Fluorine-doped ZnO transparent conducting thin films prepared by radio frequency magnetron sputtering

Fluorine-doped ZnO transparent conducting thin films were prepared by radio frequency magnetron sputtering at 150 oC on glass substrate. Thermal annealing in vacuum was used to improve the optical and electrical properties of the films. X-ray patterns indicated that (002) preferential growth was observed. The grain size of F-doped ZnO thin films calculated from the full-width at half-maximum of the (002) diffraction lines is in the range of 18-24 nm. The average transmittance in visible region is over 90% for all specimens. The specimen annealed at 400 oC has the lowest resistivity of 1.86 x 10-3 Ω cm, the highest mobility of 8.9 cm2 V-1 s-1, the highest carrier concentration of 3.78 x 1020 cm-3, and the highest energy band gap of 3.40 eV. The resistivity of F-doped ZnO thin films increases gradually to 4.58 x 10-3 Ω cm after annealed at 400 oC for 4 h. The variation of the resistivity is slight.