Increase in nonlinear susceptibility and refractive index in quaternary In15Sb10S15Se60 thin films upon annealing at different temperature for photonic applications

Abstract

The current paper reports the thermal annealing induced amorphous to crystalline transformation of the quaternary In15Sb10S15Se60 thin films prepared by the thermal evaporation method on glass substrate. The prepared films were annealed at 100 °C, 150 °C, 200 °C, and 250 °C under vacuum conditions. The structural characterization was done by X-ray diffraction and Raman spectroscopy which revealed the amorphous to crystalline transformation and the formation of different phases for the annealed films. The composition of the films was verified by Energy dispersive X-ray analysis, whereas the surface morphology pictures were taken by field emission scanning electron microscopy and atomic force microscope. The changes in both linear and nonlinear optical properties of as-prepared and annealed films were studied from UV-Vis spectroscopy data and related empirical formula. The significant reduction in transmission (55–4%) and shifting of absorption edge due to annealing resulted in the decrease of optical bandgap (from 1.641 eV to 1.301 eV) and increase in linear refractive index. The 3rd order nonlinear susceptibility (9.83 ×10−15 to 2.44 ×10−11 esu) and nonlinear refractive index (4.59 ×10−13 to 6.01 ×10−10 esu) were found to be increased due to more polarization effect. The role of annealing temperatures on the variation of different parameters was elaborately explained on the basis of amorphous to crystalline transition and defect states in the localized region. Based on the observed changes in the linear and nonlinear optical parameters by thermal annealing, the In15Sb10S15Se60 thin films could be a suitable candidate for numerous photonic and optoelectronic applications.