Stability of microdefects in poly-Si films grown by α-Si solid state crystallization

For poly-Si thin film transistors (TFTs) in order to improve the electrical characteristics of the poly-Si films a better understanding of the structure of the films and the related defects versus grain size is needed. In this contribution the structure and the stability of defects of the α-Si films which are formed by low temperature solid state crystallization and subsequent annealing is discussed. Amorphous silicon films were deposited on glass by the LPCVD and annealed at 610°C for 8 h. Most of the crystallites exhibit a three dimensional ellipsoidal shape. The large axis of the ellipsoid coincides with the ⟨112⟩ crystallographic direction while the smallest one is along the ⟨111⟩ direction. In the core of the crystallites multiple (111) type twins are formed along the ⟨112⟩ direction