Effect of annealing on the spectral and nonlinear optical characteristics of thin films of nano-ZnO

Abstract

The annealing effect on the spectral and nonlinear optical (NLO) characteristics of ZnO thin films deposited on quartz substrates by sol-gel process is investigated. As the annealing temperature increases from 300–1050 °C, there is a decrease in the band gap, which indicates the changes of the interface of ZnO. ZnO is reported to show two emission bands, an ultraviolet (UV) emission band and another in the green region. The intensity of the UV peak remains the same while the intensity of the visible peak increases with increase in annealing temperature. The role of oxygen in ZnO thin films during the annealing process is important to the change in optical properties. The mechanism of the luminescence suggests that UV luminescence of ZnO thin films is related to the transition from conduction band edge to valence band, and green luminescence is caused by the transition from deep donor level to valence band due to oxygen vacancies. The NLO response of these samples is studied using nanosecond laser pulses at off-resonance wavelengths. The nonlinear absorption coefficient increases from 2.9×10−6 to 1.0×10−4 m/W when the annealing temperature is increased from 300 to 1050 °C, mainly due to the enhancement of interfacial state and exciton oscillator strength. The third order optical susceptibility χ(3) increases with increase in annealing temperature (T) within the range of our investigations. In the weak confinement regime, T2.4 dependence of χ(3) is obtained for ZnO thin films. The role of annealing temperature on the optical limiting response is also studied.

Optical Absorption Measurement of Synthesized ZnO using Ultra Violet-Visible Spectrophotometer

“…As reported by [5] ZnO absorbed only in the UV region because of its large bandwidth of 3.2eV (λ = 380 nm). ZnO exhibited two emission bands, ultraviolet (UV) emission band and another in the green region [6]. Also they found that the intensity of the UV peak remained the same, while the intensity of the visible peak increase with the increase in the annealing temperature.…”

ZnO nanoparticle-containing emulsions for transparent, hydrophobic UV-absorbent films

“…Variation of the size leads to a shift of the UV absorption step [11,12] and allows for the preparation of almost completely transparent films using very small particles [9]. Films containing ZnO nanoparticles can be prepared by a variety of methods, e.g.…”

“…Films containing ZnO nanoparticles can be prepared by a variety of methods, e.g. electrochemical, vacuum, and chemical bath deposition [8,10,13,14], the solution dipping template method [15], sol-gel processes [5][6][7]9], and magnetron sputtering [16].…”

“…The properties of zinc oxide nanoparticles [2,3] allow the preparation of UV-absorbent films [4][5][6][7][8][9][10], with size and shape of the particles being factors that can be used to tune the properties of the films. Variation of the size leads to a shift of the UV absorption step [11,12] and allows for the preparation of almost completely transparent films using very small particles [9].…”

Preparation of ZnO/CdS/BC Photocatalyst Hybrid Fiber and Research of Its Photocatalytic Properties

“…a template in the synthesis of various inorganic nanostructures. Various methods have been reported for the synthesis of ZnO/CdS nanorods including colloidal chemical synthesis [16], electrochemical deposition [23], chemical bath deposition technique [24], facile chemical route [25], combined sol-gel/hydrothermal/SILAR method [26], chemical precipitation method [27], and sonochemical synthesis [28]. Among these methods, coprecipitation process is a simple and lowcost method that can be performed at low temperature and ambient pressure.…”