Oblique-Angle Sputtering Effects on Characteristics of Nanocolumnar Structure Anisotropic Indium Tin Oxide Films

We present a nanocolumnar structure anisotropic indium tin oxide (ITO) film deposited at different oblique angles by a radio-frequency magnetron sputtering system. Three dominant diffraction peaks were observed. The location of peaks SnO2(110), In2O3(222), and In2O3(400) increases from 29.39, 31.34, and 36.34 degrees to 29.45, 31.60, and 36.48 degrees, respectively, as the sputtering oblique angle increases from 0 to 80 degrees. This may be attributed to a high incorporation of oxygen into the film deposited at a high oblique angle. An anisotropic ITO film with a higher oxygen content has a smaller lattice constant, a larger bandgap, a higher resistivity, and a degradation of crystallization. As the flux arrival angle alpha increases, the absorption edge of the spectra demonstrated a blueshift. The blueshift may result from the Burstein-Moss effect due to the increase in the oxygen content in the anisotropic ITO film or to the quantum confinement effect caused by the exciton quantization in the ITO film.