Maskless Electron Beam-Induced Etching of Diamond in Air: A Secondary Electron-Driven Mechanism

TL;DR

This paper introduces a maskless, high-precision electron beam-induced etching process for diamond in air, driven mainly by secondary electrons, enabling controlled nanofabrication without lithography.

Contribution

It reveals a secondary electron-driven mechanism for EBIE in gas environments, demonstrating controlled etching of diamond with high resolution and depth.

Findings

Achieved etch depths up to 212 nm and lateral resolution down to 200 nm.

Identified two etching regimes: molecule-limited and electron-limited.

Observed surface morphology changes enhancing etch yield.

Abstract

We report a direct, maskless electron beam-induced etching (EBIE) process for diamond in air, enabling high-precision patterning without lithography or plasma processing. Through a comprehensive analysis of electron-gas, electron-diamond, and gas-surface interactions in the SEM environment, we demonstrate that etching is predominantly governed by low-energy secondary electrons, which drive gas dissociation and radical generation. The resulting oxygen- and nitrogen-based radicals chemisorb on the diamond surface, form volatile carbon-containing species, and desorb under continued electron irradiation, enabling controlled material removal. The process exhibits two distinct regimes: a molecule-limited regime governed by gas flux and an electron-limited regime controlled by current density. Etch depths up to 212 nm and lateral resolution down to 200 nm are achieved. Time-dependent anisotropy is observed, with (100) surfaces transitioning to (111)-faceted morphologies, enhancing etch yield. These results establish a general secondary electron-driven mechanism for EBIE in gas environments, providing a maskless, damage-free nanofabrication route for diamond semiconductor and other chemically inert materials.