title: Ultralow effective work function surfaces using diamondoid monolayers.
abstract: Electron emission is critical for a host of modern fabrication and analysis applications including mass spectrometry, electron imaging and nanopatterning. Here, we report that monolayers of diamondoids effectively confer dramatically enhanced field emission properties to metal surfaces. We attribute the improved emission to a significant reduction of the work function rather than a geometric enhancement. This effect depends on the particular diamondoid isomer, with [121]tetramantane-2-thiol reducing gold's work function from ∼ 5.1 eV to 1.60 ± 0.3 eV, corresponding to an increase in current by a factor of over 13,000. This reduction in work function is the largest reported for any organic species and also the largest for any air-stable compound. This effect was not observed for sp(3)-hybridized alkanes, nor for smaller diamondoid molecules. The magnitude of the enhancement, molecule specificity and elimination of gold metal rearrangement precludes geometric factors as the dominant contribution. Instead, we attribute this effect to the stable radical cation of diamondoids. Our computed enhancement due to a positively charged radical cation was in agreement with the measured work functions to within ± 0.3 eV, suggesting a new paradigm for low-work-function coatings based on the design of nanoparticles with stable radical cations.
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.|Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Karthik Thimmavajjula
authors.initials: KT
authors.lastname: Narasimha
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.|Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Chenhao
authors.initials: C
authors.lastname: Ge
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.|Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Fabbri
authors.affiliation: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: William
authors.initials: W
authors.lastname: Clay
authors.affiliation: Institute of Organic Chemistry, Justus-Liebig University, Giessen, Heinrich-Buff-Ring 17, Giessen 35392, Germany.
authors.forename: Boryslav A
authors.initials: BA
authors.lastname: Tkachenko
authors.affiliation: Institute of Organic Chemistry, Justus-Liebig University, Giessen, Heinrich-Buff-Ring 17, Giessen 35392, Germany.|Kiev Polytechnic Institute, pr. Pobedy 37, Kiev 03056, Ukraine.
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Fokin
authors.affiliation: Institute of Organic Chemistry, Justus-Liebig University, Giessen, Heinrich-Buff-Ring 17, Giessen 35392, Germany.
authors.forename: Peter R
authors.identifier: http://orcid.org/0000-0002-3608-5515
authors.initials: PR
authors.lastname: Schreiner
authors.affiliation: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Jeremy E
authors.initials: JE
authors.lastname: Dahl
authors.affiliation: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Robert M K
authors.initials: RM
authors.lastname: Carlson
authors.affiliation: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Z X
authors.initials: ZX
authors.lastname: Shen
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.|Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Melosh