Bulk glasses with the chemical composition Ge_y Se_94−yIn₆ (8 ⩽ y ⩽ 30 at%) have been prepared from high purity constituent elements. Fragments of the bulk glasses are used to deposit thin films by vacuum thermal evaporation. The optical band gaps (E_g s) of the as-deposited films have been measured. The allowed optical transition is found to be indirect. The relation of E_g to the covalent coordination number, Z, is demonstrated by varying the composition parameter y of the thin films. A maximum in the compositional dependence of E_g is attained at Z = 2.63. The cohesive energies (CE) of the investigated samples have also been calculated using the method suggested by the chemical bond approach. It is found that the composition dependence of the CE also possesses a peak at Z = 2.63.A plausible explanation based on the bonding considerations between the constituents has been provided for the understanding of the E_g-Z and CE-Z dependences for these Ge–Se–In thin films.
PACS 61.43.Dq;78.66.Jg

Title

Optical Materials, Volume 29, Issue 9, May 2007, Pages 1143-1147

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Publisher Country

Palestine

Publication Type

Both (Printed and Online)

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Year

2007

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