Abstract
BAs was predicted to have an unusually high thermal conductivity with a room temperature value of 2000 W m-1 K-1, comparable to that of diamond. However, the experimentally measured thermal conductivity of BAs single crystals is still lower than this value. To identify the origin of this large inconsistency, we investigate the lattice structure and potential defects in BAs single crystals at the atomic scale using aberration-corrected scanning transmission electron microscopy (STEM). Rather than finding a large concentration of As vacancies (VAs), as widely thought to dominate the thermal resistance in BAs, our STEM results show an enhanced intensity of some B columns and a reduced intensity of some As columns, suggesting the presence of antisite defects with AsB (As atom on a B site) and BAs (B atom on an As site). Additional calculations show that the antisite pair with AsB next to BAs is preferred energetically among the different types of point defects investigated and confirm that such defects lower the thermal conductivity for BAs. Using a concentration of 1.8(8)% (6.6±3.0×1020 cm-3 in density) for the antisite pairs estimated from STEM images, the thermal conductivity is estimated to be 65-100 W m-1 K-1, in reasonable agreement with our measured value. Our study suggests that AsB-BAs antisite pairs are the primary lattice defects suppressing thermal conductivity of BAs. Possible approaches are proposed for the growth of high-quality crystals or films with high thermal conductivity. Employing a combination of state-of-the-art synthesis, STEM characterization, theory, and physical insight, this work models a path toward identifying and understanding defect-limited material functionality.
| Original language | English |
|---|---|
| Article number | 105901 |
| Journal | Physical Review Letters |
| Volume | 121 |
| Issue number | 10 |
| DOIs | |
| State | Published - Sep 6 2018 |
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. The electron microscopy in this work was conducted at the ORNL\u2019s Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. C.\u2009A.\u2009P. and L.\u2009R.\u2009L. acknowledge computational resources from the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Q.\u2009Z. thanks E.-J. Guo for helpful discussions. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan .