Abstract
In this manuscript, we outline a reliable procedure to manufacture photonic nanostructures from single-crystal diamond (SCD). Photonic nanostructures, in our case SCD nanopillars on thin (<1 m) platforms, are highly relevant for nanoscale sensing. The presented top-down procedure includes electron beam lithography (EBL) as well as reactive ion etching (RIE). Our method introduces a novel type of inter-layer, namely silicon, that significantly enhances the adhesion of hydrogen silsesquioxane (HSQ) electron beam resist to SCD and avoids sample charging during EBL. In contrast to previously used adhesion layers, our silicon layer can be removed using a highly-selective RIE step, which is not damaging HSQ mask structures. We thus refine published nanofabrication processes to ease a higher process reliability especially in the light of the advancing commercialization of SCD sensor devices.
Highlights
In recent decades, the use of optically active point defect, i.e., color centers, in single-crystal diamond (SCD) as atom-sized, solid-based quantum systems has emerged in various fields [1,2]
Our method introduces a novel type of inter-layer, namely silicon, that significantly enhances the adhesion of hydrogen silsesquioxane (HSQ) electron beam resist to SCD and avoids sample charging during electron beam lithography (EBL)
The state-of-the-art masks for SCD nanostructuring are EBL written structures consisting of hydrogen silsesquioxane (HSQ)
Summary
The use of optically active point defect, i.e., color centers, in single-crystal diamond (SCD) as atom-sized, solid-based quantum systems has emerged in various fields [1,2]. Both properties render fabricating SCD nanostructures challenging: Top-down methods for nanofabrication will use lithography, typically electron beam lithography (EBL), as well as etching. The first can leave trace amounts of the etchant on the SCD surface and the second is technically demanding considering safety and reactor corrosion In this manuscript, we present a method to overcome two previously not satisfactorily addressed challenges in SCD nanofabrication, namely sample charging as well as non-optimal resist adhesion. The silicon adhesion layer survives the subsequent wet-chemical removal of the HSQ mask (Figure 1g) and can be reused for a second round of processing (Figure 1h–l). In this second processing, we form the pillars. The method presented here has been filed for a patent (EP19198772.6)
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