3D micromorphology-contact resistance-conductivity insights of quasi 2D Cd1-xPbxS thin films: Investigation based on stereometric and fractal analysis

Abstract

In this work, stereometric and fractal analysis of Lead (Pb) doped Cadmium sulfide (CdS) thin films synthesized by pulsed laser deposition is reported. The atomic force microscopy (AFM) data were studied to understand the influence of doping on micromorphology, contact resistance and conductivity of CdS films. Stereometric analysis exhibits a non-linear behavior, from Pb doping, in surface roughness with non-Gaussian height distribution in addition to influence on microtexture surface porosity and elastic deformation. A sinusoidal behavior of local surface smoothness with lesser surface complexities for higher Pb concentrations is confirmed from the Hurst coefficient and fractal dimension values of the film surfaces. Surface entropy reveals a uniform deposition of the thin films while a non-linear variation in surface percolation is justified from fractal succolarity values. The tuning of contact resistance between window and buffer layer and thus, enhancement in efficiency of Cadmium indium gallium selenide (CIGS) solar cells is possible with Pb doping in CdS thin films, in the framework of fractal dimension. Additionally, the enhancement in conductivity of Cd1-xPbxS thin films is attributed to surface smoothening process mediated by the large values of Hurst coefficient and autocorrelation length with a consequent decline in RMS roughness.