The Growth of Single Crystal Films of Silver on Rocksalt by Sputtering

Thin films of silver on rocksalt have been prepared by diode sputtering in an argon discharge. Deposition rate, substrate temperature, and film thickness have been varied, and dependence of orientation on these parameters has been studied. Within a deposition rate range of 0.1 to 1.15 angstrom/sec, films have been grown with (100) [110](Ag) // (100) [110](Nacl) orientation, at temperatures in the range - 35 to 0 degrees C. Higher rates required higher temperatures. Films giving these results were all 200 angstrom in thickness. A thickness dependence of orientation has been observed for films below 120 angstrom in thickness. The above results are discussed in terms of the effect of arrival energy of the sputtered material at the substrate. The results of calculations, on the effect of gas pressure on the arrival energy, are presented and it is shown that, at 10(-2) torr, up to 15% of the arriving atoms will have energies above 0.6 eV. That the observed rate, temperature, and thickness dependence of epitaxy are due to surface cleaning and penetration effects caused by the energy of arrival of the atoms is shown to be possible. The effect of charged particle bombardment of the substrate is also considered. It is shown that this may also be an important parameter affecting the growth.