Self-regulated growth of [111]-oriented perovskite oxide films using hybrid molecular beam epitaxy

Joseph Roth,Roman Engel-Herbert,Alexej Pogrebnyakov,Tatiana Kuznetsova,Leixin Miao,Nasim Alem

doi:10.1063/5.0040047

Joseph Roth, Roman Engel-Herbert + Show 4 more

Open Access

https://doi.org/10.1063/5.0040047

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Journal: APL Materials	Publication Date: Feb 1, 2021
Citations: 4	License type: cc-by

Affiliation: Pennsylvania State University

Abstract

Exotic material properties and topological nontrivial surface states have been theoretically predicted to emerge in [111]-oriented perovskite layers. The realization of such [111]-oriented perovskite superlattices has been found challenging, and even the growth of perovskite oxide films along this crystallographic direction has been proven as a formidable task, attributed to the highly polar character of the perovskite (111) surface. Successful epitaxial growth along this direction has so far been limited to thin film deposition techniques involving a relatively high kinetic energy, specifically pulsed laser deposition and sputtering. Here, we report on the self-regulated growth of [111]-oriented high-quality SrVO3 by hybrid molecular beam epitaxy. The favorable growth kinetics available for the growth of perovskite oxides by hybrid molecular beam epitaxy on non-polar surfaces was also present for the growth of [111]-oriented films, resulting in high-quality SrVO3(111) thin films with residual resistivity ratios exceeding 20. The ability to grow high-quality perovskite oxides along energetically unfavorable crystallographic directions using hybrid molecular beam epitaxy opens up opportunities to study the transport properties of topological nontrivial and correlated electron systems.

Highlights

The growth of perovskite oxides has long been focused on [001]-oriented films due to the low surface energy of the {001} facets and the inherent stability of the growth front
High energy growth techniques operating far from thermodynamic equilibrium were required to overcome the effects of this high energy surface and achieve atomically smooth surfaces, such as pulsed laser deposition (PLD), which has been used for the growth of SrRuO3,14–16 SrFeO3,17 La0.7Sr0.3MnO3,18 AlFeO3,19 NdNiO3,20 SrIrO3,21 LaFeO3,22 BaTiO3,22 LaAlO3,23 PbTiO3,24
Thin films of SrVO3(111) were grown using a DCA M600 hybrid MBE (hMBE) equipped with a Sr thermal effusion cell and a molecular oxygen plasma source

Summary

INTRODUCTION

The growth of perovskite oxides has long been focused on [001]-oriented films due to the low surface energy of the {001} facets and the inherent stability of the growth front. The situation for the growth of [111]-oriented perovskites is similar, and it is hypothesized that agents aiding in the charge reduction of the interface are beneficial to the growth This effect might be achieved through the use of other chemical groups such as polar ligands liberated by the thermolysis of the metalorganic precursors used in hybrid MBE (hMBE), enabling the growth of perovskites along highly polar directions with high crystalline quality. This hypothesis has been tested for the heteroepitaxial growth of the correlated metal SrVO3, which has been extensively studied recently due to its potential use as a transparent electrode material.. The RRR value of 21 for hMBE grown films significantly exceeded the RRR quality metric of previously grown [111]-oriented SrVO3 by a factor of 4

RESULTS AND DISCUSSION

CONCLUSION

SrVO3 film synthesis

SrVO3 thin film characterization

Structural characterization