Techniques for measuring the composition of hydrogenated amorphous silicon–germanium alloys (original) (raw)
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SIMS characterization of amorphous silicon germanium alloys grown by hot-wire deposition
AIP Conference Proceedings, 1999
In this paper, we present methods for the quantitative secondary ion mass spectrometry (SIMS) characterization of amorphous SiGe :H alloy materials. A set of samples was grown with germanium content ranging from 5% to 77% and was subsequently analyzed by electron probe X-ray microanalysis (EPMA) and nuclear reaction analysis (NRA). Calibration of the SIMS quantification was performed with respect to EPMA data for germanium and NRA data for hydrogen.
Seventh E.C. Photovoltaic Solar Energy Conference, 1987
Si-SI and Si-A (A being C, N, Ge) bond lengths have been determined as a function of composition. The Si-C distance was found to vary significantly, while the Si-Ge and SiN distances remain almost constant. A high frequency signal has been detected in the a-SiI-,C, :H and a-SiN, :H films at large x due to a second shell contribution. The compositions of the first coordination shell are also reportedand discussed in terms of different local coordination models. The study of semiconducting binary alloys is of great interest from the fundamental as well as applied point of-view. This is even more true for the hydrogenated amorphous alloys based on a-Si due to the flexibility of the deposition processes, 8.g. glow discharge, and an apparent continuous miscibility of the elements. This seems to be the case also for silicon-carbon and silicon-nitrogen that in the crystalline phase form a definite compound and are not miscible. Up to now no direct structural measurements have been reported on a-Sil-,Cx:II and a-SiNx:H while a-Si,xGex:H bas been already studied at the Ge K-edge [1,21.
Thermal desorption spectrometry study of Si1−xGex:H amorphous alloys
Applied Surface Science, 1997
A thermal desorption spectrometry study of hydrogen from silicon germanium alloys is presented. Amorphous Si 1 _xGex:H (0 < x < 1) thin films were prepared by ion beam assisted evaporation on a substrate maintained at 120°C. Infrared spectrometry experiments showed that these alloys essentially contain silicon and germanium dihydride sites. Effusion experiments allowed us to deduce the Gibbs free energy of hydrogen desorption from the Sill and GeH sites as a function of the germanium content.
1994
We analyzed the physical properties of hydrogenated amorphous silicon (a-Si:H) samples grown by plasma enhanced chemical vapor deposition, by means of infrared spectroscopy, mass-density, and optical measurements. We applied the usual infrared spectroscopic techniques to evaluate the amount of incorporated hydrogen and to investigate the in8uence of the Si-H bonding con6gurations on the optical and electronic properties of a-Si:H obtained by this widely used deposition process, and with parameters so chosen as to obtain 61ms having state of the art characteristics. We carried out an exhaustive study of the difFerent infrared absorption peaks, generally ascribed to different bonding con6gurations of H in Si, with a view to distinguishing the difFerent contributions of SiH, SiHz, (SiHs)" to the spectral response of the material and to relating them to deposition temperature. The correlation of this infrared spectral analysis with mass-density measurements has evidenced that, for hydrogen content below 10 at. %, isolated SiH and SiHq bonds occur, whereas, with higher hydrogen concentrations, the formation of (SiH&)"chains gives rise to empty cavities where hydrogen is preferentially incorporated. In addition, optical measurements show that samples deposited at temperatures below 170'C exhibit energy gaps and defect densities, which are quite difFerent to those expected if only the effects of SiH groups are considered.
Journal of Non-crystalline Solids, 2006
Very good electronic properties of hot-wire CVD a-Si,Ge:H alloys have been established by junction capacitance methods. The samples were deposited using a tantalum filament maintained at about 1800°C instead of the usual 2000°C tungsten filament process. Urbach energies below 45 meV were found, as well as annealed defect densities below 10 16 cm À3 , for Ge fractions up to 30 at.%. However, samples with 10 19 cm À3 levels of oxygen exhibited much broader Urbach energies and higher defect densities. Light induced degradation was examined in detail for one a-Si,Ge:H alloy sample and compared to the behavior of PECVD grown a-Si:H alloys of similar optical gap.
Solar Cells
The use of nuclear reactions to determine the concentration of hydrogen in thin films is reviewed with particular emphasis on the analysis of thin film amorphous silicon (a-Si). The 15N hydrogen profiling technique which can be used to measure quantitatively the hydrogen concentration versus depth in any solid is described in detail. This method has good sensitivity (less than 100 ppm} and good depth resolution (about 4 nm near the surface) and can measure hydrogen concentration to depths of several microns. Although this hydrogen analysis technique is rather new, it has already been widely applied in the analysis of the hydrogen content and densities of thin film a-Si. The results of these measurements are summarized and discussed in relationship to the results of other analytic techniques.
1998
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or nprescnts that its use would not infringe privately owned rights. Reference herein to any spccific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise docs not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Preparation of Hydrogenated Amorphous Silicon by Homogeneous Chemical Vapor Deposition
1994
2014 Ce papier décrit une nouvelle méthode pour obtenir des alliages amorphes semiconducteurs hydrogénés. La méthode que nous utilisons est l'évaporation réactive. Les alliages silicium-étain sont préparés par coévaporation dans une atmosphère d'hydrogène atomique. Nous discutons l'influence des différents paramètres de préparation (pression partielle d'hydrogène, température du tube de tungstène, température du substrat, recuit...) sur les propriétés électriques des échantillons.
Microstructural and Vibrational Characterization of the Hydrogenated Amorphous Silicon Powders
MRS Proceedings, 1993
Hydrogenated nanophase silicon powders prepared by low pressure and low temperature rf plasma using pure silane gas, have been characterized by transmission electron microscopy (TEM), Fourier transform IR spectroscopy (FTIR) and thermal desorption spectrometry (TDS) of hydrogen. By means of these analysis, the evolution of the hydrogen bonds and the oxidation processes as a consequence of annealing of the silicon powders under vacuum or atmospheric conditions have been investigated. The TDS results reveal the fundamental differences between the concentrations of hydrogen weakly and strongly bonded in silicon powders as compared to amorphous silicon films, and the FTIR spectra evidence the oxidation process taking place in the silicon powders as a consequence of the annealing. These results along with the TEM analysis show that silicon powder particles present intergrain linkage. We also study the silicon powder particles considering their microstructure and vibrational characteristi...
Hydrogen in amorphous and microcrystalline silicon films prepared by hydrogen dilution
Journal of applied …, 1996
Hydrogen incorporation in silicon layers prepared by plasma-enhanced chemical-vapor deposition using silane dilution by hydrogen has been studied by infrared spectroscopy ͑IR͒ and elastic recoil detection analysis ͑ERDA͒. The large range of silane dilution investigated can be divided into an amorphous and a microcrystalline zone. These two zones are separated by a narrow transition zone at a dilution level of 7.5%; here, the structure of the material cannot be clearly identified. The films in/near the amorphous/microcrystalline transition zone show a considerably enhanced hydrogen incorporation. Moreover, comparison of IR and ERDA and film stress measurements suggests that these layers contain a substantial amount of molecular hydrogen probably trapped in microvoids. In this particular case the determination of the total H content by IR spectroscopy leads to substantial errors. At silane concentrations below 6%, the hydrogen content decreases sharply and the material becomes progressively microcrystalline. The features observed in the IR-absorption modes can be clearly assigned to mono-and/or dihydride bonds on ͑100͒ and ͑111͒ surfaces in silicon crystallites. The measurements presented here constitute a further indication for the validity of the proportionality constant of Shanks et al. ͓Phys. Status Solidi B 110, 43 ͑1980͔͒, generally used to estimate the hydrogen content in ''conventional'' amorphous silicon films from IR spectroscopy; additionally, they indicate that this proportionality constant is also valid for the microcrystalline samples.