High-energy ion treatments of amorphous As40Se60 thin films for optical applications

The treatment of 100 MeV Ag swift-heavy ion (SHI) irradiation with rive different fluences (3 x 10(10), 1 x 10(11), 3 x 10(11), 1 x 10(12), and 3 x 10(12) ions/cm(2)) was used to design optical and structural properties of amorphous (a-) As40Se60 chalcogenide thin films. Swanepoel method was applied on transtnission tneasuretnents to determine the changes in optical bandgap. Tauc parameter and linear optical paratneters, i.e., linear optical absorption, extinction coefficient and linear refractive index. Dispersion of the material was determined by Wemple DiDomenico relation. Changes in nonlinear optical parameters of third-order optical susceptibility and nonlinear refractive index were determined using semi-empirical relations. Changes in surface morphology of the films were investigated using SEM observation, which indicated that fluence 3 x 10(12) ions/cm(2) was upper threshold limit for these films for ion treatment. It is observed that optical bandgap reduces from 1.76 eV to 1.64 eV, and nonlinear refractive index increases from 1.31 x 10(-10) [esu] to 1.74 x 10(-10) [esu]. Linear refractive index initially increases from 2.80 to 3.52 (for fluence 3 x 10(10) ions/cm(2)) and then keeps decreasing. The observed changes in optical properties upon irradiation were explained in terms of structural rearrangements by Raman measurement. The study was compiled with the previous literature to propose SHI as an effective optical engineering technique to achieve desired changes according to the need of optical/photonic applications. (c) 2014 Chinese Materials Research Society. Production and hosting by Elsevier BA'. All rights reserved.