Single-crystalline-like indium tin oxide thin films prepared by plasma enhanced atomic layer deposition

Abstract

In this study, indium tin oxide (ITO) thin films are prepared by plasma enhanced atomic layer deposition (PEALD) using alternating exposures to cyclopentadienyl indium and oxygen plasma for indium oxide (In₂O₃) and tetrakis (dimethylamido) tin and oxygen plasma for tin oxide (SnO₂). The cycle ratio of SnO₂-to-In₂O₃ is varied to investigate the effect on the film properties. The ITO films are examined using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Hall-effect probe measurement, and UV-visible transmittance measurement. It is found that the film thickness and Sn content can be well controlled by adjusting the SnO₂ cycle ratio. The lowest resistivity of 2.9 × 10⁻⁴ Ω cm, a high mobility of 52 cm² V⁻¹ s⁻¹ and an average optical transmittance of 89% are obtained at the SnO₂ cycle ratio of 5%. A very high doping efficiency of 86% is achieved. Furthermore, a single-crystalline-like structure is obtained, accounting for the high mobility of the films. The PEALD single-crystalline-like ITO films are suitable for electronic device applications requiring complex substrate deposition or sub-nanoscale thickness control.