Ion Bombardment of Single Crystals of Aluminum
The results of bombarding the (100), (110), and (111) surfaces of aluminum single crystals with a narrow beam of 8-kv argon ions are presented. The crystals were tilted at the angles required to bring STA110!, STA100!, STA112!, and STA111! directions parallel to the beam. The experiments were designed to study the effect of incident ion direction on ejection directions and etching rates. Ejection directions as determined from the positions of deposits on hemispherical collectors, were found to be independent of incident ion direction for a given surface orientation. The quantity of material ejected along equivalent ejection directions was observed to decrease as the angle of deviation between the incident ion beam and the ejection direction increased. The principal ejection directions observed were STA110!. Apparent STA116! ejection directions were observed when (110) and (111) surfaces were bombarded. These were caused by an abrupt deflection of momentum from STA110! directions of the crystal to directions close to STA110! of elementary twins. These are formed by surface atoms in twin positions on (111) surfaces developed, in the case of the (110) surface, during bombardment. The STA110! directions of an elementary twin are parallel to certain STA114! directions of the crystal, and, had multilayer twins been formed, the resulting ejection would have been along apparent STA114! directions as a result of Silsbee focusing. Ejection along apparent STA116! directions was not observed from (100) surfaces presumably because predominant STA100! surface grooves produced by bombardment could not contain (111) facets. Under these conditions STA100! ejection was detected. Etching rates, as judged by the occurrence of matte spots, were least when the beam was parallel to the close-packed STA110! directions and greatest when parallel to high index directions making large angles with the STA110! directions. Low etching rates were also observed when the beam became parallel to STA100! and STA112! directions. Any anisotropy in surface migration rates was shown to be negligible in controlling etching rates under the conditions of these experiments.
- Research Organization:
- Dept. of Mines and Technical Surveys, Ottawa
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-037684
- OSTI ID:
- 4659095
- Journal Information:
- Journal of Applied Physics, Vol. 34, Issue 4; Other Information: Orig. Receipt Date: 31-DEC-63; ISSN 0021-8979
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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