Optical and spectroscopic characterization of germanium selenide glass films

2009

A previews study of germanium selenide glass films by Scanning Electron Microscopy and Atomic Force Microscopy (AFM) revealed a heterogeneous surface morphology consisting of granular regions ~ 15-50 nm in size, which cause high optical losses. The present work was performed in order to further characterize such materials using spectroscopic ellipsometry, infrared and Raman spectroscopies. Chalcogenide glass films with GeSe2, Ge28Sb12Se60 and GeSe compositions have been deposited on single crystal silicon and silica glass substrates by vacuum thermal evaporation. The film thickness and the optical constants were obtained from spectroscopic ellipsometry using the Tauc-Lorenz dispersion formula. A model was derived for the film structure, which included a roughness layer at the surface. This top layer was found to have a thickness of ~ 5 15 nm, of the order of the size of the granular regions previously reported. The optical bandgap of the samples increased with increasing selenium content, while the refractive index decreased. Despite a previous report of large scale phase separation in bulk Ge26Sb14Se60 glass, the fundamental IR and Raman spectra obtained in the present work did not provide any clear evidence for such phase separation which could be associated with the heterogeneous nanostructure observed at the surface of the films.

Autores da comunidade :

• 

  L

  Luís Filipe da Silva dos Santos

  ist12589

  Afiliações e fontes

  IST > ICEMS

  Instituto de Ciência e Engenharia de Materiais e Superfícies

  IST > DEMat

  Departamento de Engenharia de Materiais

• 

  R

  Rui Manuel Amaral de Almeida

  ist11323

  Afiliações e fontes

  IST > ICEMS

  Instituto de Ciência e Engenharia de Materiais e Superfícies

  IST > DEQ

  Departamento de Engenharia Química

J. Non-Crystalline Solids

1984

1988

355

37-42

materials-engineering - Engenharia dos Materiais

eng - Inglês