Preparation of As–In–S:Sm thin films and a study of their properties

Abstract

The study examines the physico-chemical properties of thin films of the As–In–S:Sm system. Thin amorphous films were prepared by thermal evaporation (TE) from two sources (As–In–S glass and metallic Sm) and by pulsed laser deposition (PLD). The films prepared with PLD contained more Sm and In than the TE films. The optical gap of the PLD films is lower than that of the TE films (Egopt=2.29eV for TE, Egopt=1.88eV for PLD), both are dependent on exposure of films and on their annealing. The as-deposited PLD films did not contain any separated As4S4 molecules; overstoichiometric arsenic was incorporated into the amorphous matrix. The index of refraction of the prepared PLD films (nћω→0=2.48) is higher than that of the TE films (nћω→0=2.35). The corresponding coefficient of the third order non-linear optical susceptibility (χ(3)) is also higher (PLD: 6.83×10−20m2/V2, TE: 4.02×10−20m2/V2). The structural changes induced by exposure and by annealing, determined by Raman spectroscopy, can be described through photochemical reactions (induced by exposure) and chemical reactions (induced by annealing). The strong luminescence bands were assigned to inner f–f electron transitions. The material is promising for a number of applications.