Work function increase of indium-tin-oxide surfaces by atmospheric air plasma treatment with steady-state airflow

Atmospheric air-plasma treatment of indium-tin-oxide (ITO) surfaces has been investigated as an alternative to a conventional oxygen (O-2) vacuum plasma process. For this study, we devised an atmospheric air barrier plasma system having a dimension of 1000 X 600 nm(2) and successfully verified a possibility to ignite and maintain an atmospheric pressure discharge only in the ambient air. In particular, we used the steady-state airflow to generate more atomic oxygen radicals as oxygen gas during the vacuum plasma process and to prevent redeposition of the removed or transformed impurities onto the indium-tin-oxide substrate. The x-ray photoemission spectroscopy examination indicated that the adoption of the atmospheric-air plasma treatment reduced the surface content of carbon from 22.1% down to 8.5% and increased that of oxygen from 43% up to 57%. According to the photoelectron spectrometer (AC-1, RIKKEN) result, we obtained a work function of 5.11 eV for the treated ITO surfaces after 1 min treatment time, which is higher than that of 4.87 eV for the untreated ITO surface. Consequently, we can effectively remove the carbon contamination and increase the work function of the ITO surface by means of the atmospheric air plasma treatment with steady-state airflow. (c) 2005 American Vacuum Society.