For example, deposition ZnO/Si the Zn2SiO4 phase is appeared at high deposition temperature? What is the effect of Zn2SiO4 phase on lattice constant of ZnO (decreasing or increasing) and why?
The lattice constant will depend on many things like, the phase being formed and the residual stresses in the film. So if there are no residual stresses in your deposited film then the phase formed will have the same lattice constant as the standard phase