Influence of point defects on the near edge structure of hexagonal boron nitride
Influence of point defects on the near edge structure of hexagonal boron nitride
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DOI：
10.1103/physrevb.96.144106
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发表时间：
2017-10-11
影响因子：
3.7
通讯作者：
McCulloch, Dougal G.
中科院分区：
文献类型：
--
作者：
McDougall, Nicholas L.;Partridge, Jim G.;McCulloch, Dougal G.
六方氮化硼 (hBN) 是一种宽带隙半导体，其应用包括石墨烯晶体管中的栅极绝缘层、远紫外发光器件和氢存储介质。由于其复杂的微观结构，六方氮化硼的缺陷很难识别。在这里，我们将 X 射线吸收近边缘结构 (XANES) 光谱与从头算理论模型相结合，以识别能量上有利的缺陷。在真空和氧气中对 hBN 样品进行退火后，B 和 N K 边缘表现出与面内缺陷一致的角度依赖性峰值修改。理论计算表明，能量上有利的缺陷都会在 XANES 中产生标志性特征。将这些计算与实验进行比较，主要缺陷归因于氮位点的替代氧、硼位点的替代碳以及氢钝化的硼空位。研究发现缺陷的氢钝化显着影响形成能、电子态和 XANES。在 B K 边缘，由于这些缺陷，出现了高于主 ls 到 pi* 峰的多个峰，并且氢钝化的硼空位在 is 到 sigma* 转变中产生了经常观察到的双峰。虽然 N K 边缘对缺陷不太敏感，但观察到了 B 位点替换 C 的特征。该缺陷还被计算为在其能带结构中具有中带隙态，这可能是从该材料中经常观察到的 4.1-eV 紫外线发射的原因。
Hexagonal boron nitride (hBN) is a wide-band-gap semiconductor with applications including gate insulation layers in graphene transistors, far -ultraviolet light emitting devices and as hydrogen storage media. Due to its complex microstructure, defects in hBN are challenging to identify. Here, we combine x-ray absorption near edge structure (XANES) spectroscopy with ab initio theoretical modeling to identify energetically favorable defects. Following annealing of hBN samples in vacuum and oxygen, the B and N K edges exhibited angular-dependent peak modifications consistent with in-plane defects. Theoretical calculations showed that the energetically favorable defects all produce signature features in XANES. Comparing these calculations with experiments, the principle defects were attributed to substitutional oxygen at the nitrogen site, substitutional carbon at the boron site, and hydrogen passivated boron vacancies. Hydrogen passivation of defects was found to significantly affect the formation energies, electronic states, and XANES. In the B K edge, multiple peaks above the major ls to pi* peak occur as a result of these defects and the hydrogen passivated boron vacancy produces the frequently observed doublet in the is to sigma* transition. While the N K edge is less sensitive to defects, features attributable to substitutional C at the B site were observed. This defect was also calculated to have mid-gap states in its band structure that may be responsible for the 4.1-eV ultraviolet emission frequently observed from this material.