Low Cost Solar Array Project: Composition Measurements by Analytical Photon Catalysis

The applicability of the photon catalysis technique for effecting composition analysis of silicon samples was assessed. Third quarter activities were devoted to the study of impurities in silicon matrices. The evaporation process was shown to be congruent; thus, the spectral analysis of the vapor yields the composition of the bulk sample. Qualitative analysis of metal impurities in silicon was demonstrated e part per million level. Only one atomic spectral interference was noted; however, it is imperative to maintain a leak tight system due to chemical and spectral interferences caused by the presence of even minute amounts of oxygen in the active nitrogen afterglow

Chemical kinetics in an atmospheric pressure helium plasma containing humidity

Atmospheric pressure plasmas are sources of biologically active oxygen and nitrogen species, which makes them potentially suitable for the use as biomedical devices. Here, experiments and simulations are combined to investigate the formation of the key reactive oxygen species, atomic oxygen (O) and hydroxyl radicals (OH), in a radio-frequency driven atmospheric pressure plasma jet operated in humidified helium. Vacuum ultra-violet high-resolution Fourier-transform absorption spectroscopy and ultra-violet broad-band absorption spectroscopy are used to measure absolute densities of O and OH. These densities increase with increasing H 2 O content in the feed gas, and approach saturation values at higher admixtures on the order of 3 × 10 14 cm −3 for OH and 3 × 10 13 cm −3 for O. Experimental results are used to benchmark densities obtained from zero-dimensional plasma chemical kinetics simulations, which reveal the dominant formation pathways. At low humidity content, O is formed from OH + by proton transfer to H 2 O, which also initiates the formation of large cluster ions. At higher humidity content, O is created by reactions between OH radicals, and lost by recombination with OH. OH is produced mainly from H 2 O + by proton transfer to H 2 O and by electron impact dissociation of H 2 O. It is lost by reactions with other OH molecules to form either H 2 O + O or H 2 O 2 . Formation pathways change as a function of humidity content and position in the plasma channel. The understanding of the chemical kinetics of O and OH gained in this work will help in the development of plasma tailoring strategies to optimise their densities in applications

Low cost solar array project composition measurements by analytical photon catalysis. Final report, October 1, 1978-September 30, 1979

The object of this research is to assess the applicability of the photon catalysis technique for effecting composition analysis of silicon samples. In particular, the technique is to be evaluated as a detector for the impurities Al, Cr, Fe, Mn, Ti, V, Mo and Zr. During the first year Al, Cr, Fe, Mn, Ti and Si have been detected with the photon catalysis method. The best fluorescence lines to monitor were established, and initial sensitivites to each of these elements were established by atomic absorption calibration. In the course of these tests vapor pressure curves for these six pure substances have also been mapped. The detection of these impurities in silicon matrices were studied. The evaporation process was shown to be congruent; thus, spectral analysis of the vapor will yield the composition of the bulk sample. Qualitative analysis of metal impurities in silicon was demonstrated below the part per million level. A parametric study for the purpose of establishing optimal running conditions was completed. The parameters varied were temperature, nitrogen and argon pressures, pumping speed, and microwave power. In addition to these mainline tasks much ancillary information was obtained. The emission signatures were determined for several additional elements including As, Bi, B, Ca, Cu, Cr, Ga, Ge Mg, Na, P and Pb. Ionic emission lines for Ca and Mg were determined to be useful for analysis.Many metal hydrides and alkyls were found to be detectable by the active nitrogen technique. As a result of these studies it is concluded that the photon catalysis technique is suitable for bulk analysis of solar grade silicon. (WHK