Vanadium doping induces surface morphological changes of CuInS2 thin films deposited by chemical spray pyrolysis

Abstract

Pristine and vanadium (V) doped CuInS2 (CIS) thin films were grown on glass substrate using home-built chemical spray pyrolysis unit. The structural, morphological, optical and electrical properties of pristine and V doped CIS thin films have been systematically inspected. The scanning electron and atomic force microscopic (SEM and AFM) images show the well-interconnected CIS nanoparticles changed to nanorods like morphology with respect to V doping level and also the number density of the nanorods increases with doping level. Furthermore, the formation of CIS nanoparticles and V doped CIS nanorods are authentically confirmed by the transmission electron microscopic (TEM) images. Both pristine and V doped CIS thin films exhibit the body centered tetragonal crystal structure along with polycrystalline nature which is characterized using X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns. The presence of dopant and host elements is confirmed by X-ray photoelectron and energy dispersive X-ray spectroscopic (XPS and EDX) analyses. The decreases of orbital energy gap values are observed using UV–Vis absorption spectra according to V doping level into the CIS lattice sites. A continuous suppression of defect related Cu-Au orderings are observed via Raman spectra as a function of V doping which also indicate the V doping significantly involved during deposition and improve the structural quality of the chalcopyrite CIS film. The electrical properties of CIS films transform enormously, switching from hole dominated (0.3782Scm−1) p-type to electron dominated (27.16Scm−1) n-type from 4wt.% of V doping. It anticipates that this kind of self-assembled 1D CIS nanostructure will give huge interest to tune their physicochemical properties.