Investigation of optoelectronic properties of tin-doped indium oxide thin films and contact resistivity with silver film: Role of oxygen concentration variation during sputter deposition

We have investigated the optoelectronic properties like carrier concentration (NITO), mobility (µITO), work function (ϕITO), optical transmission and constants, and sheet resistance (Rsh) of tin-doped indium oxide (ITO) films with the variations in the oxygen flow rate during reactive sputter deposition with the Ar:O2 plasma. Initially, we also analyzed the generated Ar:O2 plasma parameters (ion energy and density, electron temperature, and energy distribution) using the Langmuir probe. The ITO films' optoelectronic properties were investigated systematically in as-deposited and annealed (150 to 200°C) conditions with varying O2 flow rates. By varying the O2 flow rate, we observed the carrier mobility (µITO) of the ITO films in the range of 31- 47 cm²/V-s, carrier concentration (NITO) in the range of 2.16 × 1019 - 5.22 × 1020 cm−3, and resistivity in the range of 3.57 × 10−4 - 8.95 × 10−4 Ω-cm. We were able to separate the roles of grain boundary and ionized impurity scatterings in modifying µITO as a function of NITO in the ITO films. Finally, using the transfer length method, we observed a contact resistivity of ∼3 mΩ-cm² from the ITO/Ag interface at the NITO of ∼4.08 × 1020 cm−3.