Sn doped zinc oxide (ZnO) films have been successfully synthesised via the sol-gel method by spin coating onto glass substrates followed by annealing in air at 600 degrees C for 2 h. The X-ray diffraction patterns of the annealed specimens exhibit well defined diffraction peaks indexed to the hexagonal wurtzite structure with no trace of tin metal, oxides or binary zinc tin phases, indicating that metallic Sn entered the ZnO lattice in the form of Sn4+. Sn dopant concentration caused the carrier concentration and the grain size change, thus affecting the infrared emissivity of ZnO films. When the ZnO film was doped with 6 at-% Sn, the infrared emissivity decreased as the temperature increases, which was favourable for the application in infrared stealth technology.