Colour centres in silicon carbide emerge as a promising semiconductor quantum technology platform with excellent spin-optical coherences. However, recent efforts towards maximising the photonic efficiency via integration into nanophotonic structures proved to be challenging due to reduced spectral stabilities. Here, we provide a large-scale systematic investigation on silicon vacancy centres in thin silicon carbide membranes with thicknesses down to 0.25 μm. Our membrane fabrication process involves a combination of chemical mechanical polishing, reactive ion etching, and subsequent annealing. This leads to highly reproducible membranes with roughness values of 3–4 Å, as well as negligible surface fluorescence. We find that silicon vacancy centres show close-to lifetime limited optical linewidths with almost no signs of spectral wandering down to membrane thicknesses of ~0.7 μm. For silicon vacancy centres in thinner membranes down to 0.25 μm, we observe spectral wandering, however, optical linewidths remain below 200 MHz, which is compatible with spin-selective excitation schemes. Our work clearly shows that silicon vacancy centres can be integrated into sub-micron silicon carbide membranes, which opens the avenue towards obtaining the necessary improvements in photon extraction efficiency based on nanophotonic structuring.

碳化硅中的色心成为一种有前途的半导体量子技术平台，具有出色的自旋光学相干性。然而，由于光谱稳定性降低，最近通过集成到纳米光子结构中来最大化光子效率的努力被证明具有挑战性。在这里，我们对厚度低至 0.25 μm 的碳化硅薄膜中的硅空位中心进行了大规模的系统研究。我们的膜制造工艺涉及化学机械抛光、反应离子蚀刻和后续退火的组合。这使得膜具有高度重复性，粗糙度值为 3-4 Å，并且表面荧光可以忽略不计。我们发现硅空位中心表现出接近寿命限制的光学线宽，几乎没有光谱漂移到约 0.7 μm 膜厚度的迹象。对于低至 0.25 μm 的更薄薄膜中的硅空位中心，我们观察到光谱漂移，但光学线宽仍低于 200 MHz，这与自旋选择性激发方案兼容。我们的工作清楚地表明，硅空位中心可以集成到亚微米碳化硅膜中，这为基于纳米光子结构的光子提取效率获得必要的改进开辟了道路。