High‐Temperature Healing of Cracklike Flaws in Titanium Ion‐Implanted Sapphire

Controlled‐geometry voids were introduced into unim‐planted and Ti‐implanted high‐purity c ‐axis sapphire substrates using microfabrication techniques and ion beam etching, and subsequently transferred to an internal interface by hot‐pressing. The morphological evolution of crack‐like and channellike defects oriented parallel to the basal plane in response to anneals at 1700°C was studied. The healing behavior of defects in the unimplanted and Ti‐ion‐implanted samples differs significantly. Ti additions appear to reverse the directional dependence of the healing characteristics in undoped sapphire, greatly stabilizing defects with edges aligned along the [1100] direction, while reducing the stability of defects with edges aligned parallel to the [1120] direction relative to unimplanted sapphire. The healing characteristics of unimplanted and Ti‐implanted sapphire substrates are compared and contrasted with those observed previously in Ca‐ and Mg‐ion‐implanted sapphire.