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Title: Resolving the Chemically Discrete Structure of Synthetic Borophene Polymorphs

Abstract

Atomically thin two-dimensional (2D) materials exhibit superlative properties dictated by their intralayer atomic structure, which is typically derived from a limited number of thermodynamically stable bulk layered crystals (e.g., graphene from graphite). The growth of entirely synthetic 2D crystals, those with no corresponding bulk allotrope, would circumvent this dependence upon bulk thermodynamics and substantially expand the phase space available for structure-property engineering of 2D materials. However, it remains unclear if synthetic 2D materials can exist as structurally and chemically distinct layers anchored by van der Waals (vdW) forces, as opposed to strongly bound adlayers. Here, we show that atomically thin sheets of boron (i.e., borophene) grown on the Ag(111) surface exhibit a vdW-like structure without a corresponding bulk allotrope. Using X-ray standing wave-excited X-ray photoelectron spectroscopy, the positions of boron in multiple chemical states are resolved with sub-angstrom spatial resolution, revealing that the borophene forms a single planar layer that is 2.4 angstrom above the unreconstructed Ag surface. Moreover, our results reveal that multiple borophene phases exhibit these characteristics, denoting a unique form of polymorphism consistent with recent predictions. Furthermore, this observation of synthetic borophene as chemically discrete from the growth substrate suggests that it is possible to engineer amore » much wider variety of 2D materials than those accessible through bulk layered crystal structures.« less

Authors:
 [1]; ORCiD logo [2];  [1];  [3];  [4]; ORCiD logo [1]; ORCiD logo [1]
  1. Northwestern Univ., Evanston, IL (United States)
  2. Northwestern Univ., Evanston, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Diamond Light Source, Didcot (United Kingdom)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); US Department of the Navy, Office of Naval Research (ONR)
OSTI Identifier:
1482105
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 18; Journal Issue: 5; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; boron; borophene; two-dimensional materials; x-ray photoelectron spectroscopy; x-ray standing wave

Citation Formats

Campbell, Gavin P., Mannix, Andrew J., Emery, Jonathan D., Lee, Tien -Lin, Guisinger, Nathan P., Hersam, Mark C., and Bedzyk, Michael J. Resolving the Chemically Discrete Structure of Synthetic Borophene Polymorphs. United States: N. p., 2018. Web. doi:10.1021/acs.nanolett.7b05178.
Campbell, Gavin P., Mannix, Andrew J., Emery, Jonathan D., Lee, Tien -Lin, Guisinger, Nathan P., Hersam, Mark C., & Bedzyk, Michael J. Resolving the Chemically Discrete Structure of Synthetic Borophene Polymorphs. United States. doi:10.1021/acs.nanolett.7b05178.
Campbell, Gavin P., Mannix, Andrew J., Emery, Jonathan D., Lee, Tien -Lin, Guisinger, Nathan P., Hersam, Mark C., and Bedzyk, Michael J. Fri . "Resolving the Chemically Discrete Structure of Synthetic Borophene Polymorphs". United States. doi:10.1021/acs.nanolett.7b05178. https://www.osti.gov/servlets/purl/1482105.
@article{osti_1482105,
title = {Resolving the Chemically Discrete Structure of Synthetic Borophene Polymorphs},
author = {Campbell, Gavin P. and Mannix, Andrew J. and Emery, Jonathan D. and Lee, Tien -Lin and Guisinger, Nathan P. and Hersam, Mark C. and Bedzyk, Michael J.},
abstractNote = {Atomically thin two-dimensional (2D) materials exhibit superlative properties dictated by their intralayer atomic structure, which is typically derived from a limited number of thermodynamically stable bulk layered crystals (e.g., graphene from graphite). The growth of entirely synthetic 2D crystals, those with no corresponding bulk allotrope, would circumvent this dependence upon bulk thermodynamics and substantially expand the phase space available for structure-property engineering of 2D materials. However, it remains unclear if synthetic 2D materials can exist as structurally and chemically distinct layers anchored by van der Waals (vdW) forces, as opposed to strongly bound adlayers. Here, we show that atomically thin sheets of boron (i.e., borophene) grown on the Ag(111) surface exhibit a vdW-like structure without a corresponding bulk allotrope. Using X-ray standing wave-excited X-ray photoelectron spectroscopy, the positions of boron in multiple chemical states are resolved with sub-angstrom spatial resolution, revealing that the borophene forms a single planar layer that is 2.4 angstrom above the unreconstructed Ag surface. Moreover, our results reveal that multiple borophene phases exhibit these characteristics, denoting a unique form of polymorphism consistent with recent predictions. Furthermore, this observation of synthetic borophene as chemically discrete from the growth substrate suggests that it is possible to engineer a much wider variety of 2D materials than those accessible through bulk layered crystal structures.},
doi = {10.1021/acs.nanolett.7b05178},
journal = {Nano Letters},
issn = {1530-6984},
number = 5,
volume = 18,
place = {United States},
year = {2018},
month = {4}
}

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