Stoichiometric dependent optical limiting in PLD SiOx thin films

Department of Physics, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India

Adv. Mater. Lett., 2017, 8 (4), pp 331-335

DOI: 10.5185/amlett.2017.6931

Publication Date (Web): Mar 14, 2017

Copyright © IAAM-VBRI Press

E-mail: alika@iitg.ernet.in

Abstract

In this letter, optical limiting property of the insufficiently oxidized silicon oxide (SiO_x) thin films is reported. Films were deposited by Pulsed Laser Deposition technique using Q-switched Nd: YAG laser (532 nm) onto fused silica substrate at a substrate temperature of 400 °C by varying the O₂ pressure in the range of 5×10^-5 to 0.5 mbar. Energy Dispersive X-Ray spectra showed the increase in oxygen content with increasing O₂ pressure. Raman spectra of SiO_x films depicted the presence of micron sized clusters composed of nanocrystalline Silicon embedded in uniform matrix of oxidized amorphous Silicon. The open Z-scan of the thin films, under cw He-Ne laser irradiation, showed strong reverse saturation absorption (RSA) features and non linear absorption (NLA) coefficient, β, was found to be decreasing from 23.5 cm/W to 1.64 cm/W,  with increase in O₂ pressure from 5×10^-5 to 10^-1 mbar, respectively. Also, the SiO_x films except that with maximum oxygen content showed optical limiting, where limiting threshold increases with increasing transparency controlled by oxygen content. The key feature of the present work is the tunability in linear absorption, nonlinear RSA and optical limiting in the SiO_x films which can be used as novel material for optical switching application.

Keywords

Thin film, pulsed laser deposition, raman, Z-scan, optical limiting.