Substrate grain orientation

The substrate on which thick films are grown also has to be chosen with care since it influences grain orientation in the film, and particularly mechanical stresses arising because of thermal expansion mismatch. To avoid film cracking the film has to be maintained in compression requiring the substrate thermal expansivity to be greater than that of the PLZT. 

It is noted that the polishing of the polysilicon film will employ the well-known technology of polishing monocrystalline silicon substrates. This gives an opportunity to examine the effect of polycrystallinity and thus of grain boundaries and grain orientation in CMP of Si. Doped vs. undoped polysilicon will also shed... 

Epitaxy is the regularly oriented growth of a crystalline material on a crystalline substrate. The epitaxial layer builds up on the substrate with the same crystallographic orientation, the substrate acting as a seed for the growth. If an amorphous/polycrystalline substrate surface is used, the film will also be amorphous or polycrystalline. Thus, when the substrate is multicrystalline, the growth is also multicrystalline and follows the orientation of the substrate grains. 

Figure 1.13 SAME curves recorded on potentiodynamically formed 20 V Ti02 films on a (0111) oriented Ti substrate grain, (a) A large distance from a laser modified spot (b) close to the modified region (c) on top of the laser modified area ...

Fig. 33. X-ray pole figures of the (108) peak of (a) a seed film prepared by RF plasma evaporation on a MgO single-crystal substrate and (b) a Y123 LPE-grown film. Note that several types of grain orientation exist for the seed film, however the obtained LPE film demonstrates a good crystallinity because formation of inplane aligned island crystallites on the 100 MgO surface is followed by their coalescence and a spiral growth development over the whole surface (Ishida et al. 1997).

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