Abstract
Epitaxial growth of complex oxides on large-area wafers, such as sapphire and silicon, represents a key step toward scalable oxide device production. Solid phase epitaxy allows the synthesis of γ-Al2O3 on α-Al2O3 and provides a template with a matched lattice constant and appropriate cubic symmetry for subsequent heteroepitaxial growth of perovskite complex oxides. Nb-doped SrTiO3 thin films were deposited epitaxially on (111)-oriented γ-Al2O3 intermediate layers on (0001) c-axis-oriented sapphire α-Al2O3 crystals using pulsed laser deposition. The Nb:SrTiO3 thin films with a thickness of 53 nm, grown at 700 °C on γ-Al2O3, reached fully relaxed lattice parameters and were epitaxially oriented with respect to the substrate. Nb:SrTiO3 layers deposited using identical deposition conditions directly on α-Al2O3, without the γ-Al2O3 intermediate layer, were polycrystalline. The sheet conductivity of Nb:SrTiO3 grown on γ-Al2O3/α-Al2O3 is more than ten times higher than that of Nb:SrTiO3 grown directly on α-Al2O3 without the γ-Al2O3 layer. The results point to new directions for the integration of (111)-oriented pseudocubic perovskite complex oxides and the integration of epitaxial complex oxides over larger areas using α-Al2O3 single-crystal substrates.
| Original language | English |
|---|---|
| Article number | 071124 |
| Journal | APL Materials |
| Volume | 13 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 1 2025 |
Funding
This research was primarily supported by the NSF Division of Materials Research through the University of Wisconsin Materials Research Science and Engineering Center (Grant No. DMR-1720415). The authors gratefully acknowledge the use of facilities and instrumentation in the Wisconsin Center for Nanocale Technology. The Center is partially supported by the Wisconsin Materials Research Science and Engineering (NSF DMR-2309000) and by the University of Wisconsin-Madison. D.V.C. acknowledges the support of the Novo Nordisk Foundation NERD program: New Exploratory Research and Discovery, Superior Grant No. NNF21OC0068015, and the support from the Independent Research Fund Denmark for the Sapere Aude Project Solid Grant No. 10.46540/3123-00034B. D.V.C. and C.N.L. further acknowledge the funding from the Independent Research Technology and Production Science, DFF Research 3 PILOT (Grant No. 00069B). Conductive atomic-force microscopy measurements were conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory.