Wide range bandgap modulation in strained SrSnO3 epitaxial films
Wide range bandgap modulation in strained SrSnO3 epitaxial films
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DOI：
10.1039/c9tc06211d
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发表时间：
2020-03
影响因子：
6.4
通讯作者：
Q. Gao;Kaifeng Li;L. Zhao;Kai Lv;Hong Li;Jinfeng Zhang;Wenhan Du;Qinzhuang Liu
中科院分区：
文献类型：
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作者：
Q. Gao;Kaifeng Li;L. Zhao;Kai Lv;Hong Li;Jinfeng Zhang;Wenhan Du;Qinzhuang Liu
通过实验和密度泛函理论 (DFT) 模拟方法研究了脉冲激光沉积在 (001) 取向 LaAlO3 (LAO) 和 MgO 衬底上外延生长的 SrSnO3 (SSO) 薄膜的结构和带隙的应变效应。高分辨率X射线衍射分析表明，随着膜厚度的减小，LAO(001)和MgO(001)基底上的SSO薄膜的面内(IP)双轴压缩和拉伸应变分别逐渐增加。通过光学透射率测量，随着膜厚度的减小，LAO 基底上的 SSO 薄膜的光学带隙从 4.44 eV 增加到 5.59 eV，MgO 基底上的 SSO 薄膜的光学带隙从 4.57 eV 增加到 5.61 eV。利用X射线光电子能谱测量SSO薄膜的表面化学态，发现IP拉伸应变的增加会增加氧空位（VO）的浓度。基于DFT的计算表明，IP压缩应变将Sn 5s轨道提升到更高的能级，IP拉伸应变导致价带降低，从而加宽了带隙，这与我们的实验结果一致。这些结果表明，具有宽范围带隙调谐的应变SSO外延膜可能在场效应晶体管和太阳能电池中具有潜在的应用。
Strain effects on the structure and bandgap of SrSnO3 (SSO) films epitaxially grown on (001)-orientation LaAlO3 (LAO) and MgO substrates by pulsed laser deposition were investigated via experiment and density functional theory (DFT) simulation approaches. High-resolution X-ray diffraction analysis revealed that in-plane (IP) biaxial compressive and tensile strains increase gradually for SSO films on LAO(001) and MgO(001) substrates with decreasing film thickness, respectively. The optical bandgaps of SSO films increase from 4.44 to 5.59 eV on LAO substrates and from 4.57 to 5.61 eV on MgO substrates with a decrease in the film thickness, which were measured by optical transmittances. X-ray photoelectron spectroscopy was used to measure the surface chemical states of SSO films and it was found that the increase of IP tensile strain would increase the concentration of oxygen vacancies (VOs). Calculations based on DFT showed that IP compressive strain lifts the Sn 5s orbitals to a higher energy level, and IP tensile strain results in lowering of the valence band, thereby widening the bandgap which are consistent with our experimental results. These results suggest that the strained SSO epitaxial films possessing a wide range bandgap tuning may have potential applications in field effect transistors and solar cells.