CRYSTALLIZATION STUDY OF GLASSY TE-SE-I THIN-FILMS

We studied the thermally induced amorphous-to-crystalline transformation in RF sputtered Te-Se-I films with an approximately constant Te: Se ratio of 3:4 and with different halogen concentrations in the range 0-20 at% I. Crystallization usually occurred via the formation and growth of cylindrites (two-dimensional, radially aligned polycrystalline aggregates) which exhibited a branched fibrillar morphology. The major effects of the halogen on the transformation were as follows: (i) The halogen strongly stabilized the amorphous phase. Crystallization took place when there was substantial superheating at temperatures above 80-degrees-C after the halogen was depleted. (ii) The halogen restricted the cylindrite formation to a thin surface layer and dictated the details of the branched morphology. (iii) In the halogenated films all the cylindrites appeared suddenly rather than nucleating at a constant rate and their density was reduced by a factor of 100.