Top-down fabrication of Si nanotube arrays using nanoimprint lithography and spacer patterning for electronic and optoelectronic applications

Silicon (Si) nanotube arrays are expected to be a promising material for application in electronics and optoelectronics due to their large specific surface area with axially hollow spaces, whereas realizing smooth surfaces, high aspect ratios, and controlled dimensions remains a challenge. Moreover, it is also necessary to estimate various aspects of Si nanotubes such as their surface damage and anti-reflective properties. Here, we demonstrate a top-down fabrication of Si nanotube arrays with wall thicknesses of ∼40 to ∼10 nm using nanoimprint lithography (NIL) and spacer patterning. The Bosch process yields the nanotubes with smooth surfaces, long lengths (∼1000 nm), and no noticeable distortion or deformation. Raman scattering and electron spin resonance (ESR) measurements show their high crystal quality with a low density of surface dangling-bond defects. Furthermore, a significant enhancement of the anti-reflection effect of nanotubes and its dimension dependence is demonstrated and investigated by UV–Vis–NIR spectrophotometry as well as numerical simulations.