The detailed studies of the surface structure of synthetic boron-doped diamond single crystals using both conventional X-ray and synchrotron nano- and microbeam diffraction, as well as atomic force microscopy and micro-Raman spectroscopy, were carried out to clarify the recently discovered features in them. The arbitrary shaped islands towering above the (111) diamond surface are formed at the final stage of the crystal growth. Their lateral dimensions are from several to tens of microns and their height is from 0.5 to 3 μm. The highly nonequilibrium conditions of crystal growth enhance the boron solubility and, therefore, lead to an increase of the boron concentrations in the islands on the surface up to 10²² cm⁻³, eventually generating significant stresses in them. The stress in the islands is found to be the volumetric tensile stress. This conclusion is based on the stepwise shift of the diamond Raman peak toward lower frequencies from 1328 to 1300 cm⁻¹ in various islands and on the observation of the shift of three low-intensity reflections at 2-theta Bragg angles of 41.468°, 41.940° and 42.413° in the X-ray diffractogram to the left relative to the (111) diamond reflection at 2theta = 43.93°. We believe that the origin of the stepwise tensile stress is a discrete change in the distances between boron–carbon layers with the step of 6.18 Å. This supposition explains also the stepwise (step of 5 cm⁻¹) behavior of the diamond Raman peak shift. Two approaches based on the combined application of Raman scattering and X-ray diffraction data allowed determination of the values of stresses both in lateral and normal directions. The maximum tensile stress in the direction normal to the surface reaches 63.6 GPa, close to the fracture limit of diamond, equal to 90 GPa along the [111] crystallographic direction. The presented experimental results unambiguously confirm our previously proposed structural model of the boron-doped diamond containing two-dimensional boron–carbon nanosheets and bilayers.

使用常规X射线和同步加速器纳米和微束衍射以及原子力显微镜和显微拉曼光谱对合成硼掺杂的金刚石单晶的表面结构进行了详细研究，以阐明最近发现的特征在他们中。高耸在（111）金刚石表面上方的任意形状的岛在晶体生长的最后阶段形成。它们的横向尺寸为几微米到几十微米，高度为0.5到3微米。晶体生长的高度非平衡条件提高了硼的溶解度，因此导致表面岛中的硼浓度增加至10 ²²  cm ^-3，最终在其中产生很大的压力。发现岛中的应力为体积拉伸应力。该结论基于钻石拉曼峰在各个岛中从1328到1300 cm ^-1向较低频率的逐步位移，以及观察到在2θBragg角为41.468°，41.940时三个低强度反射的位移。相对于（111）金刚石在2θ= 43.93°处的反射，X射线衍射图中的0和42.413°位于左侧。我们认为，逐步拉伸应力的起源是硼-碳层之间距离的离散变化，其变化为6.18Å。此假设还解释了逐步（5 cm ^-1的步长）金刚石拉曼峰移动的行为。基于拉曼散射和X射线衍射数据的组合应用的两种方法可以确定横向和法向应力值。在垂直于表面的方向上的最大拉伸应力达到63.6 GPa，接近金刚石的断裂极限，沿着[111]结晶方向等于90 GPa。呈现的实验结果清楚地证实了我们先前提出的包含二维硼碳纳米片和双层硼掺杂金刚石的结构模型。