Dependence of Nanostructure and the Optical Properties of Ni Thin Films with Different Thicknesses on the Substrate Temperature

Abstract

Nickel films with the thicknesses of 30 and 120 nm were deposited on glass substrates, at different substrate temperatures (313 to 600 K) under uhv condition. The nano-structure of the films and mean diameter of grains was obtained for each films using atomic force microscopy (AFM). Their optical properties were measured by spectrophotometry in the spectral range of 190-2500 nm. Kramers-Kronig method was used for the analysis of the reflectivity curves. The Effective Medium Approximation (EMA) analysis was used to determine the values of volume fraction of voids (fv)and establish the relationship between the nanostructure of the film and EMA predictions. Qualitatively good agreements between structure Zone Model (SZM) as a function of substrate temperature and the values of (fv), is achieved. There is good agreement between these values and the results of mean diameter of grains for Ni films too. The absorption peaks of Ni thin films at ~ 1.4 eV and 5 eV are observed, with an additional bump at about 2 eV. The 1.4 eV peak is in particular much stronger than that obtained in earlier works on Ni thin films (Johnson and Christy (1974)) and on bulk Ni sample (Lynch et al (1971) and Ehrenrich et al (1963)). This is resulted from producing thin films under uhv condition. The conductivities σ1 and σ2 calculated from ɛ1 and ɛ2 for Ni films and were plotted vs energy.