solar cells. The irradiation temperature dependence of radiation damage in InP cells has been analyzed based on annealing characteristics of radiation‐induced defects, determined by deep‐level transient spectroscopy measurement, in InP. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358606

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A tentative model which reveals the existence ofp‐type regions with a significant spatial extension in eitherp‐ orn‐type fast neutron irradiated high‐purity germanium is presented. This model is based on transient capacitance spectroscopy data. The regions described here are present after room‐temperature neutron irradiation in a material with a preirradiation free‐carrier concentration at 77 K of around 1011cm−3. They are characterized by the presence of a high concentration of point defects. Previous measurements show that these point defects act as shallow and deep acceptors. Simple calculation allows the estimation of the shallow acceptor concentration inside these regions from experimental data as well as the average size of such high defect density regions. The microscopic origin of the point defects located in these regions is also discussed. The data gives some basic insight into the properties of defects induced by displacement cascades in elemental semiconductors. Despite some limitations in the quantitative approach, this study also provides new elements for the understanding of neutron induced defects in lightly doped germanium. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358607

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Refractory metal silicides, namely NbSi2, TaSi2, WSi2, and MoSi2, were successfully synthesized by using a metal vapor vacuum arc (MEVVA) ion source to implant the respective metal ions with high current density into Si(111) and Si(100) wafers. The implantation was conducted at room temperature with an extracted voltage of 40 kV. When the current densities of the refractory metal ions were up to 65 &mgr;A/cm2, the equilibrium hexagonal NbSi2and TaSi2phases were formed at an implantation dose of 3×1017ions/cm2, while the hexagonal WSi2and MoSi2phases were formed at a dose of 5×1017ions/cm2. With increasing the current density up to 90 &mgr;A/cm2, the transition of the hexagonal WSi2and MoSi2phases to their most stable tetragonal structures was observed. Postannealing at 750 and 950 °C resulted in the formation of the unique tetragonal WSi2and MoSi2phases, respectively. The electrical property of the MEVVA‐synthesized refractory metal silicides was measured for both as‐implanted and postannealed wafers. In addition, the formation of the refractory metal silicides by MEVVA implantation is discussed in terms of the beam heating effect caused by high current ion implantation. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359537

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Channeling implantations of 20 keV boron into silicon have been performed with doses between 1013and 1016cm−2in the [100], [110], and [211] direction, and parallel to a (111) plane. Simulations using an empirical electronic stopping model agree very well with the experimental results. The model has been obtained considering a large number of random and channeling implantations published in the literature. It contains a nonlocal and an impact parameter dependent part with the nonlocal fraction increasing with energy. Moreover, a computationally efficient damage accumulation model is presented which takes point defect recombination into account. It is found that due to interactions within a recoil cascade only 1/8 of the generated damage is stable, and that damage saturation takes place at a concentration of 4×1021cm−3. Comparison of simulations and experiments indicates that displaced atoms reside on random positions rather than on tetrahedral interstitial sites in the silicon lattice. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358608

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Carefully prepared and well‐characterized Bi1.7Pb0.3Sr2Ca2Cu3Oxsamples were studied by means of differential scanning calorimetry, thermogravimetry, and room and high temperature x‐ray diffraction in different atmospheres. It is found that the decomposition of Bi1.7Pb0.3Sr2Ca2Cu3Oxstrongly depends on the given conditions. In argon atmosphere, the sample begins to decompose at 850 °C, and finally decomposes mainly into Bi2Sr2CuOx, Cu2O, CaO, and (Sr,Ca)2O3; in air, it decomposes at 880 °C, into Bi2Sr2CuOx, Bi2Sr2CaCu2Ox, Bi1.7Pb0.3Sr2Ca2Cu3Ox, and (Sr,Ca)O; in oxygen, it decomposes at 900 °C, into Bi2Sr2CuOx, Bi2Sr2CaCu2Ox, Bi1.7Pb0.3Sr2Ca2Cu3Ox, and (Sr,Ca)2O3. The process of the melting wasinsitustudied by high temperature x‐ray diffraction and a quenching method. This study gives some hints for growing single crystals of Bi1.7Pb0.3Sr2Ca2Cu3Oxand how to introduce pinning centers into Bi2Sr2CaCu2Oxand Bi1.7Pb0.3Sr2Ca2Cu3Ox. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358609

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Anomalous depth distributions of bulk microdefects (BMDs) are observed in Czochralski silicon wafers subjected to two‐step annealing [(550–700 °C)×t1+(850–950 °C)×t2, wheret1andt2=1–100 h]. The number density of BMDs near the surface is smaller than that in the bulk whent1is short, and is larger whent1is long. The anomalous distribution extends deeper than 100 &mgr;m from wafer surfaces and cannot be explained by the behavior of interstitial oxygen atoms. Distributions are examined under various annealing conditions, such as annealing temperature, rate of temperature ramping, ambient atmosphere, and initial oxygen concentration. The anomalous distributions are found to be formed in the early stage of second‐step annealing only when the annealing starts with a rapid temperature rise. A formation model of anomalous distributions is proposed based on the following assumptions: (1) self‐interstitials exist in the thermal equilibrium state, (2) wafer surfaces are a permanent source and sink of self‐interstitials, (3) growing oxygen precipitates produce self‐interstitials, and (4) self‐interstitial undersaturation enhances stable growth of precipitate nuclei, and supersaturation suppresses stable growth. The nonequilibrium self‐interstitial concentration induced in the bulk after the rapid temperature rise is responsible for the anomalous distributions. All the experimental characteristics are reasonably explained by the model. The formation process of the anomalous distributions is detected by three‐step annealing experiments. Basic properties of self‐interstitials in silicon are extracted from experimental results combined with the model. The activation energy for migration is about 2.5 eV. The diffusion coefficient is about 10−6cm2 s−1at 900 °C. The thermal equilibrium concentration is estimated as about 1012cm−3at 1000 °C. These results are close to recent experimental estimates utilizing impurity diffusion in floating zone silicon. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.358610

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The article presents a study of the interaction of iron with a grain boundary in boron‐doped multicrystalline silicon. The sample was intentionally contaminated with iron to a few 1014cm−3and investigated by the electron‐beam‐induced‐current technique (measurement of minority‐carrier diffusion length, quantitative imaging) in the temperature range 80–300 K. The measurements were carried out for two different states of iron in the sample: (i) iron paired with boron, i.e., as FeB, and (ii) iron as interstitial iron Fei. The differences between diffusion lengths for these two states were used to estimate the iron concentration. The analysis of the data revealed a pronounced iron profile around the grain boundary, indicating gettering of about 4×1011iron atoms per cm2. The recombination velocity of the grain boundary is about 5×105cm s−1at 300 K and is not changed by the FeB destruction treatment. The temperature dependence of the iron‐related diffusion length components is discussed and found to be in satisfactory agreement with what is expected from Shockley–Read–Hall theory. Further, the diffusion length analysis revealed also a strong recombination channel of unidentified origin. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358611

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Silicon powders produced in a low pressure silane plasma show varying structural properties depending on the location of collection of the powders in the reactor. This is revealed by high resolution transmission electron microscopy, infrared and Raman spectroscopy. The particulates are found to consist either of heterogeneously distributed amorphous and crystalline phases or of nanoscale particles with amorphous and molecular like spectral features as found from the Raman spectroscopic studies. Infrared spectra show clustered silicon‐hydrogen phases and the presence of oxidized phases in the powder, upon exposure to atmosphere. Phonon confinement effects due to the nanometer size and expansive strain is observed in the vibrational Raman spectra. The average particle size estimated from the observed phonon quantum confinement corresponds with the particle sizes observed by high resolution electron microscopy if strain contributions are included. Annealing at temperatures as low as 300 °C leads to Raman vibrational band similar to crystalline silicon. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358612

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The conditions necessary for obtaining both the maximum topographical image contrast and the maximum insensitivity to ion induced damage using ion‐beam induced charge microscopy are presented and interpreted in terms of existing energy loss and damage theory. Ion‐beam induced charge images and pulse‐height spectra which are measured from a Sandia SA3002 memory device using MeV H+, H+2, and4He+ions with a range of incident energies are used to characterize these optimum experimental conditions. It is shown that ions which are stopped within the device depletion layers generate charge pulses which are much less sensitive to ion induced damage than longer range ions which are stopped in the device substrate. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358613

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Free‐standing 4‐&mgr;m‐thick Al thin films were prepared by partially removing the Si substrate after deposition of the film. The tensile film stress was determined from the membrane vibration frequency in the temperature range between room temperature and −190 °C. The flow stress of the free‐standing films is compared to that of substrate‐bonded ones deposited under identical conditions thus having basically the same microstructure. It was found that the flow stress of the unsupported films agrees with that of bulk Al (when extrapolated to the same grain size of 1–4 &mgr;m) being considerably smaller than that of substrate bonded films. This directly proves the importance of the film/substrate interface for the yield strength of substrate‐bonded metallic films supporting existing theoretical models. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358546

出版商:AIP    

年代:1995

数据来源: AIP