Sharp Diamond Needles for Single‐Photon Emission

Single‐crystal diamond needles (SCDNs) have emerged as promising candidates for optical and quantum sensing applications due to their unique shape, high‐quality crystalline structure, and availability for relatively simple mass production. In this study, morphology modification and luminescence features of SCDNs subjected to high‐temperature oxidation in air at 650 °C and 700 °C are investigated. Significant morphological changes, including sharpening, length reduction, and surface feature formation, are revealed as a result of oxidation with scanning electron microscopy observations. The morphology modifications are dependent on oxidation temperature. Gradual sharpening and formation of surface protrusions with (100) and (111) surfaces during oxidation at 650 °C significantly accelerate at oxidation temperature increase to 700 °C. Observed formation of the surface protrusions is explained by local variation in resistance to oxidation at diamond needle surface. Furthermore, photon correlation measurements reveal that oxidation duration may be optimized allowing obtaining of SCDNs with single nitrogen‐vacancy centers situated in their tips, and confirming the viability of these diamonds for quantum sensing. This findings highlight the superior optical properties and structural integrity of SCDNs, making them highly suitable for single‐photon emission and other quantum technological applications.