Fluorinated tin oxide (FTO) deposited at room temperature: Influence of hydrogen and oxygen in the sputtering gas on the optical and electrical properties

The optical and electrical properties of fluorinated tin oxide (FTO) films deposited at room temperature by sputtering were investigated. In addition to small amount of oxygen to preserve highly transparent films, electrical resistivity become decreased two orders of magnitude by using appropriate hydrogen content in the sputtering gas. Films deposited with Ar(93%)/O2(5%)/H2(2%) gas mixture show maximal values of conductivity, charge carrier density and mobility as well as excellent transparency. Taking into account the film characterization carried out by Rutherford backscattering spectrometry (RBS), a mechanism is proposed to explain the observed optical and electrical dependence with the hydrogen content in the film.