The structure and electronic properties of tetrahedrally bonded hydrogenated amorphous carbon

A. G. Salek; P. Y. Le; J. G. Partridge; T. J. Raeber; B. Haberl; R. Boehler; B. J. Murdoch; J. E. Bradby; T. Ratcliff; R. G. Elliman; D. R. McKenzie; D. G. McCulloch

doi:10.1063/5.0147494

The structure and electronic properties of tetrahedrally bonded hydrogenated amorphous carbon

A. G. Salek, P. Y. Le, J. G. Partridge, T. J. Raeber, B. Haberl, R. Boehler, B. J. Murdoch, J. E. Bradby, T. Ratcliff, R. G. Elliman, D. R. McKenzie, D. G. McCulloch

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Abstract

We have synthesized hydrogenated and deuterated amorphous carbon materials that have a density, 2.7 ± 0.1 g/cm³, consistent with almost entirely tetrahedral bonding. In hydrogen-free tetrahedral amorphous carbon, the presence of a minority of sp² bonded atoms leads to localized states that could be passivated with hydrogen by analogy with hydrogenated amorphous silicon. Neutron diffraction analysis demonstrated that the local bonding environment is consistent with ab initio models of high density hydrogenated tetrahedral amorphous carbon and with the related tetrahedral molecular structure neopentane. The optical bandgap of our material, 4.5 eV, is close to the bandgap in the density of states determined by scanning tunneling spectroscopy (4.3 eV). This bandgap is considerably larger than that of hydrogen-free tetrahedral amorphous carbon, confirming that passivation of sp² associated tail-states has occurred. Both the structural and electronic measurements are consistent with a model in which the tetrahedrally bonded carbon regions are terminated by hydrogen, causing hopping conductivity to dominate.

Original language	English
Article number	181904
Journal	Applied Physics Letters
Volume	122
Issue number	18
DOIs	https://doi.org/10.1063/5.0147494
State	Published - May 1 2023

Funding

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 ( http://energy.gov/downloads/doe-public-access-plan ).

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U.S. Department of Energy

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title = "The structure and electronic properties of tetrahedrally bonded hydrogenated amorphous carbon",

abstract = "We have synthesized hydrogenated and deuterated amorphous carbon materials that have a density, 2.7 ± 0.1 g/cm3, consistent with almost entirely tetrahedral bonding. In hydrogen-free tetrahedral amorphous carbon, the presence of a minority of sp2 bonded atoms leads to localized states that could be passivated with hydrogen by analogy with hydrogenated amorphous silicon. Neutron diffraction analysis demonstrated that the local bonding environment is consistent with ab initio models of high density hydrogenated tetrahedral amorphous carbon and with the related tetrahedral molecular structure neopentane. The optical bandgap of our material, 4.5 eV, is close to the bandgap in the density of states determined by scanning tunneling spectroscopy (4.3 eV). This bandgap is considerably larger than that of hydrogen-free tetrahedral amorphous carbon, confirming that passivation of sp2 associated tail-states has occurred. Both the structural and electronic measurements are consistent with a model in which the tetrahedrally bonded carbon regions are terminated by hydrogen, causing hopping conductivity to dominate.",

author = "Salek, {A. G.} and Le, {P. Y.} and Partridge, {J. G.} and Raeber, {T. J.} and B. Haberl and R. Boehler and Murdoch, {B. J.} and Bradby, {J. E.} and T. Ratcliff and Elliman, {R. G.} and McKenzie, {D. R.} and McCulloch, {D. G.}",

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AU - Salek, A. G.

AU - Le, P. Y.

AU - Partridge, J. G.

AU - Raeber, T. J.

AU - Haberl, B.

AU - Boehler, R.

AU - Murdoch, B. J.

AU - Bradby, J. E.

AU - Ratcliff, T.

AU - Elliman, R. G.

AU - McKenzie, D. R.

AU - McCulloch, D. G.

PY - 2023/5/1

Y1 - 2023/5/1

N2 - We have synthesized hydrogenated and deuterated amorphous carbon materials that have a density, 2.7 ± 0.1 g/cm3, consistent with almost entirely tetrahedral bonding. In hydrogen-free tetrahedral amorphous carbon, the presence of a minority of sp2 bonded atoms leads to localized states that could be passivated with hydrogen by analogy with hydrogenated amorphous silicon. Neutron diffraction analysis demonstrated that the local bonding environment is consistent with ab initio models of high density hydrogenated tetrahedral amorphous carbon and with the related tetrahedral molecular structure neopentane. The optical bandgap of our material, 4.5 eV, is close to the bandgap in the density of states determined by scanning tunneling spectroscopy (4.3 eV). This bandgap is considerably larger than that of hydrogen-free tetrahedral amorphous carbon, confirming that passivation of sp2 associated tail-states has occurred. Both the structural and electronic measurements are consistent with a model in which the tetrahedrally bonded carbon regions are terminated by hydrogen, causing hopping conductivity to dominate.

AB - We have synthesized hydrogenated and deuterated amorphous carbon materials that have a density, 2.7 ± 0.1 g/cm3, consistent with almost entirely tetrahedral bonding. In hydrogen-free tetrahedral amorphous carbon, the presence of a minority of sp2 bonded atoms leads to localized states that could be passivated with hydrogen by analogy with hydrogenated amorphous silicon. Neutron diffraction analysis demonstrated that the local bonding environment is consistent with ab initio models of high density hydrogenated tetrahedral amorphous carbon and with the related tetrahedral molecular structure neopentane. The optical bandgap of our material, 4.5 eV, is close to the bandgap in the density of states determined by scanning tunneling spectroscopy (4.3 eV). This bandgap is considerably larger than that of hydrogen-free tetrahedral amorphous carbon, confirming that passivation of sp2 associated tail-states has occurred. Both the structural and electronic measurements are consistent with a model in which the tetrahedrally bonded carbon regions are terminated by hydrogen, causing hopping conductivity to dominate.

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The structure and electronic properties of tetrahedrally bonded hydrogenated amorphous carbon

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