Probing the growth quality of molecular beam epitaxy-grown Bi2Se3 films via in-situ spectroscopic ellipsometry
Probing the growth quality of molecular beam epitaxy-grown Bi2Se3 films via in-situ spectroscopic ellipsometry
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DOI：
10.1016/j.jcrysgro.2022.126714
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发表时间：
2022-05-20
影响因子：
1.8
通讯作者：
Peiris, Frank
中科院分区：
文献类型：
--
作者：
Bai, Aofeng;Hilse, Maria;Peiris, Frank
采用分子束外延法生长了拓扑绝缘体Bi2Se3和传统半导体In2Se3的多层异质结构，以及（Bi1-xInx）(2) SE -3层的固溶体层，并利用椭圆偏振光谱（SE）分析了其运行状态。在每一层沉积后获得SE谱，以确定每一层的介电函数和厚度。在非原位SE中，介电函数和各层厚度的不确定性限制了从单组SE数据中提取多层异质结构介电函数的正确模型，而逐步原位SE数据恢复了更精确的Bi2Se3， In2Se3, (Bi0.7In (0.3))(2) SE -3和帽层的介电函数。为多层结构建立的光学模型可以解释层中随生长过程而发生的微小扰动。我们的模型表明，在600℃退火时，生长在蓝宝石衬底旁边的~ 7 nm Bi2Se3层似乎消失了。最后，当介电函数表示为kramers - kronigi -consistent振荡器的集合时，原位SE预测了薄膜的质量；在（Bi0.7In (0.3)）(2)Se-3层上生长的Bi2Se3薄膜所用振荡器的加权平均展宽参数比直接在蓝宝石上生长的Bi2Se3薄膜小20%，证实了前者薄膜的质量更好，并为量化薄膜质量和缺陷浓度提供了直接指标。这些结论得到了运输数据的证实。
Multilayer heterostructures of the topological insulator Bi2Se3 and conventional semiconductor In2Se3, as well as solid solution layers of (Bi1-xInx)(2)Se-3 layers were grown by molecular beam epitaxy and analyzed in-operando using spectroscopic ellipsometry (SE). SE spectra were obtained after the deposition of each layer to deter-mine the respective dielectric functions and thicknesses of each layer. In contrast to ex-situ SE, where uncertainty in the dielectric function and thicknesses of individual layer impose limitations to extract a correct model for the dielectric function of such multilayer heterostructures from a single set of SE data, the step-by-step in-situ SE data recover more precise dielectric functions for Bi2Se3, In2Se3, (Bi0.7In (0.3))(2)Se-3 and the cap-layer. The optical models developed for multilayer structures can decipher minute perturbations in layers as the growth progresses. Our models show that a ~ 7 nm Bi2Se3 layer grown next to a sapphire substrate seems to disappear as the structure is annealed at 600 C. Finally, when the dielectric functions were represented as a collection of Kramers-Kronig-consistent oscillators, in-situ SE predicted the quality of films; the weighted-average broadening parameter for oscillators used for Bi2Se3 films grown on (Bi0.7In (0.3))(2)Se-3 layer is-20% smaller compared to Bi2Se3 films directly grown on sapphire, confirming that the former film is of better quality, and providing a direct metric to quantify film quality and defect concentration. These conclusions were corroborated by transport data.