Hydrophobicity enhancement of Al_2O_3 thin films deposited on polymeric substrates by atomic layer deposition with perfluoropropane plasma treatment

摘要

The optoelectronics devices such as organic light emitting diodes are greatly vulnerable to moisture, which reduces their functionality and life cycle. The Al_2O_3 thin films are mostly used as barrier coatings in such electronic devices to protect them from water vapors. The performance of the Al_2O_3 barrier films can be improved by enhancing their hydrophobicity. Greater the hydrophobicity of the barrier films, greater will be their protection against water vapors. This paper reports on the enhancement of hydrophobicity of Al_2O_3 thin films through perfluoropropane (C_3F_8) plasma treatment. Firstly, good quality Al_2O_3 films have been fabricated through atomic layer deposition (ALD) on polyethylene naphthalate (PEN) substrates at different temperatures. The fabricated films are then plasma treated with C_3F_8 to enhance their hydrophobicity. Hydrophobic Al_2O_3 thin films have shown good morphological and optical properties. Low average arithmetic roughness (Ra) of 1.90 nm, 0.93 nm and 0.88 nm have been recorded for the C_3F_8 plasma treated films deposited at room temperature (RT), 50 ℃ and 150 ℃, respectively. Optical transmittance of more than 90% has been achieved for the C_3F_8 plasma treated films grown at 50 ℃ and 150 ℃. The contact angle has been increased from 48° ± 3 to 158° ± 3 for the films deposited at RT and increased from 41° ±3 to 148° ±3 for the films deposited at 150℃.