Formation and Dynamics of Electron-Irradiation-Induced Defects in Hexagonal Boron Nitride at Elevated Temperatures.
The atomic structure, stability, and dynamics of defects in hexagonal boron nitride (h-BN) are investigated using an aberration-corrected transmission electron microscope operated at 80 kV between room temperature and 1000 °C. At temperatures above 700 °C, parallelogram- and hexagon-shaped defects with zigzag edges become prominent, in contrast to the triangular defects typically observed at lower temperatures. The appearance of 120° corners at defect vertices indicates the coexistence of both N- and B-terminated zigzag edges in the same defect. In situ dynamics studies show that the hexagonal holes grow by electron-induced sputtering of B-N chains, and that at high temperatures these chains can migrate from one defect corner to another. We complement the experiments with first-principles calculation which consider the thermal equilibrium formation energy of different defect configurations. It is shown that, below a critical defect size, hexagonal defects have the lowest formation energy and therefore are the more-stable configuration, and triangular defects are energetically metastable but can be "frozen in" under experimental conditions. We also discuss the possible contributions of several dynamic processes to the temperature-dependent defect formation.
Department of Physics, University of California , Berkeley, California 94720, United States.|Department of Materials Science and Engineering, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.|Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.
Thang
T
Pham
Department of Physics, University of California , Berkeley, California 94720, United States.|Department of Chemistry, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.|Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.
Ashley L
AL
Gibb
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.
Zhenglu
Z
Li
Department of Physics, University of California , Berkeley, California 94720, United States.|Department of Chemistry, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.|Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.
S Matt
SM
Gilbert
The Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.
Chengyu
C
Song
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.
Steven G
SG
Louie
Department of Physics, University of California , Berkeley, California 94720, United States.|Department of Chemistry, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.|Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory , Berkeley, California 94720 United States.
Alex
A
Zettl
Hexagonal boron−nitride; aberration-corrected transmission electron microscopy; boron-terminated edge; first-principles calculations; hexagon defect; in situ heating