摘要:

As‐deposited undoped microcrystalline silicon (&mgr;c‐Si:H) has in general a pronouncedn‐type behavior. Such a material is therefore often not appropriate for use in devices, such asp‐i‐ndiodes, as an active, absorbingilayer or as channel material for thin‐film transistors. In recent work, onp‐i‐nsolar cells, this disturbingn‐type character had been successfully compensated by the ‘‘microdoping’’ technique. In the present letter, it is shown that thisn‐type behavior is mainly linked to oxygen impurities; therefore, one can replace the technologically delicate microdoping technique by a purification method, that is much easier to handle. This results in a reduction of oxygen impurities by two orders of magnitude; it has, furthermore a pronounced impact on the electrical properties of &mgr;c‐Si:H films and on device performance, as well. Additionally, these results prove that the unwanted donor‐like states within &mgr;c‐Si:H are mainly due to extrinsic impurities and not to structural native defects. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117440

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Ion implantation of Si (60 keV, 1×1014/cm2) has been used to introduce excess interstitials into silicon predoped with high background concentrations of B, which were varied between 1×1018and 1×1019/cm3. Following post‐implantation annealing at 740 °C for 15 min to allow agglomeration of the available interstitials into elongated {311} defects, the density of the agglomerated interstitials was determined by plan‐view transmission electron microscopy observation of the defects. We report a significant reduction in the fraction of excess interstitials trapped in {311} defects as a function of boron concentration, up to nearly complete disappearance of the {311} defects at boron concentrations of 1×1019/cm3. The reduction of the excess interstitial concentration is interpreted in terms of boron‐interstitial clustering, and implications for transient‐enhanced diffusion of B at high concentrations are discussed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117441

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An optically recording velocity interferometer system, ORVIS, was developed for measurements of the time evolution of the free surface and the particle velocity in laser induced shock waves experiments. This system produces interference fringe shifts which are proportional to the Doppler shift of a laser beam reflected from the moving surface. These fringe shifts are recorded with a high speed electronic streak camera, which has a 70 ps time resolution. Using this method, the free surface velocity was measured with an accuracy better than 5% and the pressure in laser shocked aluminum targets was calculated. Shock waves of order of hundreds of kilobars are produced by a Nd:YAG laser system with a wavelength of 1.06 &mgr;m, pulse width of 5 ns (FWHM) and energy in the range (30–50) J, focused to spots diameters in the range (200–1000) &mgr;m. The dynamic spall strength reported here for Al is (14.47±1.45) kbar for a strain rate of &Vegr;˙∼8×106s−1, consistent with studies performed with other methods. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117587

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Oxidation of partially Ga‐terminated Si(111) surfaces with clean 7×7 striped areas along atomic step edges was investigated using scanning reflection electron microscopy. Molecular oxygen exposure of 100 L at the substrate temperatures of 410 °C oxidized Ga atoms on the Ga‐terminated areas as well as Si atoms on the clean 7×7 areas. The Ga oxides were selectively desorbed over the Si oxides during annealing. This results in the formation of stripe‐patterned Si oxides on the surface. After growth of an 8‐monolayer Si film and subsequent annealing, Si grooves with a depth of about 1 nm and a width around 200 nm were formed along the step edges by excess Si‐assisted thermal desorption of the Si oxides. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117588

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report significant differences between the properties of buried oxides converted from AlGaAs and AlAs layers using selective wet oxidation. Layers of AlxGa1−xAs withx≥0.96 exhibit crystallographic dependent oxidation rates, while for layers withx≤0.92 the oxidation rate is isotropic. Mesas containing partially oxidized layers of AlAs are unstable to rapid thermal cycling and exhibit excessive strain at the oxide terminus, while mesas containing partially oxidized layers of AlGaAs are robust and lack evidence of strain. Finally, the oxidation of AlGaAs layers, rather than AlAs, is found to provide robust oxide apertures for reliable vertical‐cavity surface emitting lasers. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117589

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Europium‐doped KCl1−xBrxmixed crystals have been studied as a selective ultraviolet (UV) detector material in the actinometric region (200–300 nm). Thermoluminescence glow curves of room‐temperature UV‐irradiated samples were analyzed as a function of compositionxand irradiation wavelength. A thermoluminescence enhancement, relative to the pure KCl and KBr end components is found; for 210–300 nm irradiation the KCl40Br60:Eu2+solid solution presents a significant increase in thermoluminescence efficiency. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117590

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Although the solubility of Cu in Cr is negligible in the equilibrium state, Cu precipitates were discovered in extensively cold‐rolled Cr ribbons of Cu‐15 wt % Crinsitucomposite by means of analytical transmission electron microscopy (TEM) and high‐resolution electron microscopy (HREM). The precipitation sequence was found to be a Cu‐rich cluster ⇒ Cu GP zone ⇒ Cu equilibrium phase. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117591

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

High crystalline quality epitaxial metal/insulator superlattices composed of Ti1−xAgx(0.03<x<0.06) and MgO have been grown on MgO(001) substrates at 273 K by electron beam evaporation in ultrahigh vacuum. X‐ray diffraction measurements and cross‐sectional high‐resolution transmission electron microscopy measurements revealed that the crystal structures of the TiAg alloy and MgO in the superlattices were tetragonal and that the superlattices were so‐called strained‐layer superlattices. The x‐ray rocking curve was measured around one of satellite peaks in the middle angle range, and showed the full width at half‐maximum of the curve was 0.04°–0.05°. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117592

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Dopant activation occurs via both thermal annealing and light‐soaking in boron‐doped hydrogenated amorphous silicon–carbon prepared at a relatively low temperature. Both kinds of dopant activation probably originate from the same boron sites, because they both cause almost the same increase in dark conductivity, and no light‐induced activation occurs after the thermally induced activation has been attained. The light‐induced states show relaxation even at room temperature and are bistable sites, but the thermally induced states show no significant relaxation and have a more stable configuration. Perhaps, the light‐induced states are caused by microscopic change and the thermally induced states are created with larger scale restructuring. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117593

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Silica film has been produced at room temperature by a single precursor process of photolitic chemical vapor deposition using a newly developed Xe excimer lamp. Tetraethoxyorthosilicate (TEOS) has been used as a raw material. Transparent thin film of SiO2was obtained on single crystalline Al2O3substrates and its properties were evaluated by means of the reflection Fourier transformation‐infrared spectroscopy, the scanning electron microscopy, and ultraviolet‐visible spectrometry. Consequently, it was found that the main component of the film was SiO2and very small amounts of residual organic materials were contained. It was also found that the film was very dense and the refractive indices were only 1.7% smaller than that of bulk silica glass. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117594

出版商:AIP    

年代:1996

数据来源: AIP