Microtubes and nanomembranes by ion-beam-induced exfoliation of $\beta$-Ga$_{2}$O$_{3}$

TL;DR

This paper introduces a novel ion-beam process to create $eta$-Ga$_{2}$O$_{3}$ microtubes and nanomembranes, enabling scalable, dopable, and high-quality nanostructures for various applications.

Contribution

It demonstrates a new ion implantation technique for fabricating and transferring $eta$-Ga$_{2}$O$_{3}$ nanostructures with controlled doping and improved reproducibility.

Findings

Microtubes form via strain-induced rolling under specific irradiation conditions.

Nanomembranes can be unrolled and transferred after annealing.

Damage from ion implantation can be effectively recovered at ~500°C.

Abstract

This paper reports an innovative process to fabricate $\beta$-Ga$_{2}$O$_{3}$ microtubes and nanomembranes based on ion implantation in (100)-oriented single-crystals. We show that, under specific flux and fluence conditions, the irradiation-induced strain profile promotes the detachment and rolling-up of a thin surface layer, forming a microtube. The strain-disorder interplay was investigated in detail for Cr-implanted $\beta$-Ga$_{2}$O$_{3}$ with a range of complementary methods, showing an excellent agreement between experimental and simulation data, and suggesting an exfoliation mechanism that is correlated with the anisotropic nature of the $\beta$-Ga$_{2}$O$_{3}$ monoclinic system and its easy-cleavage planes. Moreover, these microtubes can be unrolled upon a subsequent annealing step, resulting in nanomembranes with bulk-like crystalline quality that can be transferred to other substrates. The recovery of the implantation-induced damage under thermal annealing has also been studied, showing a remarkable recovery at moderate temperatures (~500 {\deg}C). This observation underscores the potential of this method for the scalable production of nanomembranes with improved reproducibility compared to conventional mechanical exfoliation techniques. Importantly, such exfoliation can be done employing different ions, providing simultaneous $\beta$-Ga$_{2}$O$_{3}$ doping, chosen to control the structural, optical, magnetic and electrical properties of the nanomembranes, thus tailoring them to fit the desired applications.