| AVS 66th International Symposium & Exhibition | |
| 2D Materials | Wednesday Sessions |
| Session 2D+AS+MI+NS-WeM |
| Session: | 2D Materials Characterization by Scanning Probe Microscopy and Spectroscopy |
| Presenter: | Xiaolong Liu, Northwestern University |
| Authors: | X. Liu, Northwestern University L. Wang, Rice University S. Li, Northwestern University M. Rahn, Northwestern University B. Yakobson, Rice University M.C. Hersam, Northwestern University |
| Correspondent: | Click to Email |
Two-dimensional (2D) boron, known as borophene, has recently been experimentally realized1,2 revealing a number of polymorphic structures. A common characteristic of those borophene polymorphs is the presence of hollow-hexagons (HH) in an otherwise triangular lattice. The vast number of possible HH lattices underlies the polymorphic nature of borophene. Superlattices of HHs could be further realized when borophene phases periodically intermix in the form of line defects3. While scanning tunneling microscopy (STM) of borophene with conventional metal probes has revealed key features of borophene, significant ambiguity of the exact atomic lattice structure exists due to the convolution of electronic and structural details. With CO-functionalized atomic force microscopy, we unambiguously resolve the HH lattice and reveal features corresponding to B-B covalent bonds4 that are supported by numerical simulations. We further show that CO-functionalized STM is an equivalent but more accessible technique for HH imaging, allowing us to assemble a growth phase diagram of borophene involving non-rotated, 30°-rotated and randomly rotated borophene phases on Ag(111), confirming the v1/5 and v1/6 models as the unifying structures for all observed phases. In particular, a transition from rotationally commensurate to incommensurate phases is observed at high growth temperatures, corroborating the chemically discrete nature of borophene.
*Current affiliation of Xiaolong Liu: Kavli Postdoc Fellow, LASSP, Cornell University
1. A. J. Mannix, X.-F. Zhou, B. Kiraly, J. D. Wood, D. Alducin, B. D. Myers, X. Liu, B. L. Fisher, U. Santiago, J. R. Guest, M. J. Yacaman, A. Ponce, A. R. Oganov, M. C. Hersam, N. P. Guisinger, Science 350, 1513–1516 (2015).
2. B. Feng, J. Zhang, Q. Zhong, W. Li, S. Li, H. Li, P. Cheng, S. Meng, L. Chen, K. Wu, Nat. Chem. 8, 563–568 (2016).
3. X. Liu, Z. Zhang, L. Wang, B. I. Yakobson, and M. C. Hersam, Nat. Mater.17, 783–788 (2018).
4. X. Liu, L. Wang, S. Li, M. S. Rahn, B. I. Yakobson, and M. C. Hersam, Nat. Commun. 10, 1642 (2019).