Investigations on the growth and morphology of TiO2 in the TiO2-Na2B4O7 system with and without impurities using a new LPE method

Liquid phase epitaxy (LPE) growth mechanisms and the effects of impurities were investigated using a new method. It was demonstrated that the Volmer-W eber mechanism operates on (00 1), a K face according to the Hartman-Perdok theory, whereas the Frank-van der Merve mechanism operates on (110), an F face, and on (1 1 1), an S face. It was also confirmed that tri-valent cati ons with ionic radii close to Ti4+ ions transform the character of the (1 1 1) face from an S face to a K face, producing a greatly accelerated growth rate in the c-axis direction, whereas the same impure ions reduce the grow th rate on the (110) face. This difference is well represented in the chang e of the surface morphologies of the respective faces. The observed morphol ogical changes are interpreted on the assumption that oxygen ions around Ti 4+ ions are destabilized by the adsorption of tri-valent cations. leading t o breaking the PBC in the (I 1 1) face. (C) 2001 Elsevier Science B.V. All rights reserved.