Effect of sputtering power on the structural and optical properties of RF magnetron sputtered ITO films

The structural and optical properties of RF magnetron sputtered ITO films without in situ substrate heating and post-deposition annealing are investigated. The structure and orientation of ITO films strongly depends on the energy of the sputtered particles arriving at the substrate. As the sputtering power increases from 15 to 100 W, the preferred orientation of the ITO film changes from (222) to (400). It is observed that the lattice constant of the film increases initially as sputtering power increases from 15 to 50 W and then decreases with further increase of sputtering power. The higher the sputtering power, the smaller the oxygen content of the film. The oxygen deficiency is used to explain the loss of transmittance or blackening of ITO films deposited at high sputtering power. Several material parameters, such as optical constants and energy gap, have been derived and discussed. The figure of merit of the films ranges from 81.3 to 117.6 Omega -1.