40 MeV ~(28)Si~(5+) ion induced blue shift in the optical band gap of amorphous Se_(80-x)Te_(20)Pb_x thin films

摘要

Amorphous thin films of Se_(80-x)Te_(20)Pb_x(0 < x < 2) have been prepared by thermal evaporation method. The effect of 40 MeV ~(28)Si~(5+) ion irradiation on the optical band gap (E_g) has been investigated. Blue shift in the optical band gap of Se_(80-x)Te_(20)Pb_x(0 < x < 2) has been observed upon irradiation with heavy ions. The E_g of Se_(80-x)Te_(20)Pb_x (x = 1.4) increases from 1.36 to 1.48 eV with the increase in the irradiation fluence from 10~(12) to 5 x 10~(13) ions/cm~2, respectively. All the other samples also show similar behavior. Results have been explained, considering strong electron-lattice coupling and some changes in the defects configurations upon irradiation with heavy ions, resulting in an increase of the optical band gap.