Tailoring physical functionalities of complex oxides by vertically aligned nanocomposite thin-film design

Jijie Huang,Judith L Macmanus-Driscoll,Hao Yang,Weiwei Li

doi:10.1557/s43577-021-00028-0

Abstract

Self-assembled nanocomposite thin films couple two materials into a single film, typically, in the form of vertically aligned nanopillars embedded in a matrix film. High-density vertical heterointerfaces provide a great platform for engineering new physical properties and novel multifunctionalities, as well as for nanoscale device integration. Tremendous research efforts have been devoted to developing different nanocomposite systems. In this article, we summarize recent progress on vertically aligned nanocomposite thin films for enhanced functionalities such as ferroelectricity, tunable magnetoresistance, multiferroicity, dielectricity, magnetic anisotropy, perpendicular exchange bias, novel electrical/ionic properties, interfacial conduction, and resistive switching. Using specific examples, we discuss how and why the fundamental physical properties can be significantly tuned/improved in vertically aligned nanocomposites. Finally, we propose future research directions to achieve further enhanced performance as well as practical devices.

Highlights

One of the leading technologies for future power generation Overall, the unique and easy-to-make nanostructure of vertiand for electrolysis is the solid-oxide fuel cell (SOFC) or cally aligned nanopillars embedded in an epitaxial matrix prosolid-oxide electrolytic cell (SOEC)
Strain engineering in 3D VANs75–77,135 the formation of anisotropic nanopillar geometries, as well could be applied much more widely to new systems to achieve as the high density of clean vertical heterointerfaces which physical property enhancements
There is much scope to explore nontering for oxide vertically aligned nanocomposite (VAN),[138,139] more work is still needed to demonstrate the universality of this and other large-area methods

Summary

Introduction

Complex oxide thin films have been integrated into semiconductor devices, and oxide thin films are of interest for many other wide-ranging electronic devices.[1,2,3,4,5] The physical properties of oxide thin films can be tailored by film-substrateinduced biaxial strain effect,[6,7,8,9,10] as well as doping effects.[11,12,13,14,15] Over the past decade, tremendous research efforts and studies have been devoted to the development of heteroepitaxial oxide nanocomposite thin films, which involve co-growth of two oxide materials into one solid thin film. VAN thin films present multiple advantages over conventional plain oxide thin films, owing to their unique threedimensional (3D) strain states, a large number of vertical heterointerfaces, and arising from the strong interplay of strain, spin, charge, and orbital orders both within the film and at interfaces.[16,17] In plain oxide thin films epitaxially grown on single-crystal substrates, the physical properties can be tuned by the lattice mismatch strain between the film and the substrate (in-plane biaxial strain). Multiferroics have been achieved in VANs with coupled ferroelectric and ferromagnetic phase, such as BaTiO3 (BTO):CoFe2O4 (CFO),[19] BFO:CFO,[20] and BTO:YMnO3.21 epitaxial growth of large lattice-mismatched or different crystal-structured VAN films can be realized by choosing an appropriate second phase.[22,23,24] new physical phenomenon or new phases can be induced by strain at the vertical heterointerface, which provides a great platform of new materials discovery.

B SBSBSB

Method I

Nb-doped SrTiO3 Substrate

Summary and future perspective