Formation of Stacking Faults in Single-Crystal Films of Copper Grown on NaCl, KCl, and LiF Substrates

Abstract

Copper films 700 Å thick deposited on NaCl or KCl at 330°C are preferentially oriented on the (001) plane, and after heating at 630°C they exhibit complex stacking faults of 2 to 3 μ in width. Examination of carbon replicas and of platinum-shadowed copper films shows that straight surface terraces of 50 to 100 Å in elevation occur over the faults and that these terraces are formed in the copper film while on the substrate. Copper deposited on cleaved LiF substrates shows several orientations, and annealing up to 745°C produces no preferential growth among them; no stacking faults appear in the annealed film. On the LiF preheated above 700°C before cleaving, copper films are deposited as single crystals and when annealed at 745°C show complex stacking faults and terraces as observed with the chloride substrates. In all cases the faults are believed to form under compressive stresses in the single crystal of copper as the film on the substrate is cooled from a high temperature.