Formation of antireflective surfaces

A method for etching nanostructures in a substrate for creating an anti-reflective surface, the method comprising:

• depositing a block copolymer on the substrate, wherein:
• the block copolymer comprises a first block and a second block;
• and
• the first block forms one or more first domains and the second block forms one or more second domains;
• applying a precursor to the block copolymer to generate an infiltrated block copolymer on the substrate, wherein:
• the precursor infiltrates the one or more first domains;
• the precursor does not infiltrate the one or more second domains;
• and
• the precursor generates a material in the one or more first domains;
• applying a removal agent to the infiltrated block copolymer to generate a template comprising a plurality of dots of the material on the substrate, wherein:
• the removal agent is effective to remove the first block and the second block from the substrate, and is not effective to remove the material in the one or more first domains;
• and
• anisotropically and isotropically etching the substrate to produce a nanotexture having a plurality of nanostructures;
• wherein:
• the template masks the substrate during etching;
• and
• the anisotropic and isotropic etching is performed simultaneously to produce the nanotexture having a monotonically varying effective refractive index between a surface of the nanotexture and an interior of the nanotexture.