what factors affect an epitaxial film's lattice matching and dislocation densities? Are there any possible ways to reduce lattice mismatch and dislocations in various deposition techniques?
For epitaxial growth best substrates are with minimum mismatch e.g. STO for SRO113, TiO2 for CrO2 etc. one of the other ways to reduce mismatch is buffer layer; you grow epitaxially a film on a substrate with higher mismatch, the required film over buffer layer with lower mismatch.
There are various parameters to control the dislocation density including substrate step size, growth rate, substrate temperature
If the film is thin it accommodates its lattice constant to the one of the substrate. The dislocation density is very small but there is strain (in the film and in the substrate). After a critical thickness the film relaxes to its intrinsic lattice constant and dislocations are formed at the interface. The critical thickness depends on the lattice mismatch of the two materials.
In addition to the above indicated suggestions (of suitable substrate and use of buffer layers to minimize lattice mismatch and strain), I suggest the utilization of Molecular Beam Epitaxy (MBE). Epitaxy by MBE guarantees the required characteristics, although it involves expensive vacuum deposition equipment.
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