Structural, linear and nonlinear optical study of zinc tetra-tert-butyl phthalocyanine thin film

Abstract

Zinc tetra-tert-butyl phthalocyanine (ZnTTBPc) thin films were deposited on cleaned glass substrates by thermal evaporation technique. The ZnTTBPc films undergo phase transformation from unstable amporphous into stable crystalline form when annealed at 473K as evidenced from the X-ray diffraction study. The UV–vis absorption spectral study revealed an increase in the optical band gap from 3.03eV for amorphous α-phase to 3.12eV for the crystalline β-phase of the film. The AFM topographic images display a significant change in the surface morphology of film due to thermal annealing. Nonlinear optical studies of stable β-phase were performed with picosecond (ps) laser pulses operating at a wavelength of 800nm. The present work is, the first such attempt to measure the third order nonlinear optical (NLO) coefficients of thermally evaporated β-phase ZnTTBPc thin films using ps laser pulses. The strong nonlinear absorption (NLA) and nonlinear refraction (NLR) coefficients (β and n2) i.e. 2×10−7cm/W and −7×10−11cm2/W, respectively, indicates thermally evaporated ZnTTBPc films could be a promising material for nonlinear optical device applications.