Composition dependence of physical and optical properties in Ge-As-S chalcogenide glasses

• Composition dependence of properties in Ge-As-S glasses is investigated.
• The density is linearly correlated with sulfur content.
• A relation based on molar refractivity is derived to predict the refractive index.
• A method based on diffuse reflectance is proposed to measure the optical bandgap.
• Broad dependence of the optical bandgap on sulfur content is found.

The composition dependence of density (d), refractive index (n) and optical bandgap (Eg) of Ge-As-S chalcogenide glasses is investigated. It is shown that d correlates linearly with sulfur content but relatively poorly with the mean coordination number (MCN). It is also shown that n does not correlate directly with d, and instead a semi-empirical relation based on the molar refractivity (R) of Ge, As and S is derived, permitting to predict n from d with < 1% error. A convenient method based on diffuse reflectance is proposed to measure Eg of Ge-As-S glasses with good accuracy. It is shown that the value of Eg is dominated by the S content. These findings make it convenient to tailor the physical and optical properties of glasses in Ge-As-S system.