Surface cleaning of indium tin oxide by atmospheric air plasma treatment with the steady-state airflow for organic light emitting diodes

Abstract

Atmospheric air plasma treatment is being investigated as an alternative to a conventional oxygen (O 2) vacuum plasma process for cleaning ITO. We devised an atmospheric air barrier plasma system and used only an ambient air as discharge gas. In particular, we used the steady-state airflow to generate more atomic oxygen radicals during surface treatment of ITO and adopted the discharge image method for proofing the steady-state airflow effect. After the atmospheric air plasma treatment, the treated ITO substrates were investigated by contact angle measurement and by X-ray photoemission spectroscopy (XPS). It was found that the atmospheric air plasma treatment was quite effective in removing organic contamination on the ITO surface, causing a reduction in contact angle. The XPS 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%. We also showed that OLED fabricated from the atmospheric air plasma treated ITO exhibited superior brightness. Consequently, we can effectively remove carbon contamination and increase the work function of ITO surface by means of atmospheric air plasma treatment with steady-state airflow.