Abstract
Computer simulations have shown that a nearby surface can engender a significant increase in the number of vacancy defects produced by high-energy displacement cascades in metals of cubic crystal structure. In the present work, the influence of a surface on the production of lattice defects in the bulk by displacement cascades of up to 10 keV in energy in α-Zr has been studied. The basal- or prism-plane surfaces were considered, with the direction of the primary recoil atom making either a high or a low angle to the surface normal. This hcp metal is of interest because self-interstitials migrate preferentially along the basal planes, and so the crystallographic orientation of the surface can influence the final defect state of cascade damage. Surface and subsurface damage increases with increasing energy. The surface damage is much larger for the prism-plane surface. Whereas stable interstitial defects are more readily generated below a basal-plane surface, they are deposited at greater depth below a prism-plane surface. The production of vacancies and interstitials below the surface is contrasted with data for simulations of cascades in the bulk. The results are interpreted in terms of defect properties in Zr and compared with those for cubic metals.