Thickness Dependence of Structural, Electrical and Optical Properties of Sputter Deposited Indium Tin Oxide Films

We report the results on low resistance indium tin oxide (ITO) thin films produced by r.f magnetron sputtering of a ceramic oxide target under Ar gas atmosphere. Thickness of the deposition has been tailor made from 0.74 μm to 2.58 μm by adjusting the time; the deposited films were characterized by XRD, TEM, electrical, optical and AFM studies. X-ray diffraction studies confirmed the presence of the ITO cubic phase with preferred orientation on (222) and (400) occurred for the films with thickness greater than 1.29 μm. It was observed that average grain size increases from 10.5 nm to 34.4 nm with increasing film thickness from 0.84 μm to 2.58 μm. The lowest sheet resistance and the lowest resistivity were measured at 1.68 μm and the corresponding values are found to be 12.36 Ω/square and 2.077×10^–3 Ω cm. The carrier concentration and mobility were calculated for 1.68 μm ITO thin films. The variation of refractive index and extinction coefficient with wavelength for the film deposited with 1.68 μm thickness were studied. It shows a high refractive index value of 1.92 at 550 nm which is in agreement with the reported value of 1.86 for the ITO films deposited by r.f magnetron sputtering. In the present work, ITO thin films possessing highly compact, void free and fully crystallized structure have been produced with an optimum thickness of 1.68 μm, which can be suitably and selectively used for solar cells, charge coupled devices and LCD applications.