Simple colloidal lithography method to fabricate large-area moth-eye antireflective structures on Si, Ge, and GaAs for IR applications

Abstract

A two-step colloidal lithography process (Langmuir–Blodgett dip coating + reactive ion etching)was developed to fabricate single and double-sided moth-eye structures in Si, Ge, and GaAs for antireflection applications in the IR. Large increases in transmittance were obtained in all threematerial platforms (up to 97% single-side and 91% absolute transmittance) over the λ = 4−20+ μm region. Effective medium theory and the transfer matrix method were used to predict IR optical response of moth-eye substrates as well as investigate the effect of protuberance shape on antireflectance behavior. Overall, it is demonstrated that colloidal lithography and etching provide an easy and generic way to synthesize moth-eyes in different IR material platforms.