Properties of fluorine and tin co-doped ZnO thin films deposited by sol–gel method

• F and Sn co-doped ZnO thin films were synthesized by sol–gel method.
• The effects of different F doping concentrations were investigated.
• The co-doped nanocrystals exhibit good crystal quality.
• The origin of the photoluminescence emissions was discussed.
• The films showed high transmittance and low resistivity.

Highly transparent and conducting fluorine (F) and tin (Sn) co-doped ZnO (FTZO) thin films were deposited on glass substrates by the sol–gel processing. The structure and morphology of the films are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) with various F doping concentrations. SEM images showed that the hexagonal ZnO crystals were well-arranged on the glass substrates and the HRTEM images indicated that the individual nanocrystals are highly oriented and exhibited a perfect lattice structure. Owing to its high carrier concentration and mobility, as well as good crystal quality, a minimum resistivity of 1 × 10−3 Ω cm was obtained from the FTZO thin film with 3% F doping, and the average optical transmittance in the entire visible wavelength region was higher than 90%. The X-ray photoelectron spectroscopy (XPS) study confirmed the substitution of Zn2+ by Sn ions and Room temperature photoluminescence (PL) observed for pure and FTZO thin films suggested the films exhibit a good crystallinity with a very low defect concentration.