Carbon content in PEALD-In2O3 thin films impact to its electrical and structural properties

In this paper, indium oxide (In2O3) thin films are prepared by plasma-enhanced atomic layer deposition (PEALD) using cyclopentadienylindium(I) (InCp) as the metal precursor and O2 plasma as the oxidant. The mechanism and effects of annealing temperature under the air atmosphere on optical, structural, and electrical properties of the films are investigated. The experimental results show that both of the as-deposited and annealed films are polycrystalline bixbyite-cubic structure. No significant influences on the optical properties are observed when the annealing temperature increases from 300 to 600 °C. However, it is confirmed the filling of oxygen vacancy defects by the in-diffused oxygen atoms from the annealing ambient. The carbon impurities resulting from the incompletely reacted InCp are found to be at the interstitial sites in the In2O3 lattice, which can be greatly removed by the annealing treatment. As a consequence, the electrical resistivity increases with increasing annealing temperature mainly related to the reduced carrier concentration. This paper is helpful for PEALD In2O3 films to be applied to optoelectronic devices where the suppression of the oxygen defects, carrier concentration, and carbon impurities are required.