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

Abstract

Controlled-geometry voids were introduced into unimplanted 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 cracklike 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-ionimplanted 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 [IT001 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.

High‐Temperature Morphological Evolution of Lithographically Introduced Cavities in Silicon Carbide

“…Figure 3 shows a set of such features, etched into a silicon-terminated face with the 1000 µm edge oriented perpendicular to <1210 >, after 128 h at 1900°C. Geometrically similar features, when introduced into the basal plane of sapphire develop periodic undulations that appear to be sinusoidal at similar magnifications, and channels break up by Rayleigh instabilities [6][7][8][9]. In the present case, the evolution is dominated by edge facetting.…”

“…The exposure pattern is dictated by the pattern of features in a mask; two different masks were used in the present work. The mask patterns have been described elsewhere [7,19]. The exposed positive photoresist can be selectively removed with a developer (Microposit Developer Concentrate, Shipley Inc., Marlborough, ma).…”

“…Prior work has focussed on model studies of surface properties in doped and undoped sapphire. The effects of dopants and crystal orientation on crack healing [5][6][7] and on Rayleigh instabilities [6][7][8][9] as well as the effects of dopants and temperature on relative surface energies (the Wulff shape [10,11]) have been reported in the literature.…”

Surface-energy-anisotropy-induced orientation effects on Rayleigh instabilities in sapphire

“…However, it is not the variation in surface energy per se that matters, but the second derivative of the surface energy with orientation that is critical in dictating the perturbation energetics and kinetically dominant wavelengths [7]. Local [9][10][11][12], and on quantifying the effects of SEA on the morphological evolution of internal voids [9,[13][14][15][16][17][18][19][20][21][22][23][24][25] Glaeser [31] extended the analysis of Stölken and Glaeser [29] [32][33][34][35] to studies in which the equilibrium shape of both undoped and doped sapphire have been determined as a function of temperature [9-12, 22, 36].…”

Mechanisms of microstructure development at metallic-interlayer/ceramic interfaces during liquid-film-assisted bonding

“…The breakup of microlithographically processed pore channels in -24-sapphire and silicon carbide have been studied extensively. 10,[96][97][98][99][100][101][102] The effects of crystallographic orientation, surface energy anisotropy, perturbation amplitude and wavelength, impurity content, and temperature on the breakup of the pore channels were all areas of interest in the various studies. The transition from diffusion-controlled evolution kinetics to surface-attachment and nucleation-limited kinetics has proven to cause difficulties when using these studies to extract diffusivity information.…”