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Title: Epitaxial Growth and Band Alignment of p-NiO/n-Fe2O3 Heterojunction on Al2O3(0001)

Abstract

Fe2O3 is one of the promising oxide semiconductors as photoanodes for photoelectrochemical water splitting, but its efficiency is still limited by the short diffusion length of photo-excited carriers. Using the internal electric field formed at a p-n heterojunction (HJ) is an efficient strategy to mitigate such limitation. Accordingly, the interfacial atomic structure and band alignment are the most crucial parameters for efficiency optimization. In this work, we report on the epitaxial growth and determination of the band energy alignment of NiO/Fe2O3 p-n heterojunction grown on Al2O3(0001) substrate by pulsed laser deposition. We show that high crystalline quality NiO(111) thin films can be grown on Fe2O3(0001) with epitaxial relationships of [1 ¯11]NiO||[0001 ¯ ]Fe2O3(out-of-plane), [1 ¯1 ¯0]NiO||[011 ¯0]Fe2O3 and [1 ¯12 ¯ ]NiO||[21 ¯1 ¯0]Fe2O3(in-plane). The rotation of NiO hexagons by 30° can effectively reduce the lattice mismatch from ~17.4% to ~1.58%. High resolution X-ray photoelectron spectroscopy reveals that valence and conduction band offset of NiO/Fe2O3 heterojunction are 0.7 eV and 2.3 eV with an upward band bending potential of 0.23 eV for Fe2O3 and a downward band bending potential of 0.32 eV for NiO, respectively. This kind of interfacial band alignment not only facilitates the charge separation, but lowers themore » overpotentials for oxygen evolution reaction.« less

Authors:
 [1];  [2];  [1];  [1];  [1];  [1]; ORCiD logo [2];  [1]
  1. Xiamen University
  2. BATTELLE (PACIFIC NW LAB)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1548268
Report Number(s):
PNNL-SA-138270
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Applied Surface Science
Additional Journal Information:
Journal Volume: 464
Country of Publication:
United States
Language:
English
Subject:
Photoelectrochemical Water Splitting, Oxide Semiconductor, Heterojunction, Electronic Structure, Band Offset, Fe2O3

Citation Formats

Qin, Yixi, Yang, Zhenzhong, Wang, J J., Xie, Z Y., Cui, Meiyan, Tian, C M., Du, Yingge, and Zhang, Kelvin H. Epitaxial Growth and Band Alignment of p-NiO/n-Fe2O3 Heterojunction on Al2O3(0001). United States: N. p., 2019. Web. doi:10.1016/j.apsusc.2018.09.106.
Qin, Yixi, Yang, Zhenzhong, Wang, J J., Xie, Z Y., Cui, Meiyan, Tian, C M., Du, Yingge, & Zhang, Kelvin H. Epitaxial Growth and Band Alignment of p-NiO/n-Fe2O3 Heterojunction on Al2O3(0001). United States. doi:10.1016/j.apsusc.2018.09.106.
Qin, Yixi, Yang, Zhenzhong, Wang, J J., Xie, Z Y., Cui, Meiyan, Tian, C M., Du, Yingge, and Zhang, Kelvin H. Tue . "Epitaxial Growth and Band Alignment of p-NiO/n-Fe2O3 Heterojunction on Al2O3(0001)". United States. doi:10.1016/j.apsusc.2018.09.106.
@article{osti_1548268,
title = {Epitaxial Growth and Band Alignment of p-NiO/n-Fe2O3 Heterojunction on Al2O3(0001)},
author = {Qin, Yixi and Yang, Zhenzhong and Wang, J J. and Xie, Z Y. and Cui, Meiyan and Tian, C M. and Du, Yingge and Zhang, Kelvin H.},
abstractNote = {Fe2O3 is one of the promising oxide semiconductors as photoanodes for photoelectrochemical water splitting, but its efficiency is still limited by the short diffusion length of photo-excited carriers. Using the internal electric field formed at a p-n heterojunction (HJ) is an efficient strategy to mitigate such limitation. Accordingly, the interfacial atomic structure and band alignment are the most crucial parameters for efficiency optimization. In this work, we report on the epitaxial growth and determination of the band energy alignment of NiO/Fe2O3 p-n heterojunction grown on Al2O3(0001) substrate by pulsed laser deposition. We show that high crystalline quality NiO(111) thin films can be grown on Fe2O3(0001) with epitaxial relationships of [1 ¯11]NiO||[0001 ¯ ]Fe2O3(out-of-plane), [1 ¯1 ¯0]NiO||[011 ¯0]Fe2O3 and [1 ¯12 ¯ ]NiO||[21 ¯1 ¯0]Fe2O3(in-plane). The rotation of NiO hexagons by 30° can effectively reduce the lattice mismatch from ~17.4% to ~1.58%. High resolution X-ray photoelectron spectroscopy reveals that valence and conduction band offset of NiO/Fe2O3 heterojunction are 0.7 eV and 2.3 eV with an upward band bending potential of 0.23 eV for Fe2O3 and a downward band bending potential of 0.32 eV for NiO, respectively. This kind of interfacial band alignment not only facilitates the charge separation, but lowers the overpotentials for oxygen evolution reaction.},
doi = {10.1016/j.apsusc.2018.09.106},
journal = {Applied Surface Science},
number = ,
volume = 464,
place = {United States},
year = {2019},
month = {1}
}