Improvement in properties of indium tin oxide thin films by electron beam irradiation

Indium tin oxide (ITO) thin films were conventionally prepared by using RF sputtering with 4 torr of Ar working pressure, and then annealed by electron beam irradiation as a rapid crystallization method. DC power was varied in the range of 1~4 keV to control the density of electron dose, with fixed RF power of 200 W and 3 min of irradiation. The crystallinity of the samples was gradually improved with increase of the DC power, especially the crystalline direction of (222). The electrical properties of the electron beam irradiated ITO thin films were remarkably improved to achieve carrier concentrations of ~1020 cm-3, Hall mobility of 31~42 cm2/Vs, and resistivity of ~10-4 Ω cm. Simultaneously, improvement of the optical properties was also attained, such as increase of transmittance to ~90% and of the optical bandgap from 3.46 to 4.07 eV. Electron beam irradiation onto ITO thin films as a rapid annealing method could be an excellent candidate for crystallization.