Structural and optical characteristics of nickel bis(acetylacetonate) thin films as a buffer layer for optoelectronic applications

Abstract

Due to the insisted requirement for low cost and a nontoxic buffer layer for the most of optoelectronic applications, optical properties of nickel bis(acetylacetonate), Ni(acac)2, are examined for this prospect. This research represents a deep investigation of the linear and nonlinear optical properties of thermally evaporated Ni(acac)2 thin films accompanied by structural and morphological characterization. The thermogravimetric thermogram revealed the stability of Ni(acac)2 up to 461 K. The structural properties of the deposited film are investigated using x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The XRD and HRTEM results revealed the polycrystalline nature of as-deposited film with [100] preferred orientation and average crystallite size about 108 nm. Furthermore, both atomic force microscopy, AFM, and field emission scanning electron microscopy, FESEM, are employed to inspect the surface topography of the prepared film. In addition, the spectrophotometric method is utilized for evaluating the linear and nonlinear optical constants of the prepared films. The dispersive parameters of Ni(acac)2 is determined and analyzed in the point of view of the single oscillator model. The wide band gap (Eg ˜ 3.6 eV), high transparency and the small value of Urbach energy (Eu ˜ 76 meV) qualify this material to be utilized as a buffer layer. The nonlinear optical parameters of the fabricated film such as nonlinear refractive index and third order optical susceptibility are estimated. Both molecular polarizability and the optical electronegativity of Ni(acac)2 thin film is calculated and found to be 3.18 Å3 and 1.98, respectively. The obtained results give the opportunity to nickel acetylacetonate for buffering most of the commercial optoelectronic applications.