Growth Mechanisms and Characterization of Hydrogenated Amorphous-Silicon-Alloy Films, Annual Subcontract Report, 14 February 1992 - 13 February 1993
This report describes work performed to better understand the atomic-scale structure of glow-discharge-produced a-Si:H, a Ge:H, and a-Si:Ge:H films; its effect on film quality; and its dependence on deposition discharge conditions. Hydrogenated a- Si films are deposited from a silane rf discharge onto atomically flat crystal Si and GaAs substrates. The substrates are then transferred in vacuum to a scanning tunneling microscope, where the atomic-scale surface morphology is measured. The films were deposited at T{sub s} = 30{degree}C and 250{degree}C from a silane rf glow discharge using device-quality deposition conditions of 2.66 Pa (0.5 Torr) silane pressure, 1.7 {Angstrom}/s deposition rate, and small power/flow; IR absorption, {sigma}{sub L}, and {sigma}{sub D} indicate high-quality intrinsic films. From the thickness dependence of the surface morphology, we determined that the films initially conform smoothly to an atomically flat Si or GaAs substrate, but as the thickness increases the roughness steadily increases to approximately 10% of the length of the scanned region. The surface of 100-400-nm-thick films is highly inhomogeneous, with steep hills and canyons in some areas and large atomically smooth regions in others. These unexpectedly large surface irregularities indicate severe and often connected void structures in the growing film, as well as relatively limited-range surface diffusion of the incorporating SiH{sub 3} radicals. On the other hand, large areas of atomically flat surface were occasionally found, indicating the possibility of growing a homogeneous and compact amorphous film if appropriate growth conditions could be discovered.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 10181927
- Report Number(s):
- NREL/TP-411-5749; ON: DE93018202
- Resource Relation:
- Other Information: PBD: Aug 1993
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SILICON SOLAR CELLS
FABRICATION
SILICON
CRYSTAL GROWTH
PROGRESS REPORT
AMORPHOUS STATE
FILMS
PHOTOVOLTAIC CONVERSION
GERMANIUM
SUBSTRATES
GALLIUM ARSENIDES
DEPOSITION
GLOW DISCHARGES
SILANES
photovoltaics
solar cells
amorphous silicon
alloy
growth
characterization
film
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360601
PREPARATION AND MANUFACTURE