Efficient solar cells by space processing. Final report, October 1, 1978-December 14, 1979
Thin films of electron beam evaporated silicon were deposited on molybdenum, tantalum, tungsten and molybdenum disilicide under ultrahigh vacuum conditions. Mass spectra from a quadrapole residual gas analyzer were used to determine the partial pressure of 13 residual gases during each processing step. Surface contamination and interdiffusion were monitored by in-situ Auger electron spectrometry. The substrates were characterized by x-ray analysis and SEM in the topographical and electron diffraction mode. It was found that on polycrystalline tungsten with a (100) orientation, silicon was grown with a grain size measuring 3000 A in cross section and with (110) orientation below 630/sup 0/C. At 670/sup 0/C, silicon grains had grown to one micron in cross section and these grains had (111) and (110) orientations. On polycrystalline molybdenum substrates with (100) orientation, silicon grains measuring 2000 A across grew with a (110) orientation as high as 670/sup 0/C. The presence of phosphorus in the silicon was responsible for attaining these elevated temperatures with silicide formations. Heteroepitaxial silicon was grown on polycrystalline MoSi/sub 2/ at 800/sup 0/C. The silicon grew on (111) MoSi/sub 2/ grains. This growth was sensitive to the presence of oxygen during deposition, the rate and length of deposition as well as the substrate orientation. Above 950/sup 0/C silicon growth was no longer heteroepitaxial but crystals 80 ..mu..m in cross section were obtained. The presence of oxygen at a partial pressure of 1 x 10/sup -10/ torr was found to reduce the size of silicon grains at 1100/sup 0/C.
- Research Organization:
- Ames Lab., IA (USA)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5287304
- Report Number(s):
- IS-4723
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
36 MATERIALS SCIENCE
360601 -- Other Materials-- Preparation & Manufacture
AUGER ELECTRON SPECTROSCOPY
CONTAMINATION
CRYSTAL STRUCTURE
CRYSTALS
DEPOSITION
DIRECT ENERGY CONVERTERS
ELECTRON SPECTROSCOPY
ELEMENTS
EPITAXY
EQUIPMENT
EVAPORATION
FABRICATION
GAS ANALYSIS
GRAIN SIZE
MASS SPECTROSCOPY
METALS
MICROSTRUCTURE
MOLYBDENUM
MOLYBDENUM COMPOUNDS
MOLYBDENUM SILICIDES
NONMETALS
PHASE TRANSFORMATIONS
PHOSPHORUS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
POLYCRYSTALS
REFRACTORY METALS
SCHOTTKY BARRIER DIODES
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
SEMIMETALS
SILICIDES
SILICON
SILICON COMPOUNDS
SILICON SOLAR CELLS
SIZE
SOLAR CELLS
SOLAR EQUIPMENT
SPECTROSCOPY
SUBSTRATES
SURFACE COATING
TANTALUM
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TUNGSTEN
VACUUM COATING