Abstract: This invention is directed toward methods for fabricating polycrystalline thin films. More particularly, the invention is directed toward optimized solid phase crystallization of plasma enhanced chemical vapor deposited amorphous silicon thin films as a means for obtaining, with a low thermal budget, polycrystalline silicon thin films comprising larger grain sizes and smother surfaces. The process of plasma enhanced chemical vapor deposition is quantified for silane containing various types of dilutants, thereby allowing deposition temperature, type of dilutant, type of plasma and other parameters to be controlled to yield the desired crystallization grain size at the desired thermal budget. Methods of annealing, annealing temperature, and pre-annealment treatments are also quantified such that grain size and thermal budget can be controlled in the fabrication of polycrystalline silicon thin films.