On the properties and stability of thermally evaporated Ge-As-Se thin films
Date
2009
Authors
Bulla, Douglas
Wang, Rongping
Prasad, Amrita
Rode, Andrei V
Madden, Steve
Luther-Davies, Barry
Journal Title
Journal ISSN
Volume Title
Publisher
Springer
Abstract
Thin films of Ge-As-Se chalcogenide glasses have been deposited by thermal evaporation from bulk material and submitted to thermal treatments. The linear refractive index and optical band-gap for as-deposited and annealed films have been analyzed as function of the deposition parameters, chemical composition and mean coordination number (MCN). The chemical composition of the films was found to be directly affected by deposition rate, with low rates producing films with elevated Ge and reduced As content, whilst at high rates the Ge content was generally reduced and As levels increased compared with the bulk starting material. As a result films with close to the same stoichiometry as the bulk glass could be obtained by choosing appropriate deposition conditions. As-deposited films with MCN in between 2.44 and 2.55 showed refractive indices and optical band-gaps very close to those of the bulk glass whereas outside this range the film indices were higher and the optical gaps lower than those of the bulk glass. Upon annealing at close to their glass transition temperature, high MCN films evolved such that their indices and band-gaps approached the bulk glass values whereas at low MCN films resulted in no changes to the film properties.
Description
Keywords
Keywords: Annealed films; As content; As-deposited films; Band gaps; Bulk glass; Bulk materials; Chalcogenide glass; Chemical compositions; Deposition conditions; Deposition Parameters; Film indices; Film properties; Ge content; Glass transition temperature; High r
Citation
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Source
Applied Physics A: Materials Science and Processing
Type
Journal article