Crystal Orientations and Film Surface Morphology

Besides crystal orientation and surface morphology, the termination of the ZnO crystallites is another important parameter for the optimization of ZnO films High piezo-electric coupling coefficients can only be achieved if the ZnO crystallites have a uniform polarity. There are only a few processes that allow the polarity of the ZnO films to be assessed. 

Based on this mechanism. Wild et al.l l developed a two-dimensional computer program to simulate the crystal growth evolution and the surface morphology of polyerystalline films grown from square nuclei with random orientations and random positions on a substrate. The calculated - - and experimentalP lP l results show that, for the diamond films (150-400 pm in thickness) investigated under the experimental conditions, (110) is the direction of fastest growth with the film surfaee eonsisting of 111 planes. 

In addition to the statistical nature of the interface instabilities active in diamond CVD, the orientation effect and anisotropic growth of crystals (i.e., evolutionary selection) play an important role in the observed instability phenomenon. Surface chemical reactions that occur preferentially between the growing diamond surface and oxidizing species in the combustion synthesis ambient also influence the development of the microstructure and morphology of crystals in diamond films. For example, in combustion CVD,... 

Grain boundaries are internal interfaces and behave much like external surfaces, but now we have to be concerned with two crystal orientations, not one. Just as for surfaces, we have a pressure difference associated with the GB curvature and a driving force that tends to lead to an overall increase in grain size whenever possible. Grain morphology and GB topology are two aspects of the same topic. It is instructive to think of the model of soap foams a soap film is flat when in equilibrium and it has a finite thickness. Three soap films meet along a line—a TJ. If you blow on a soap film (apply a pressure) it bows out until the surface tension balances the applied pressure. 

---