The combination of atomic force microscopy and diamond nitrogen-vacancy (NV) center resulted in a versatile quantum sensing module with high sensitivity and high resolution¹⁾, enabled by the atomic-scale quantum spin sensor and its proximity to the sample under investigation. We have developed a simple method to fabricate diamond NV probes through laser cutting and Ga⁺ ion FIB milling²⁾. In this study, we investigated a post-fabrication treatment to recover its quantum spin coherence properties. To protect against detrimental effects caused by the Ga+ ions milling, an NV-hosting diamond is coated by polyvinyl alcohol and subsequent Pt-Pd coating prior to the fabrication. UV/ozone exposure to the diamond NV probe following the fabrication improves its surface condition by oxygen-termination, stabilizing the NV centers' charge state and diminishing noise-inducing surface radicals³⁾. The effectiveness of this post-fabrication treatment is indicated by the improvement of the NV coherence properties including 2-fold improvement of Rabi oscillation contrast, 10-fold Hahn echo T₂ improvement, and 2-fold longitudinal spin relaxation T₁ improvement. To demonstrate the ability of the diamond NV probe as a scanning magnetometer, we image the magnetic domain structure of a ferrimagnetic garnet (BiLu)₃Fe₅O₁₂, showing the ability to resolve a few hundred-nanometer magnetic domain wall structures.

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