关键词： Amorphous alloys  

摘要： The elastic scattering cross section for Be-9(alpha,alpha)Be-9 has been measured in a strongly resonant region from 6.00 to 6.50 MeV at a laboratory angle of 177 degrees. This reaction has been used to investigate Be diffusion in the bulk metallic amorphous alloy Zr41.2Ti13.8Cu12.5Ni10Be22.5 in the solid state (SS) as well as in the supercooled liquid slate (SLS). Above the glass transition, i.e., in the SLS, a remarkable increase in the diffusivity of Be (about two orders of magnitude over a 40 K temperature interval) was observed, which can be explained with a modified Arrhenius fit, which takes into account the change in configurational entropy due to the glass transition.

关键词： disordered systems   electronic states (localized)   spin-orbit effects   electron paramagnetic resonance  

摘要： The dangling bond spin relaxation times in a-Si:Ge:H alloys are determined with pulse electron spin resonance techniques as a function of alloy composition and temperature. Over a wide alloy range two spin lattice relaxation components are detected in saturation recovery measurements. The two components are attributed to Si- and Ge- dangling bond states. It is found that the respective relaxation times, which in the pure alloys are different by two orders of magnitude due to the difference in the spin orbit coupling of Si and Ge, both gradually change with alloy composition but maintain largely different values also in the alloys. As a function of temperature the relaxation times decrease as T--m (m approximate to 2). Copyright (C) 1996 Published by Elsevier Science Ltd

关键词： Semiconducting germanium compounds  

摘要： The valence band and Ge3d core-level structure of amorphous germanium-nitrogen alloys (a-Ge1-xNx) of various compositions (0 < x < 0.36) have been studied by ultraviolet photoelectron spectroscopy using He I and He II excitation. Two N-related bands centered at about 11 and 5 eV below the Fermi energy are found to evolve in the valence band spectra with increasing x. These are attributed to N2p bonding and lone-pair states, respectively. A systematic shift and broadening of the Ge3d core level peaks occurs with increasing x. Analysis of this effect allows for the determination of a N-induced chemical shift per Ge-N bond of 0.30 +/- 0.08 eV. For x > 0.22, a significant recession of the top of the valence band sets in, which is correlated by the sudden increase of the optical gap. An asymmetrical widening of the band gap for x > 0.22 is deduced.

关键词： Silicon solar cells  

摘要： Experiments of electric bias effect on a-Si:H and a-SiGe:H solar cells are carried out in both diode and triode configurations. In triode mode, positive bias on substrate improves the performance of a-Si:H cells, while zero bias the gives best results for a-SiGe:H cells. In diode mode, there is essentially no effect of bias on the cells observed over the voltage range in our experiments.

关键词： Amorphous alloys  

摘要： A systematic study of the deep defect related electronic transitions on a series of device quality amorphous silicon-germanium alloys (a-Si,Ge:H) produced by the glow discharge method uas carried out. The experimental results indicate a unique defect structure in these alloys;specifically, a deep defect band below the Fermi level and a clear majority carrier trap distribution above the Fermi level. More significantly, a defect band disclosed by sub-bond-gap spectroscopy exhibits a strong relaxation effect, which suppress the electron thermal emission. It is believed that band may act as a 'safe electron trap' to enhance the lifetime of the minority carriers.

关键词： brazing   titanium alloy  

摘要： Ti-6Al-4V alloy was induction brazed with 25Ti-25Zr-50Cu amorphous filler metal using argon as a shielding gas. The brazing cycles were rather short: RF inductor power was supplied for only 40-60 s. The tensile strength and ductility of the brazed joint are at the level of that of Ti-6Al-4V base metal. According to SEM/EDAX and STEM phase analysis, two main joint microstructures are observed: either a very fine lamellar/cellular eutectoid consisting of mixture of alpha-Ti + gamma-(Ti,Zr)(2)Cu tetragonal MoSi2 type phase or martensitic alpha-Ti with dispersed gamma-phase. The final copper concentration in the joint area is considered one of the critical parameters for joint microstructure formation. The optimal. eutectoidal microstructure characteristic of a ductile joint is obtained under brazing conditions that should result in average copper joint concentration within the 10-12 wt.% range. It is also found that the postbrazing natural cooling rate of 12.5 mm diameter rod samples is sufficient to suppress the formation of undesirable brittle lambda-Cu2TiZr Laves phase appearing in vacuum furnace brazing due to inherently low cooling rates. A variety of metallurgical paths along which base and filler metal may interact is proposed. explaining the mechanisms of formation of various braze microstructures and mechanical properties related to them. From the practical point of view, it is proved that induction brazing of compatible samples located in a simple close chamber may be carried out as an effective and inexpensive process.

摘要： The Ge 3d core levels of sub-stoichiometric amorphous germanium-nitrogen (a-GeN) alloys are studied by X-ray photoelectron spectroscopy (XPS). The nitrogen concentration in the samples, as determined from nuclear reaction analysis (NRA), is allowed to vary from zero to approximate to 3 x 10(22) atoms cm(-3). For the whole series of samples both, the chemical shift and the bonding distribution are studied as a function of the nitrogen concentration in the alloys. The chemical shift per Ge-N bond is also investigated using different methods to deconvolute core level energy spectra, and found to be approximately (0.5 +/- 0.1) eV. Furthermore, the present study shows that the Ge-N bond distribution as obtained from the analysis of Ge 3d core level data, is in relatively good agreement with the random bonding model (RBM).

关键词： THIN films   GERMANIUM alloys   NITROGEN   AMORPHOUS substances   RAMAN spectroscopy  

摘要： Thin films of amorphous germanium-nitrogen (alpha-GeN) alloys prepared by the rf sputtering deposition technique have been studied by Raman scattering spectroscopy. The nitrogen content of the samples varies between zero and approximate to 3 x 10(22) atoms cm(-3), as determined from nuclear reaction analysis data. Modifications of the structural characteristics of the Ge-N alloys, probed through their phonon density, were investigated as a function of the nitrogen concentration. In addition to an increase of the network's topological disorder, nitrogen is responsible, at relatively high concentrations, for a structural transition in the alpha-Ge host. The optical and electronic characterization of the samples confirm these changes which are highly dependent on the nitrogen concentration. (C) 1996 American Institute of Physics.

摘要： Thermomechanical properties (stress, thermal expansion coefficient, and elastic modulus) of a-GeNx:H thin films prepared by the rf sputtering technique are reported. Stress measurements are made using a Dektak profilometer to determine the radius of curvature of the film/substrate structure. The majority of the films prepared in this work have compressive stress. A second apparatus based on the deflection of a He-Ne laser beam is used to determine the thermal expansion coefficient and the Young's modulus/(1-Poisson's ratio) by the thermally induced bending method. They depend strongly on the nitrogen concentration.

摘要： A study of the band-gap tailoring of amorphous germanium nitrogen alloys is presented. They have been prepared by the rf reactive sputtering technique, using a c-Ge target in an Ar + NH3 atmosphere. The alloy composition is found to be strongly dependent on the deposition conditions. The optical gap of the material could be tailored from approximately 1.0 to about 3.0 eV by varying the rf power, substrate temperature, nitrogen and hydrogen partial pressures. The rf power, and not the gas composition, is found to be the most important parameter in determining the nitrogen concentration. The hydrogen concentration, on the other hand, has a small influence on the band gap, while the temperature plays an important role on the determination of the alloy structure.