For the first time a face-centred-cubic metal film has been epitaxially grown on sapphire. Film crystallinity and ion-etch characteristics were studied using back reflection X-ray diffraction and scanning electron microscope techniques. Single-crystal copper films have been deposited on basal plane sapphire substrates in the temperature range 240 to 375° C. The films exhibited bulk metal resistivity. Ion-etching studies of the films, using argon ions, have demonstrated superior quality, resolution and vertical etch profile of interconnection transmission lines over those of polycrystalline or less crystalline films. © 1970 Chapman and Hall Ltd.