Electronic Structure and Band Alignment at the NiO and SrTiO3 p–n Heterojunctions

5 years ago

Electronic Structure and Band Alignment at the NiO and SrTiO3 p–n Heterojunctions

Judith L. MacManus-Driscoll, Vlado K. Lazarov, Liang Qiao, Mark G. Blamire, David J. Payne, Rui Wu, Weiwei Li, Fengzai Tang, Kelvin H. L. Zhang, Freddy E. Oropeza, Yingge Du

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 SrTiO₃ (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 × 10³ 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.

Publisher URL: http://dx.doi.org/10.1021/acsami.7b06025

DOI: 10.1021/acsami.7b06025