The ITO films had outstanding elect

The ITO films had outstanding electrical properties when the I222/ I400 ratio was closer to 1. When the Sn element replaced the In element in the crystal lattice of In2O3 and existed in the form of SnO2, an electron was contributed to the conduction band and oxygen vacancy was generated in an anoxic state. The relative strength of (400) peak for the ITO target increased , indicating that the oxygen vacancy concentration increased and the concentration of Sn in the target was high, along with a high Sn the concentration in the prepared ITO films, in consistent with the results in Table 2. The higher I222/I400 ratio of the ITO films and higher content of In3+ and O2 were favorable for the formation of the indium oxide network [15]. Therefore, an increase in the oxygen content in the In2O3 lattice network would lead to reduction of oxygen vacancies, making the (222) peak dominant. According to frank-kostlin's model [22], two doped Sn4+ can bind one extra oxygen to the lattice gap nearby, forming electrically neutral composite particles, destroying the formation of indium oxide lattice network and increasing oxygen vacancy concentration. When ITO target is bombarded by high-energy ions, the concentration of Sn in the ITO film prepared using the target A with better element distribution uniformity is higher and the oxygen vacancy is easier to form. Therefore, with the increase of tin concentration in ITO films, the preferred orientation of ITO films is at peak (400).