Germanium-based nearly hyperuniform nanoarchitectures by ion beam impact

TL;DR

This paper demonstrates a method to create disordered, nearly hyperuniform germanium nanoarchitectures using ion beam impact, resulting in unique optical properties and potential applications in electronics and photonics.

Contribution

It introduces a fabrication technique for disordered hyperuniform structures via ion beam impact on amorphous Ge, independent of beam size, suitable for large-scale semiconductor manufacturing.

Findings

Disordered Ge structures exhibit suppressed large-scale fluctuations.

Nanoarchitectures show enhanced light absorption and colorization.

Method is compatible with existing semiconductor fabrication processes.

Abstract

We address the fabrication of nano-architectures by impacting thin layers of amorphous Ge deposited on SiO$_{2}$ with a Ga$^{+}$ ion beam and investigate the structural and optical properties of the resulting patterns. By adjusting beam current and scanning parameters, different classes of nano-architectures can be formed, from elongated and periodic structures to disordered ones with a footprint of a few tens of nm. The latter disordered case features a significant suppression of large length scale fluctuations that are conventionally observed in ordered systems and exhibits a nearly hyperuniform character, as shown by the analysis of the spectral density at small wave vectors. It deviates from conventional random fields as accounted for by the analysis of Minkowski functionals. A proof of concept for potential applications is given by showing peculiar reflection properties of the resulting nano-structured films that exhibit colorization and enhanced light absorption with respect to the flat Ge layer counterpart (up to one order of magnitude at some wavelength). This fabrication method for disordered hyperuniform structures does not depend on the beam size. Being ion beam technology widely adopted in semiconductor foundries over 200 mm wafers, our work provides a viable pathway for obtaining disordered, nearly-hyperuniform materials by self-assembly with a footprint of tens of nanometers for electronic and photonic devices, energy storage and sensing.