Template-assisted bottom-up growth of nanocrystalline diamond micropillar arrays

Abstract

Micro-patterned diamond has been investigated for numerous applications, such as biomimetic surfaces, electrodes for cell stimulation and energy storage, photonic structures, imprint lithography, and others. Controlled patterning of diamond substrates and moulds typically requires lithography-based top-down processing, which is costly and complex. In this work, we introduce an alternative, cleanroom-free approach consisting of the bottom-up growth of nanocrystalline diamond (NCD) micropillar arrays by chemical vapour deposition (CVD) using a commercial porous Si membrane as a template. Conformal pillars of ~4.7 μm in height and ~2.2 μm in width were achieved after a maximum growth time of 9 h by hot-filament CVD (2% CH4 in H2, 725 °C at 10 mbar). In order to demonstrate one of many possible applications, micropillar arrays grown for 6 h, with ~2 μm in height, were evaluated as moulds for imprint lithography by replication onto hard cyclic olefin copolymer (COC) and onto soft polydimethylsiloxane (PDMS) elastomer. The results showed preserved mechanical integrity of the diamond moulds after replication, as well as full pattern transfer onto the two polymers, with matching dimensions between the grown pillars and the replicated holes. Prior surface treatment of the diamond mould was not required for releasing the PDMS replica, whereas the functionalisation of the diamond surface with a perfluorododecyltrichlorosilane (FDDTS) anti-stiction layer was necessary for the successful release of the COC replica from the mould. In summary, this paper presents an alternative and facile route for the fabrication of diamond micropillar arrays and functional micro-textured surfaces.