An electron diffraction study of oriented crystal growth in gold and copper films condensed in vacuum at oblique vapour incidence

Abstract

Gold and copper films were condensed from a small source (at 30 and 20 AA s-1 where i=0) over a range of angles of incidence i from 0 to >45 degrees , in vacuum at defined pressures between 1*10-8 and 2*10-3 Torr, on flat glass and polished stainless steel substrates at room temperature. After the initial very thin random layer, growth developed in (111) orientation with its axis tilted by delta towards the vapour stream, and delta rose quickly from approximately 0 as deposition proceeded, at 5*10-6 Torr or lower becoming nearly constant at 4-6 degrees when i=45 degrees , for films >300 AA thick. There was little or no change in delta when additional (111) twinning occurred. When the later growth in (211) orientation was developed, delta immediately increased by about 20 degrees , to delta approximately 25 degrees , indicating its origin by (211) face development rather than by secondary (111) twinning which would have increased delta by only about 5 degrees . Observations at oblique vapour incidence are clearly important in establishing the origin of preferred orientations arising as films grow thicker. The relation delta approximately=ki leads to expressions of form K exp (-n phi 2/2) for the film-surface distribution function f( phi ) for the (111) oriented gold, with n/2=3.25 for films at 1*10-8 Torr, and n/2=7 for films at 5*10-4 and 2*10-3 Torr.