Crystal growth and orientations in vacuum-condensed aluminium, and their dependence on residual air pressure and film thickness

Electron diffraction at grazing incidence shows the nature of the crystal growth and orientations in Al films condensed at similar 30 Å s −1 on glass and polished stainless steel initially at room temperature, as a function of film thickness H and residual air pressure p . The same sequence of orientations is found at all p from 5 × 10 −8 to 2 × 10 −3 Torr - random-polycrystalline up to H similar 1000 Å at 5 × 10 −8 Torr, decreasing to similar 300 Å at 10 −3 Torr. The Al crystals have then developed {111} faces and grow preferentially with a {111} face parallel to the substrate or nearly so, until in still higher strata of further growth octahedral twinning leads to some {511} orientation, and then secondary twinning together with presence of {311} faces leads to {311}. For the stage of onset of each orientation, H is a function of p , and thus of the degree of chemisorption of oxygen on the growing faces. Results at 6-9 Å s −1 are similar. {100} faces and orientation arise if a high proportion of water vapour is present.