Abstract
Transparent nano-crystalline thin films of Sn1?xLaxO2 (x = 0–0.1) were deposited on glass substrates using the cost-effective chemical spray pyrolysis method. The influence of La3+ concentration on the structural, morphological, linear and third-order nonlinear optical properties of the films were analysed. All the films possessed tetragonal crystalline structure, having a preferred (1 1 0) plane orientation irrespective of the doping content. Till a doping of 3 at%, the crystallite size showed a decreasing tendency. The fibrous morphology exhibited by the pure film got transformed into dense spherical microstructures at lower La doping levels. The films with lower doping content showed above 60% of transmittance in the visible wavelength region. The modification in the energy band gaps of the films were observed due to variations in the La concentration. The presence of various defects identified in the deposits by photoluminescence (PL) spectra analysis in the ultraviolet and visible region. Near white light emission was noticed in the films due to these defects. All the films exhibited third-order optical nonlinearity with an observed switching between reverse saturable absorption (RSA) and saturable absorption (SA). The films exhibited self-focussing and defocussing nature due to variation in the doping level. Sn0.94La0.06O2 film was identified as suitable for optical limiting application due to its least limiting threshold value. Hence, these spray pyrolyzed La doped films can be used in optical and nonlinear optical devices.
NSTL
Elsevier