AVS 47th International Symposium
    Thin Films Thursday Sessions
       Session TF-ThA

Paper TF-ThA6
Effects of Excess Oxygen Introduced during Sputter Deposition and Post Annealing under a High Oxygen Pressure on Carrier Mobility in Indium-tin Oxide Films

Thursday, October 5, 2000, 3:40 pm, Room 203

Session: Transparent Optical Coatings
Presenter: N. Kikuchi, Kanazawa Institute of Technology, Japan
Authors: N. Kikuchi, Kanazawa Institute of Technology, Japan
E. Kusano, Kanazawa Institute of Technology, Japan
E. Kishio, Kanazawa Institute of Technology, Japan
A. Kinbara, Kanazawa Institute of Technology, Japan
H. Nanto, Kanazawa Institute of Technology, Japan
Correspondent: Click to Email
Post-annealing for tin dope indium oxide films deposited at a low substrate temperature is sometimes needed to improve their optical properties. While the transparency in the visible range is enhanced by the annealing, the electrical conductivity of the film is deteriorated generally. The deterioration in the electrical conductivity is not only because of the reduction in carrier density, but also because of the reduction in carrier mobility. The reduction in the carrier mobility is thought to strongly relate to the introduction of excess oxygen into or on the film by the annealing. In this paper, indium tin oxide films with excess oxygen was prepared by deposition with a high oxygen concentration or by post-annealing under a high oxygen pressure in order to discuss its effects on electron mobility have been investigated. ITO films were deposited on glass substrates by r.f. sputtering under various oxygen concentrations in the discharge gas (0.3-100 %). Substrate temperature was kept at 773 K during deposition. Single phase of In@sub 2@O@sub 3@ was observed for all films deposited. A minimum resistivity of 1.8x10@super -4@ @ohm@cm was obtained for a film with a Sn concentration of 8 wt%, deposited at an O@sub 2@ concentration in the discharge gas of 0.3 %. With increasing oxygen concentration in the discharge gas from 0.3 % to 100 %, the Hall mobility decreased from 45 cm@super 2@V@super -1@s@super -1@ to 27 cm@super 2@V@super 1@s@super -1@ and the carrier density decreased from 1.0x10@super 21@ cm@super -3@ to 1.0x10@super 19@ cm@super -3@. By the post-annealing at 473 K for 30 min. in air, the Hall mobility of 27 cm@super 2@V@super -1@s@super -1@ increased to 37 cm@super 2@V@super -1@s@super -1@ and the carrier density of 1.0x10@super 19@ cm@super -3@ increased to 2.0x10@super 19@ cm@super -3@. The similar behavior of the Hall mobility and carrier density was observed for an ITO film annealed in O@sub 3@. These increases in the Hall mobility and carrier density during a low temperature annealing is thought to relate to desorption of excess oxygen existed at grain boundaries or the surface of the films because the annealing temperature is too low to improve the film crystallinity further and because it is hard to assume the formation of oxygen vacancies under the condition of the annealing. The results obtained support the hypothesis that the oxygen introduced into grain boundaries or adsorbed at the surface of the films act as charge traps and carrier scattering centers.