Fabrication of Diamond Nanoneedle Arrays Containing High‐Brightness Silicon‐Vacancy Centers

Abstract The optically active silicon‐vacancy (SiV) center in diamonds is an excellent candidate for quantum photonics and sensing applications. To date, optimizing the photoluminescence (PL) collection efficiency of SiV centers has proven difficult. To address this issue, the current study presents a simple two‐step method for preparing single‐crystalline diamond nanoneedle arrays. In the first step, silicon‐doped (001) textured diamond films are deposited with a mixture of microcrystalline and nanocrystalline grains in a microwave plasma CVD (MPCVD) system, using tetramethylsilane (TMS) gas as the dopant source. Subsequently, air annealing is used to selectively etch nanocrystalline diamond and sp² amorphous carbon phases, while retaining the [001]‐oriented diamond nanoneedles with a curved top surface. In comparison to the as‐deposited films, the PL emission of SiV centers in these diamond nanoneedles is enhanced by a factor of up to 12.1. The finite‐difference time‐domain simulations further demonstrate that removing the nanocrystalline diamond and sp² carbon from the sidewall of the diamond nanoneedles results in a remarkable increase in photoluminescence collection. Therefore, the findings have established for the first time the constraint effect of sp² carbon on the optical collection of color centers at the sidewall rather than the top surface.