Effects of laser irradiation energy density on the properties of pulsed laser deposited ITO thin films

摘要

The properties of indium tin oxide (ITO) thin films, deposited at room temperature by simultaneous pulsed laser deposition (PLD), and laser irradiation of the substrate are reported. The films were fabricated from different Sn-doped In_2O_3 pellets at an oxygen pressure of 10 mTorr. During growth, a laser beam with an energy density of 0, 40 or 70 mJ/cm~2 was directed at the middle part of the substrate, covering an area of ～ 1 cm~2. The non-irradiated (0mJ/cm~2) films were amorphous; films irradiated with 40 mJ/cm~2 exhibited microcrystalline phases; and polycrystalline ITO films with a strong < 111 > > preferred orientation was obtained for a laser irradiation density of 70 mJ/cm~2. The resistivity, carrier density, and Hall mobility of the ITO films were strongly dependent on the Sn doping concentration and the laser irradiation energy density. The smallest resistivity of ～ 1 x 10~(-4) Ω cm was achieved for a 5 wt% Sn doped ITO films grown with a substrate irradiation energy density of 70 mJ/cm~2. The carrier mobility diminished with increasing Sn doping concentration. Theoretical models show that the decrease in mobility with increasing Sn concentration is due to the scattering of electrons in the films by ionized centers.