Periodic atmospheric plasma substrate treatment to improve the hydrophobicity of sputtering PTFE films

This study employed atmospheric plasma (AP) pretreatment to enhance the hydrophobicity of polytetrafluoroethylene (PTFE) thin films. When a PTFE thin film was deposited on the substrate pretreated with AP, the deposition followed the Frank-van der Merwe mode at hydrophilic regions and the Volmer–Weber mode at hydrophobic regions, thereby causing the PTFE thin film to have continuous bumps. In accordance with the Wenzel and Cassie equation, increasing the surface roughness of hydrophobic materials increased their hydrophobicity. The water contact angle increased from 100° to 110° after deposited PTFE thin film on substrate pretreated with AP. Finally, the water contact angle further increased to 115° after annealed in nitrogen gas. A salt spray test demonstrated that the hydrophobic PTFE thin film had excellent corrosion resistance and stability. This hydrophobic film preparation technology can be used for the protective film of electronic device, sensor, solar cell and so on.