Anti-reflection silicon with self-cleaning processed by femtosecond laser

The creation of functional surfaces has been studied extensively in the past due to their potential applications in corrosion resistance, anti-fouling, drag-reduction, and self-cleaning. In this paper, we present a simple method to fabricate an anti-reflection silicon surface with good self-cleaning effect by combined femtosecond laser processing with chemical modification. The reflectance of the prepared silicon is lower than 5%, and the surface exhibits a contact angle of 166° and a sliding angle of 3° for water. The water droplets can easily carry the contamination particles away from the prepared surface. More importantly, by changing the defocusing amount, we find that there are two different anti-reflection mechanisms. In the first mechanism, the light enters the object mainly through small surface nanostructures with dimensions greater than the wavelength of the incident light. In the second mechanism, the incident light is mostly reflected back and forth in the micro-hole and then absorbed by the silicon. In both mechanisms, the micro-hole structures are more suitable as an anti-reflection structure. Finally, photo-thermal conversion experiments are conducted on the prepared anti-reflection silicon surface.