Reliable Nanofabrication of Single-Crystal Diamond Photonic Nanostructures for Nanoscale Sensing

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 μm) 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.

Plasma Treatments and Light Extraction from Fluorinated CVD-Grown (400) Single Crystal Diamond Nanopillars

“…We refer the reader to earlier studies on the nanofabrication published earlier [12]. In brief: we employed a cold-cathode scanning electron microscope (SEM) (Hitachi S4500), equipped with RAITH Elphy software to perform electron beam-lithography (EBL).…”

“…The enhancement of photoluminescence count-rate arising from NV − relaxation can be achieved with waveguiding effect. The easiest approach to do so is nanofabrication [12]. Diamond is nevertheless an insulator, which makes it a challenging material to perform standard lithogrpahy by means of electron beam (EBL) and use of reactive ions in plasma to etch it (ICP/RIE), mostly due to the capactive charging effects deflecting the beam and blurring the written pattern, which also suffers from the lack of adhesion to the most common lithographic resins.…”

“…Diamond is nevertheless an insulator, which makes it a challenging material to perform standard lithogrpahy by means of electron beam (EBL) and use of reactive ions in plasma to etch it (ICP/RIE), mostly due to the capactive charging effects deflecting the beam and blurring the written pattern, which also suffers from the lack of adhesion to the most common lithographic resins. These nanofabrication issues can be resolved by sophisticated use of decharging layers and dedicated plasma technology [12]. Other method to increase the photoluminescence count-rate and stability of NV − in diamond is the use of dedicated surface termination.…”

Plasma treatments and photonic nanostructures for shallow nitrogen vacancy centers in diamond

“…The novel fabrication process used here includes a SF 6 -based plasma to remove the silicon adhesion layer which could potentially attack HSQ masks [40]. We however find that this plasma etches our thin (25 nm) silicon adhesion layer 20 times faster than the HSQ mask and should not cause mask erosion and strong tapering [40]. We consequently suspect an additional effect causing the tapering.…”

“…We note that the investigated pillars have a stronger taper angle than we typically aim for [14]. The novel fabrication process used here includes a SF 6 -based plasma to remove the silicon adhesion layer which could potentially attack HSQ masks [40]. We however find that this plasma etches our thin (25 nm) silicon adhesion layer 20 times faster than the HSQ mask and should not cause mask erosion and strong tapering [40].…”