ZnO/ZnS大面积单晶异质结及其光电性能研究

Large-area Single-crystalline ZnO/ZnS Heterostructure and Its Optoelectronic Properties

ZnO和ZnS是重要的Ⅱ-Ⅵ族宽禁带半导体材料,二者之间形成的异质结具有Ⅱ型能带结构,可以促使受激载流子实现空间分离,延长受激载流子的寿命,从而提高材料的光催化和光电探测性能。本文利用物理气相沉积方法,首次在ZnO块状单晶衬底上生长了一层ZnS单晶薄膜,薄膜由厚约4nm、边长几百纳米,取向一致的等边三角形纳米片组成。X射线衍射和透射电子显微镜的表征结果显示,ZnS薄膜与ZnO衬底具有单一外延取向关系。阴极射线荧光光谱表明ZnS薄膜的制备显著提高了ZnO单晶片可见光荧光发光峰的强度。此外,对ZnO/ZnS异质结的紫外光电探测性能的研究结果显示,异质结对不同波长的紫外光均有响应,光响应的上升弛豫时间和下降弛豫时间分别为200ms和1050ms,展示了较好的光电应用潜力。

ZnO and ZnS are both important Ⅱ-Ⅵ wide bandgap semiconductors.Their heterostructures have Type-Ⅱ band alignment,which contributes to better charge separation efficiencies and longer charge lifetimes.In this work,a simple physical vapor deposition method was used to grow ZnS single-crystalline membrane on ZnO bulk substrates.The ZnS film was composed of ultrathin 4nm-thick equilateral ZnS triangles.This is the first report of synthesis of two-dimensional ultra-thin ZnS materials.XRD and TEM results reveal the epitaxial growth behavior of ZnS on ZnO substrates.After ZnS coating,the intensities of visible photoluminescence peak increased dramatically,which can be attributed to the defects introduced during the growth.An ultraviolet photodetector was assembled using the heterostructure,and its photodetection properties were evaluated.The results showed that the heterostructure can detect ultraviolet light of broad range of wavelengths,and the rising time and the decay time were 200 ms and 1050 ms,respectively,indicating that ZnO/ZnS large-area singlecrystalline heterostructuresare promising candidates for optoelectronic applications.