Study On Highly Transparent Conductive FTO Thin Films By Reactive Magnetron Sputtering

F-doped SnO₂（FTO）thin films have attracted much attention due to its excellent transparent conductive properties.However,there are few systemic studies on the preparation of highly transparent conductive FTO thin films by magnetron sputtering at low temperature until now.Therefore,with Sn+SnF₂ as targets,FTO thin films were prepared by reactive magnetron sputtering under the atmosphere of Ar+O₂ in this paper.Under different sputtering powers,SnF₂ contents and substrate temperatures（T_S）,the effects of O₂ flux on the structure,optical,and electrical properties of FTO films were systemically investigated by interference microscopy,X-ray diffraction,the Hall Effect measurement system and UV-Vis spectrophotometry.The results show that the O₂ flux for preparing FTO films increases with increasing sputtering power,but it has little change with the increase of SnF₂ content and T_S.At different sputtering powers,SnF₂ contents and T_S,the deposition rate of FTO films has no significant changes as O₂ flux increases.At the same time,FTO films show a transition from amorphous to polycrystalline state and the preferred orientation of crystalline films gradually transforms from（101）and/or（002）plane to（211）or（200）plane as O₂ flux increases.In addition,it is found that increasing sputtering power can obviously increase the deposition rate,but has no significant effect on the crystallinity of FTO films.With increasing Sn F₂ content,both the deposition rate and the crystallinity of the films have minor changes.As T_S increases,the crystallinity of the films improves significantly,while their deposition rate has no obvious changes.At different sputtering powers,Sn F₂ contents and T_S,the carrier concentration of FTO films first increases and then decreases or decreases monotonously,and the mobility first increases and then decreases,thus the resistivity first decreases and then increases with increasing O₂ flux.When the resistivity reaches the minimum value,the corresponding optimum O₂ flux increases with the increase of sputtering power,while it decreases as the SnF₂ content or T_S increases.Under the optimized O₂ fluxes,the carrier concentration of FTO films first increases slightly and then decreases,while the mobility decreases obviously with increasing sputtering power,which results in an increase of film resistivity.With increasing SnF₂ content or Ts,the resistivity of FTO films shows a trend of first increase and then decrease,because the carrier concentration and mobility of the films first increase and then decrease.At present study,the optimum sputtering power,SnF₂ content and T_S are 30 W,15wt%and 200°C,respectively.Under this optimum condition,FTO film has a minimum resistivity of 1.76×10^-3Ω·cm,which is better than previously reported results.At different sputtering powers,SnF₂ contents or T_S,the average transmittance in visible light range of FTO films first increases rapidly and then increases slowly and eventually tends to constant as O₂ flux increases.After the average transmittance keeps constant,its value first increases and then decreases with increasing SnF₂ content,but has no significant changes with increasing sputtering power or T_S.On the whole,FTO film can achieve an average transmittance over 80%when its resistivity reaches a minimum value.As for the energy gap（E_g）of FTO films,it first increases rapidly and then tends to saturation with increasing O₂ flux under different sputtering powers,SnF₂contents or T_S.