Pulsed laser deposited Zn1-xTixO (0.000≤x≤0.050) thin films for tunable refractive index and nonlinear optical applications

Quenching of visible photoluminescence and observation of two photon absorption-induced photoluminescence in pulsed laser deposited Zn1−x Ti x O (0.000 ⩽ x ⩽ 0.050) thin films

“…In order to verify this abrupt change in thickness for x ⩾ 0.030, the deposition was repeated thrice for each and every value of x and the variation was found to be within 10%. The increase in the thickness is attributed to the lowering of the laser ablation threshold with the increase in Ti content [26,27].…”

“…The overall enhancement of the NBE peak in the Zn 1−x Ti x O films as compared to that in pure ZnO film can also be linked with the quantum size effect. The average crystallite size estimated from the XRD measurement is found to gradually decrease from 17 nm to 7.8 nm for 0.000 ⩽ x ⩽ 0.020 and thereafter increase to 26 nm for x > 0.020 [26]. Therefore, a weak quantum size effect could be possible for the x = 0.020 thin film sample resulting in the enhancement in the NBE along with suppression of the DLE band [41].…”

“…The absence of any pure Ti or TiO 2 peaks indicates the good substitutional replacement of Zn 2+ ions by the Ti 4+ ions. At higher concentrations of Ti (x > 0.020), the distortion in the (0 0 2) peak could be mainly due to excess free electrons which occupy the vacant space between the lattice positions [26]. Since the substitution of Ti for Zn atoms undergoes a mutual replacement of Zn 2+ ions by Ti 4+ ions, two excess free electrons are added in the process which remain as free carriers.…”