Multiple Aztec steps as an angle resolved micro-spectrometer by grayscale ice lithography

For decades, Aztec steps have been widely attained because of the potential application as an angle-resolved micro-spectroscope. However, the challenge in replicating multiple steps with less than 1 nm precision hinders the Aztec steps to be commercialized. Although grayscale electron beam lithography (G-EBL) on PMMA (polymethyl methacrylate) has been tried but the surface roughness as well as the flatness still remains a big issue. This work evaluates the grayscale e-beam lithography in amorphous solid water (ASW), nicknamed as ice lithography, for Aztec steps by numerical simulation based on Monte Carlo algorithm. For comparison, grayscale electron beam lithography in PMMA was included in the simulation. Furthermore, simulation using finite difference and time domain (FDTD) method was also carried out to theoretically characterize the angle-resolved spectra by the numerically modeled Aztec steps in ASW and PMMA, respectively. Our results show that grayscale ice lithography on ASW is able to replicate Aztec steps with much smother surface and better flatness than that on PMMA, giving rise to significantly improved spectral resolution.