The relationship between the doping levels and some physical properties of SnO2:F thin films spray-deposited on optical glass

The relationship between the fluorine doping level and the electrical, structural and optical properties of the SnO2:F films are investigated using the Hall effect measurement set-up in van der Pauw configuration, the XRD patterns, UV-vis spectrophotometry and atomic force microscopy (AFM). The X-ray diffraction patterns taken at room temperature show that the films are polycrystalline. The preferred directions of crystal growth in the diffractogram of SnO2:F (FTO) films correspond to the reflections from the (1 1 0), (2 0 0), (2 1 1) and (3 0 1) planes. Thin film thickness and the grain size vary from 280 to 1545 nm and from 17.45 to 33.22 nm, respectively. AFM study reveals the surface of FTO to be made of nanocrystalline particles. The electrical study reveals that the films are degenerate and exhibit n-type electrical conductivity. The FTO films have a minimum resistivity of 5.29 x 10(-4) Omega.cm, carrier density of 0.09 x 10(20) cm(-3) and mobility of 377.02 cm(2)/V.s. The sprayed FTO film has the minimum sheet resistance of 5.69 Omega/cm(2) and the highest figure-of-merit of 204 x 10(-4) Omega(-1) at 700 nm. The resistivity attained for the doped film in this study is lower than the values reported for 20 wt.% fluorine-doped tin oxide films prepared from the aqueous solution of SnCl2 center dot 2H(2)O precursor. The highest visible transmittance (700 nm) of the deposited films is 91.8% for 25 wt.% fluorine-doped tin oxide films. The obtained results reveal that the structures and properties of the films are greatly affected by doping levels. These films are useful as conducting layers in electrochromic and photovoltaic devices.