Metastable, drawing-induced crystallization in As2Se3 fibers

Pulsed As-75 nuclear quadrupole resonance (NQR) experiments performed on rapidly-drawn (> 100 m/min) fibers of As2Se3 reveal structure which differs from the bulk, well-annealed glass. In addition to the presence of As-As bonds in the nominally stoichiometric fibers, a distorted 'crystalline' phase occurs at the greatest draw rates. Like the Ge-Se-S system, this phase probably involves more ordered local molecular clusters whose sizes are not yet well-determined. Because these crystalline regions are highly distorted compared to bulk, crystalline As,Se,, they are not observable by X-ray spectroscopy except in a few cases. On the other hand, the NQR experiments show the presence of crystalline regions. In all cases, the crystalline phase makes up less than 5% of the volume. In addition to being strained, the imbedded crystallites partially 'anneal' to the amorphous phase over time when stored at 300 K. This annealing behavior is similar to that which exists in the Ge-Se-S system, but different from the 'photo-induced amorphization' recently reported for evaporated AsSe films. (C) 1998 Elsevier Science B.V. All rights reserved.