Mask-less, high aspect ratio, high resolution electron-beam-induced etching of diamond

Vasilis Dergianlis, University of Duisburg-Essen, Duisburg, Germany
Dennis Oing, University of Duisburg-Essen, Duisburg, Germany
Martin Geller, University of Duisburg-Essen, Duisburg, Germany
Nicolas Wöhrl, University of Duisburg-Essen, Duisburg, Germany
Axel Lorke, University of Duisburg-Essen, Duisburg, Germany

Diamond has attracted significant attention as a promising material for a broad range of emerging applications, such as host material for NV -centers in future quantum information technologies [1] or as ultrasensitive nano-sensors [2]. Structuring the extremely stable material, especially without the need of resist is, however, highly challenging. First attempts have shown the general suitability of gas-assisted electron-beam-induced etching (EBIE), where water vapor in combination with an electron beam is used to create etch precursors directly at the diamond surface. Recently, EBIE anisotropic etching was used to texture diamond surfaces with typical length scales in the µm-range [3,4].

In this study, we report on high-resolution EBIE of undoped single crystal diamonds with high aspect ratio. We used a Scanning Electron Microscope (SEM) in a dual beam Focused Ion Beam (FIB) together with water vapor, which was injected by a needle directly onto the sample surface. Using this versatile and non-invasive technique, trenches with high-resolution of only 15 nm were precisely etched into the diamond sample. Using FIB milling, the cross section of each trench was obtained and used to calculate the respective aspect ratio, which ranged up to 4:1. The influence of the electron-beam energy and the flux on the resolution, the aspect ratio and the etch rate was studied. Our results show the possibility of high-resolution mask- and resistless patterning of diamond for nano-optical and electronic applications.

[1] Dutt et al., Science 316, 1312 (2007).
[2] Maze et al., Nature 455, 644 (2008).
[3] Martin et al., Phys. Rev. Lett. 115, 255501 (2015).
[4] Bishop, et al, ACS Nano 12, 2873 (2018).

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