Quantum technologies based on quantum point defects in crystals require control over the defect charge state. Here we tune the charge state of shallow nitrogen-vacancy and silicon-vacancy centers by locally oxidizing a hydrogenated surface with moderate optical excitation and simultaneous spectral monitoring. The loss of conductivity and change in work function due to oxidation are measured in atmosphere using conductive atomic force microscopy and Kelvin probe force microscopy (KPFM). We correlate these scanning probe measurements with optical spectroscopy of the nitrogen-vacancy and silicon-vacancy centers created via implantation 15–25 nm beneath the diamond surface and annealing. The observed charge state of the defects as a function of optical exposure demonstrates that laser oxidation provides a way to precisely tune the Fermi level over a range of at least 2.00 eV. We also observe a significantly larger oxidation rate for implanted surfaces compared to unimplanted surfaces under ambient conditions. Combined with knowledge of the electron affinity of a surface, these results suggest KPFM is a powerful, high-spatial-resolution technique to advance surface Fermi level engineering for charge stabilization of quantum defects.

中文翻译：

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通过相关扫描探针显微镜和量子缺陷光谱测量金刚石费米能级的光学调谐

基于晶体中量子点缺陷的量子技术需要控制缺陷电荷态。在这里，我们通过适度的光学激发和同时光谱监测局部氧化氢化表面来调整浅氮空位和硅空位中心的电荷状态。使用传导原子力显微镜和开尔文探针力显微镜 (KPFM) 在大气中测量由于氧化导致的电导率损失和功函数变化。我们将这些扫描探针测量结果与通过注入金刚石表面下方 15-25 nm 并退火产生的氮空位和硅空位中心的光谱相关联。观察到的缺陷电荷态与光学曝光的函数关系表明，激光氧化提供了一种在至少 2.00 eV 范围内精确调节费米能级的方法。我们还观察到，在环境条件下，与未植入表面相比，植入表面的氧化率明显更高。结合表面电子亲和力的知识，这些结果表明 KPFM 是一种强大的高空间分辨率技术，可推进表面费米能级工程以实现量子缺陷的电荷稳定。