Abstract
High quality, ultra-thin single crystal diamond (SCD) membranes that have a thickness in the sub-micron range are of extreme importance as a materials platform for photonics, quantum sensing, nano/micro electro-mechanical systems (N/MEMS) and other diverse applications. However, the scalable fabrication of such thin SCD membranes is a challenging process. In this paper, we demonstrate a new method which enables high quality, large size (∼4 × 4 mm) and low surface roughness, low strain, ultra-thin SCD membranes which can be fabricated without deformations such as breakage, bowing or bending. These membranes are easy to handle making them particularly suitable for fabrication of optical and mechanical devices. We demonstrate arrays of single crystal diamond membrane windows (SCDMW), each up to 1 × 1 mm in dimension and as thin as ∼300 nm, supported by a diamond frame as thick as ∼150 μm. The fabrication method is robust, reproducible, scalable and cost effective. Microwave plasma chemical vapour deposition is used for in situ creation of single nitrogen-vacancy (NV) centers into the thin SCDMW. We have also developed SCD drum head mechanical resonator composed of our fully clamped and freely suspended membranes.
Highlights
Diamond is well-known for its exceptional mechanical, thermal and optical properties
Type Ib (4 × 4 × 0.5 mm) original high pressure high temperature (HPHT) single crystal diamond (SCD) substrate was used to fabricate 4 × 4 mm large membrane (Fig. 2a) and Type IIa (3 × 3 × 0.3 mm) CVD pristine substrate was diced into 1.5 × 1.5 mm 6862 | Nanoscale, 2016, 8, 6860–6865
Features like pyramids or pits in the membrane windows are observed for some samples, which are transferred from original substrates during CVD overgrowth step
Summary
Diamond is well-known for its exceptional mechanical, thermal and optical properties. A different method that has been used is the fabrication of 10 μm wide and millimetre long beams with 200 nm thickness by etching 10 μm deep trenches on a bulk SCD using RIE.[17,18] In the last step, thin strips are picked up mechanically from the substrate These membranes have not been used for integrated devices fabrication due to size limitations. The membrane properties are dependent primarily on control of the CVD overgrowth process, which has been shown to produce extremely high quality single crystal material provided sufficient substrate preparation methods are followed to minimize dislocation generation.[24] this fabrication process is suitable for large scale production, by allowing for parallel implantation, overgrowth and etching of multiple membranes
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