Controlling band alignments by artificial interface dipoles at perovskite heterointerfaces.

Takeaki Yajima,Masaharu Oshima,Christopher Bell,Hiroshi Kumigashira,Makoto Minohara,Harold Y. Hwang,David A. Muller,Julia A. Mundy,Yasuyuki Hikita,Lena F. Kourkoutis

doi:10.1038/ncomms7759

Abstract

The concept ‘the interface is the device' is embodied in a wide variety of interfacial electronic phenomena and associated applications in oxide materials, ranging from catalysts and clean energy systems to emerging multifunctional devices. Many device properties are defined by the band alignment, which is often influenced by interface dipoles. On the other hand, the ability to purposefully create and control interface dipoles is a relatively unexplored degree of freedom for perovskite oxides, which should be particularly effective for such ionic materials. Here we demonstrate tuning the band alignment in perovskite metal-semiconductor heterojunctions over a broad range of 1.7 eV. This is achieved by the insertion of positive or negative charges at the interface, and the resultant dipole formed by the induced screening charge. This approach can be broadly used in applications where decoupling the band alignment from the constituent work functions and electron affinities can enhance device functionality.

Highlights

The concept ‘the interface is the device’ is embodied in a wide variety of interfacial electronic phenomena and associated applications in oxide materials, ranging from catalysts and clean energy systems to emerging multifunctional devices
We demonstrate this design possibility using SrRuO3/Nb:SrTiO3 perovskite metal/semiconductor Schottky heterojunctions; they are an ideal starting point in that the experimentally measured Schottky barrier height (SBH) is accurately given by the energy difference between the SrRuO3 metal work function (F) and the Nb:SrTiO3 n-type semiconductor electron affinity (w)[12,13]
By using the artificial interface dipole, we control the SBH at the SrRuO3/ Nb:SrTiO3 Schottky junction over a broad range of 1.7 eV

Summary

Introduction

The concept ‘the interface is the device’ is embodied in a wide variety of interfacial electronic phenomena and associated applications in oxide materials, ranging from catalysts and clean energy systems to emerging multifunctional devices. We demonstrate tuning the band alignment in perovskite metal-semiconductor heterojunctions over a broad range of 1.7 eV This is achieved by the insertion of positive or negative charges at the interface, and the resultant dipole formed by the induced screening charge. Oxide interfaces are central constituents in clean energy research, such as in photocatalysis[5,6] and solar cells[7] In all of these fields, a common principle which defines the device properties is the band alignment. By using the artificial interface dipole, we control the SBH at the SrRuO3/ Nb:SrTiO3 Schottky junction over a broad range of 1.7 eV This level of control, representing a change of B50% of the oxide semiconductor band gap, provides a compelling toolbox for oxide materials in a wide range of applications

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Conclusion