含硅空位（SiV）色心的纳米金刚石在高温高压退火下的纳米级石墨化与缺陷演化
Nanoscale graphitization and defect evolution in silicon-vacancy center-containing nanodiamonds under high-pressure high-temperature annealing
AI总结：
该研究通过原位同步辐射X射线衍射确定了含SiV色心的纳米金刚石高温高压退火的石墨化阈值，建立了规避石墨化的工艺窗口，改善了其光学响应以用于量子技术。
AI中文摘要：
硅空位（SiV）缺陷等IV族色心是固态量子技术的极具潜力的候选材料。然而，纳米金刚石通常存在显著的晶格应变与结构无序，这会降低其光学性能，并阻碍低温下精细光谱结构的分辨。高温高压（HPHT）退火为弛豫内部应变提供了潜在途径，但纳米尺度金刚石在这类条件下的相稳定性仍未得到充分约束。本研究利用SOLEIL同步辐射装置的Paris-Edinburgh压机结合原位X射线衍射，探究纳米金刚石在HPHT退火过程中的结构演化。专用的纳米金刚石-NaCl-Pt样品组件实现了精准的压力-温度校准与相变的实时监测。衍射数据显示，在施加的HPHT加热方案下，金刚石向石墨的转变起始于2 GPa下约1800 K、4 GPa下约2120 K。这些实验确定的石墨化起始点定义了纳米金刚石HPHT退火的实用压力-温度工艺窗口，可避免可检测到的石墨化，并为可靠的非束流退火处理提供了校准框架，从而规避石墨化。对退火温度低于石墨化阈值的样品进行光致发光测量，结果显示其光学响应得到改善，在12 K下可部分分辨SiV的精细结构。这些光学测量表明，纳米金刚石的相稳定性与含SiV的单个纳米金刚石经HPHT退火后的光学响应存在关联。实验确立的HPHT工艺窗口为量子纳米金刚石的可控加工提供了实用框架，同时避免石墨化。
英文摘要：
Group-IV color centers, such as the silicon-vacancy (SiV) defect, are highly promising for solid-state quantum technologies. However, nanodiamonds typically exhibit significant lattice strain and structural disorder, which degrade their optical properties and hinder the resolution of the fine spectral structure at cryogenic temperatures. High-pressure high-temperature (HPHT) annealing offers a potential route to relax internal strain, although the phase stability of diamond at the nanoscale under such conditions remains poorly constrained. Here, we investigate the structural evolution of nanodiamonds during HPHT annealing using a Paris-Edinburgh press coupled with in situ synchrotron X-ray diffraction at SOLEIL. A dedicated sample assembly combining nanodiamonds - NaCl - Pt enabled accurate pressure-temperature calibration and real-time monitoring of phase transformations. The diffraction data reveal that the onset of diamond-to-graphite transition occurs at approximately 1800 K at 2 GPa and 2120 K at 4 GPa under the applied HPHT heating protocol. These experimentally determined graphitization onsets define a practical pressure-temperature processing window for HPHT annealing of nanodiamonds while avoiding detectable graphitization and provide a calibrated framework for reliable off-beam annealing treatments that avoid graphitization. Photoluminescence measurements on samples annealed below the graphitization threshold show improved optical response, with partial resolution of the SiV fine structure at 12 K. These optical measurements suggest a relationship between nanoscale phase stability and the optical response of individual SiV-containing nanodiamonds following HPHT annealing. The experimentally established HPHT processing window provides a practical framework for the controlled processing of quantum nanodiamonds while avoiding graphitization.
