Oxygen-controlled structures and properties of transparent conductive SnO2:F films

The morphology and properties of the transparent SnO 2 :F (FTO) films, deposited by RF magnetron sputtering at varying oxygen flows from 0∼3sccm, were examined. For FTO films deposited with 0∼1sccm O 2 , the polar unsaturated (101) planes were the preferred orientation, resulting in resistivity values as low as 10 −3  Ω cm, and the transparency of 86.5% in the visible range. The saturated (110) orientation planes associated with {101} facets formed knee twin crystallites for the FTO film prepared at 2sccm O 2 . Further increases of O 2 led to severe mis-orientation of the crystals. The average transparency in the visible range increased up to 95%, but these FTO films were hardly conductive due to the oversupply of O 2 . The optical band gaps became wide at first and then narrow again as the increases of the oxygen flow rates.