Abstract
The epitaxial synthesis of high-quality 2D layered materials is an essential driver of both fundamental physics studies and technological applications. Bi2Se3, a prototypical 2D layered topological insulator, is sensitive to defects imparted during the growth, either thermodynamically or due to the film-substrate interaction. In this study, it is shown that step-terminated Al2O3 substrates with a high miscut angle (3°) can effectively suppress a particular hard-to-mitigate defect, the antiphase twin. Systematic investigations across a range of growth temperatures and substrate miscut angles confirm that atomic step edges act as preferential nucleation sites, stabilizing a single twin domain. First-principles calculations suggest that there is a significant energy barrier for twin boundary formation at step edges, supporting the experimental observations. Detailed structural characterization indicates that this twin-selectivity is lost through the mechanism of the 2D layers overgrowing the step edges, leading to higher twin density as the thickness increases. These findings highlight the complex energy landscape unique to 2D materials that is driven by the interplay between substrate properties, nucleation dynamics, and defect formation, and overcoming and controlling these are critical to improve material quality for quantum and electronic applications.
| Original language | English |
|---|---|
| Journal | Advanced Functional Materials |
| DOIs | |
| State | Accepted/In press - 2025 |
Funding
This work was supported by the U. S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division (Growth and X‐ray diffraction). The National Quantum Information Science Research Centers, Quantum Science Center, and the NNSA's Laboratory Directed Research and Development Program at Los Alamos National Laboratory (assistance in growth). Los Alamos National Laboratory is managed by Triad National Security, LLC for the U.S. Department of Energy's NNSA, under contract 89233218CNA00000 (Part of the X‐ray diffraction). Y.C. acknowledges the support from the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division through the Early Career Research Program (X‐ray diffraction analysis). The first principles calculations done at the University of Alabama at Birmingham were supported by the National Science Foundation under Grant No. OIA‐2229498, and the ORAU Ralph E. Powe Junior Faculty Enhancement Award. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a Department of Energy Office of Science User Facility using NERSC award CNMS2023‐A‐01934. The authors also gratefully acknowledge the resources provided by the University of Alabama at Birmingham IT‐Research Computing group for high performance computing (HPC) support and CPU time on the Cheaha compute cluster. G.A.V.‐L. and D.R.H. acknowledge support for electron microscopy through startup funds from the Penn State Eberly College of Science, Department of Chemistry, College of Earth and Mineral Sciences, Department of Materials Science and Engineering, and Materials Research Institute. G.A.V.‐L. and J.B. acknowledges support from the DOE Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education (ORISE) for the DOE. ORISE is managed by ORAU under contract number DE‐ SC0014664. This STEM specimens were prepared using Electron Microscopy Facility of the Center for Functional Nanomaterials (CFN), which is a U.S. Department of Energy Office of Science User Facility, at Brookhaven National Laboratory under Contract No. DE‐SC0012704, and the STEM and AFM experiments were conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory.
Keywords
- 2D materials
- molecular beam epitaxy
- quantum materials
- spintronics
- topological