Mask-free fabrication of inverted-pyramid texture on single-crystalline Si wafer

• Inverted-pyramid textures are fabricated on Si without using a pre-patterned mask.
• The process is based on the pulsed laser interference and chemical etching.
• Uniform textures are obtained with a minimum reflectance of 15.8%.

We here show that inverted-pyramid (IP) textures can be fabricated on single-crystalline Si wafer by simply irradiating the surface with a nanosecond pulsed laser at 532 nm, followed by alkali etching. This process is fundamentally based on the laser-induced melting of material. When exposed to three interfering laser beams, the surface was locally melted in a periodic fashion in accordance with the interference pattern. This generated concave holes on the surface because the melted material overflowed and condensed at the periphery. When subsequently etched by KOH, the internal morphology of the concave holes changed into an IP shape as a result of the position-dependent different etching rates. Uniform IP structures could be obtained with a minimum reflectance of 15.8%.