Shock crystallization in amorphous films of dielectrics

Abstract The circular, ring-shaped crystallization called shock crystallization was observed in amorphous films of silica and silicon oxynitride heated up to 1150°C. The crystallization rate is several orders of magnitude higher than that of ususal crystallization processes. The microstructure of the regions of shock crystallization in silica films is characterized by radial growth of crystallites from the center, i.e. the starting point of phase transition, or by alternation of the regions of radial growth and concentrically located regions that partially retain an amorphous structure. Silicon oxynitride films show a ring-shaped locus of colonies of crystalline separations with respect to the center. A model of shock crystallization was developed on the basis of both experimental results and literature data. A calculation was made of the dependence of the relative width of neighbouring crystallizing regions on the reduced energy of internal stresses in amorphous and crystallizing regions of the film and on the relation between an activation energy of crystallization and crystallization heat. The crystallization rate was estimated. The calculated values of the relation of the ring sizes at the initial stage and before cessation of shock crystallization. The possible causes of the difference in morphology of crystallizing regions silica and silicon oxynitride are discussed.