Effect of Ge Addition on the Optical Band Gap and Refractive Index of Thermally Evaporated Thin Films

Abstract

The present paper reports the effect of Ge addition on the optical band gap and refractive index of As 2 Se 3 thin films. Thin films of As 2 Se 3 and (As 2 Se 3 ) 90 Ge 10 were prepared by thermal evaporation technique at base pressure 10 −4 Pa. Optical band gap and refractive index were calculated by analyzing the transmission spectrum in the spectral range 400-1500 nm. The optical band gap decreases while the refractive index increases with the addition of Ge to As 2 Se 3 . The decrease of optical band gap has been explained on the basis of density of states; and the increase in refractive index has been explained on the basis increase in disorder in the system.

Optical properties of Ge x As x Se 1-2x glasses

“…Especially the chalcogenide glasses of Ge-As-Se system are characterized by a wide region of glass formation in respect with other ternary compounds, high glass transition temperatures (T g =200÷400 o C), thermal stability, and high refractive index (n=2.4÷2.6) and suitable optical transmission at λ=1.55 μm [6][7][8][9][10]. The chalcogenide glasses Ge-As-Se has a wide region of glass formation in respect with other ternary compounds [1,6].…”