Spectroscopic, microscopic, and electrical characterization of nanostructured SnO2:Co thin films prepared by sol–gel spin coating technique

Cobalt doped SnO2 thin films were prepared by sol–gel spin coating technique and influence of dopant concentration on structural, morphological and optical properties of thin films were investigated by XRD, XPS, FTIR, SEM, AFM, PL, UV–vis, and Hall effect measurement. All samples have a tetragonal rutile structure and the grain size decreases with increasing the doping concentration. XPS results clearly showed the presence of Co2+ ions into the SnO2. The SEM and AFM images reveal that the morphology of samples was affected by dopant. Conductivity type of the films changes from n-type to p-type with increasing Co-dopant above 3 mol% and electrical resistivity increases with increasing Co content. The optical band gap gradually decreases with improved cobalt concentration from 3.91 eV to 3.70 eV. The PL measurements revealed the decrease in intensity of blue emission lines and increase in green emission when content of Co is enhanced in the thin films.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Optical properties of the SnO2:Co nanostructured thin films have been investigated. ► The grain size of the samples was decreased with increasing of Co. ► The carrier type was changed from n-type to p-type in doping level above 3mol%. ► The direct optical band gap shifted to the lower energy. ► The green emission in PL spectra enhanced with Co doping.