采用溶胶凝胶法制备不同Ce含量的Ce-Cu共掺杂SnO₂薄膜, 通过实验及第一性原理计算研究了掺杂对SnO₂微观结构及光电特性的影响. 结果表明, 掺杂后薄膜物相未发生较大变化, Cu, Ce均以替代Sn位形式掺入, 形成C{u}_{Sn}^{2+},C{e}_{Sn}^{3+}受主型缺陷. 随Ce掺杂浓度增加, 薄膜晶粒尺寸和光学带隙均减小, 电阻率先减小后增大, Ce掺杂量影响薄膜内陷阱分布从而导致电阻发生改变. PL光谱测试发现, SnO₂在390 nm处出现紫外发光峰, 主要与O空位有关, Ce³⁺的5d→4f跃迁在470 nm处产生蓝光发光峰, 且随掺杂浓度增加发光峰强度先增大后减小并发生红移. 第一性原理计算表明, Cu 3d态在价带顶上方产生受主能级, 而Ce掺杂后使导带整体下移, 光带隙减小, 进而提高导电性.

Tin dioxide (SnO₂) is a wide band gap semiconductor. SnO₂ has recently received a large interest because of its multiple technological applications, including solar cells, optoelectronic devices, flat panel displays, gas sensors, architectural windows and catalysts, owing to its good optical and electrical properties and excellent chemical and thermal stability. Compared to traditional materials which based on sulfur compound, rare earth elements doped oxides possess obvious advantages, such as good chemical stability, high transparency in the range of visible light, and nontoxic. In this work, the Ce-Cu codoping of SnO₂ thin films were prepared by sol-gel method. The influence of Ce-Cu codoping on the microstructural and optoelectrical properties has been investigated. Both Cu and Ce dopants are incorporated at substitutional sites (C{u}_{Sn}^{2+}, C{e}_{Sn}^{3+}), acting as the acceptors. With increasing the Ce content, the film grain size and optical band gap decrease, while the resistivity decreases at first and then increases due to the change of spatial trap distribution. The ultraviolet peak of the films can be attributed to the oxygen vacancies, while the blue emission at 470 nm belongs to the electron transition between 5d excited state and 4f state of Ce³⁺ ion. Besides, the intensity of the visible emission peak is influenced by the Ce content. The band structure, density of states of SnO₂, intrinsic and doped separately with Cu and Ce were investigated by first-principles full potential linearized augmented plane wave method. The Ce-Cu co-dopants make the conduction band shift down and induce a fully occupied impurity band above the valance band, and 4f orbital of Ce inserts into the conduction band, which leads the shift of the bottom of the conduction band to lower energy zone and narrowing of band gap, thus the band gap is decreased and the conductivity is improved.