AFM and Optical Studies of Boron Nitride and Graphene Grown By High Temperature Molecular Beam Epitaxy

六方氮化硼（hBN）可以用作其他二维材料（如石墨烯）上的绝缘阻挡层，也可以用作具有6 eV带隙的半导体。在大多数研究中，hBN是用胶带从块状晶体上剥离并转移到其他衬底上的。近年来，我们一直在研究高温分子外延生长六方氮化硼和石墨烯。目的是以一种可扩展的方式生长hBN，以允许生长hBN和石墨烯（例如）的受控异质结构。目前我们的重点是了解碳等掺杂原子是如何被掺入六方氮化硼中并影响层的生长的。利用原子分辨率原子力显微镜（AFM）、椭偏光谱和共聚焦荧光显微镜研究了这些层的结构和光学响应。例如，在低碳掺杂下，我们已经确定了先前提出的与碳杂质[3]有关的单光子发射器，在高碳掺杂下，我们可以在光谱椭偏特征中看到杂质带的形成。我们还与几个国际小组合作[例如参考文献1和3]进行额外的测量，例如深紫外荧光研究。该项目的博士生将负责使用高分辨率环境AFM，共聚焦显微镜和光谱椭偏仪对样品进行测量和分析。对于共聚焦显微镜实验，还有进一步发展仪器和研究其他类型缺陷的空间，例如硼空位，它们看起来非常稳定，可以作为单光子发射器，并且是局部感应磁场的候选材料。参考文献1。C. Elias等，（2019）自然通讯10,26392。赵彦杰等，（2016）科学报告6,344743。N. Mendelson等，（2021）Nature Materials 20, 3214。H.L. Stern等，（2022）《自然通讯》13,618

Hexagonal boron nitride (hBN) can be used as an insulating barrier layer on other 2D materials such as graphene or as a semiconductor with a 6 eV band gap [1]. In most research the hBN is exfoliated from bulk crystals using adhesive tape and transferred to other substrates. We have been investigating the growth of hexagonal boron nitride and graphene by high temperature molecular epitaxy for several years [2]. The aim is to grow hBN in a way that is scalable to allow controlled heterostructures of hBN and graphene (for instance) to be grown.At present our focus is on understanding how dopant atoms such as carbon are incorporated into the hexagonal boron nitride and affect the growth of the layers. We use atomic resolution atomic force microscopy (AFM), spectroscopic ellipsometry and confocal fluorescent microscopy to study the structure and optical response of the layers. For example, at low carbon doping we have identified single photon emitters that have previously been proposed as being related to carbon impurities [3] and at high carbon doping we can see the formation of impurity bands in the spectroscopic ellipsometry signatures. We also collaborate with several groups internationally [e.g. refs 1 and 3 ] to make additional measurements e.g. fluorescence study in the deep UV.The PhD student in this project will be responsible for measuring and analysing the samples using high resolution ambient AFM, confocal microscopy and spectroscopic ellipsometry. For the confocal microscopy experiments there is scope to further develop the instrumentation and to study other types of defects e.g. boron vacancies that appear to be very stable, can act as single photon emitters and are candidate materials for local sensing of magnetic fields [4].References1. C. Elias, et al, (2019) Nature Communications 10, 26392. Y.J. Cho, et al, (2016) Scientific Reports 6, 344743. N. Mendelson, et al, (2021) Nature Materials 20, 3214. H.L. Stern, et al, (2022) Nature Communications 13, 618