Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K.
Department of Materials, Imperial College London , Exhibition Road, London SW7 2AZ, U.K.
ACS Appl Mater Interfaces. 2017 Aug 9;9(31):26549-26555. doi: 10.1021/acsami.7b06025. Epub 2017 Jul 25.
Understanding the energetics at the interface, including the alignment of valence and conduction bands, built-in potentials, and ionic and electronic reconstructions, is an important challenge in designing oxide interfaces that have controllable multifunctionalities for novel (opto-)electronic devices. In this work, we report detailed investigations on the heterointerface of wide-band-gap p-type NiO and n-type SrTiO (STO). We show that despite a large lattice mismatch (∼7%) and dissimilar crystal structure, high-quality NiO and Li-doped NiO (LNO) thin films can be epitaxially grown on STO(001) substrates through a domain-matching epitaxy mechanism. X-ray photoelectron spectroscopy studies indicate that NiO/STO heterojunctions form a type II "staggered" band alignment. In addition, a large built-in potential of up to 0.97 eV was observed at the interface of LNO and Nb-doped STO (NbSTO). The LNO/NbSTO p-n heterojunctions exhibit not only a large rectification ratio of 2 × 10 but also a large ideality factor of 4.3. The NiO/STO p-n heterojunctions have important implications for applications in photocatalysis and photodetectors as the interface provides favorable energetics for facile separation and transport of photogenerated electrons and holes.
理解界面的能量学，包括价带和导带的对准、内置电势、离子和电子重构，是设计具有可控多功能性的新型（光电）电子器件的氧化物界面的重要挑战。在这项工作中，我们报告了宽带隙 p 型 NiO 和 n 型 SrTiO（STO）异质界面的详细研究。我们表明，尽管存在较大的晶格失配（~7%）和不同的晶体结构，但通过畴匹配外延机制，高质量的 NiO 和 Li 掺杂 NiO（LNO）薄膜可以在 STO(001)衬底上外延生长。X 射线光电子能谱研究表明，NiO/STO 异质结形成了 II 型“交错”能带排列。此外，在 LNO 和 Nb 掺杂 STO（NbSTO）的界面观察到高达 0.97eV 的大内置电势。LNO/NbSTO p-n 异质结不仅表现出高达 2×10 的大整流比，而且还表现出高达 4.3 的大理想因子。NiO/STO p-n 异质结在光催化和光电探测器中的应用具有重要意义，因为界面为光生电子和空穴的易于分离和输运提供了有利的能量学。
