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21.
Non-Gaussian photoluminescence peaks observed in a-Si:H-based structures at 6 K are interpreted as a consequence of the presence of different phases in material. Thin films of amorphous silicon deposited on glass substrate have been analyzed.The main aims of the contribution are (i) analysis of numerical data obtained by fitting procedure and (ii) formulation of corresponding conclusions in terms of structural properties of sample. Spectrum of a-Si:H-based samples can be interpreted as superposition of photoluminescence signals arising from two domains with different degrees of structural disordering. By our knowledge this result corresponds to real situation from view of structural properties of amorphous hydrogenated silicon. Under certain circumstances, decomposition of photoluminescence spectrum can give information of geometrical structure of sample. 相似文献
22.
We report on the size-dependent melting of prism-shaped nanoparticles based on thermodynamic model and applied to understand the melting of prism-shaped indium nanoparticles. It is shown here that the bulk melting temperature cannot be extrapolated from the nanoscale and the extrapolated value will always be lower than the bulk melting temperature as has been observed experimentally. 相似文献
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The use of a Carr-Purcell-Meiboom-Gill (CPMG) echotrain to increase the 29Si NMR sensitivity in glasses was investigated. The echo intensity decay follows a stretched exponential behavior M(t) = M0 exp[−(t/t2)β] with values for the exponent β in the range of 0.41-0.65. The signal to noise in the spectra can be increased by a factor of up to 4 by taking the weighted sum of the spectra obtained from the individual echoes. However, differential T2 relaxation for the different Qn species is observed, with a shorter relaxation time for Q4 than Q3. Thus, summing of the echoes leads to distorted spectral intensities and quantitative information can no longer be obtained from the spectra. To circumvent the problem with differential T2 relaxation, an alternative approach is developed in which the spectral intensity for each chemical shift value is determined from the stretched exponential fit to its echo decay. With this approach, the sensitivity can be increased by a factor of up to 2.4, while quantitative information can still be obtained from the spectra. The increased sensitivity permitted the detection of five-coordinated silicon in a potassium silicate glass with natural 29Si abundance at ambient pressure. 相似文献
24.
Bi2Te3 films and micro‐pillar arrays were electrodeposited, respectively, onto p‐Si(100) wafers and into micro‐templates that were etched on the same wafers with reactive ion etching (RIE). With the potentials of −100 to −300 mV (vs. saturated calomel electrode), Bi2Te3 films can be obtained from Bi3+ and HTeO solution, which showed a (001) preferential orientation. Micro‐templates with vertical holes of 15–18 µm in diameter and 40 µm in depth were etched on p‐Si(100) wafers, and then were set as cathodes. During electrodeposition, the SiO2 layer on the wafer surface served as an insulating layer, and Bi2Te3 only crystallized on the inner wall of etched holes. With the potentials of −300 to −700 mV, Bi2Te3 pillar arrays can be fabricated by filling electrodeposition, and the filling ratios and qualities were sensitive to the potentials. After removing the templates with RIE, the Bi2Te3 pillars can stand on the wafer surfaces. 相似文献
25.
Christian Schlaup Alexander Spaenig Peter Broekmann Klaus Wandelt 《physica status solidi (a)》2010,207(2):254-260
We describe the formation of thin copper sulfide semiconductor films under electrochemical conditions. In a first step we investigated the fundamental interaction of the Cu(1 0 0) surface with a sulfide anions containing electrolyte. Beside the classical p(2 × 2)‐S and c(2 × 6)‐S adlayer phases we found the formation of a closer packed “pseudo‐c(2 × 2)”‐S phase accompanied by an expansion of the topmost copper layer. For a further investigation of this “pseudo‐c(2 × 2)”‐S phase, we switched from the bulk Cu(1 0 0) electrode to a copper monolayer on a Au(1 0 0) electrode, which can be easily prepard using copper underpotential deposition. Since such a copper monolayer is pseudomorphic to the Au(1 0 0) surface and therefore expanded by 12.5% with respect to the bulk Cu(1 0 0)‐plane, exclusively a commensurate c(2 × 2)‐S structure is instantaneously formed and remains stable over a wide potential range. 相似文献
26.
Bernd Ahrens Philipp Lper Jan Christoph Goldschmidt Stefan Glunz Bastian Henke Paul‐Tiberiu Miclea Stefan Schweizer 《physica status solidi (a)》2008,205(12):2822-2830
Thermal processing of as‐made fluorozirconate glasses which were additionally doped with neodymium and chlorine ions leads to enhanced upconversion fluorescence intensities. The samples were annealed between 240 °C and 290 °C and the optimum value of upconversion intensity was found for the 270 °C sample. The development of glasses doped with Er, whose luminescence characteristics make it a better choice for application as an upconversion layer on silicon solar cells, is in progress. In addition, we present external quantum efficiency measurements of a silicon solar cell with a NaYF4:Er3+ upconverter. We also show a theoretical analysis where erbium transitions can be enhanced selectively to increase upconversion efficiency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The upconversion luminescence in Nd3+‐doped bismuth–borate glass, excited by 0.8 µm light, was studied in the visible spectral region. Four distinct emission bands were found. From their kinetics, two mechanisms can be shown to be responsible for all four lines: energy‐transfer upconversion, slightly dominating, and excited state absorption. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
29.
Diamond is an attractive electrode material to replace mercury, which has been the material of choice for the electrochemical analysis of heavy metals in solution using stripping voltammetry. As a solid electrode however, interactions between different metal analytes can occur at diamond, which are not observed at Hg electrodes. We therefore examine the associated effects arising in the analysis of two types of mixed metal ion solutions, Cu–Cd and Cu–Zn, using stripping voltammetry at diamond electrodes. The detection of Cu is shown not to be strongly affected by the presence of either of the other metals, but the presence of Cu blocks the signal which otherwise would be detected for the second metal, Cd or Zn. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
30.
C. S. Solanki R. R. Bilyalov J. Poortmans J.‐P. Celis J. Nijs 《physica status solidi (a)》2003,197(2):507-511
Formation and separation of thin porous silicon films from the original substrate in combination with the transfer of such films onto a cheap foreign substrate for the photovoltaic application provides a straightforward way to cost reduction. Separation of the porous silicon film from the reusable p+ silicon substrate is achieved by electrochemical etching of silicon under specific HF concentration and current densities. The effect of HF concentration on film separation is studied. It is found that film separation is possible only for HF concentration of 22% and lower. Addition of DI water in the solution results in the formation of a thick porous silicon layer without separation from the substrate during 10 minutes. A theoretical explanation has been given to describe the phenomena of porous silicon film separation. 相似文献