ROLE OF LONE-PAIR ELECTRONS IN REVERSIBLE PHOTOSTRUCTURAL CHANGES IN AMORPHOUS CHALCOGENIDES

Results of in-situ X-ray absorption fine structure and Raman scatterin g measurements of photostructural change in amorphous selenium and bin ary As,Se, glass are reported. It is demonstrated that in the photoexc ited state the coordination number of selenium species increases rever sibly. This increase is caused by the formation of dynamic interchain (interlayer) bonds via interaction of excited electrons of lone-pair o rbitals whose presence is essential for the process to occur. After su bsequent bond breaking a transition to a metastable state takes place. (C) 1998 Elsevier Science B.V. All rights reserved.