Chemical Elements on Substrates

Fomenko, V. S.; Samsonov, G. V.

doi:10.1007/978-1-4684-7293-6_4

Cited by 13 publications

(13 citation statements)

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“…Note the strong linear proportionality, confirming simple expectations from the photoelectric effect that the maximum kinetic energies increase with total photon energy, with the intercept yielding the work function, ϕ film = 4.46(5) eV. This value is lower than observed for atomically clean, single-crystal gold surfaces (5.1 eV) but consistent with measurements of polycrystalline gold surfaces exposed to ambient air/water vapor . This decrease in work function with ambient exposure has been interpreted as arising from a molecular adlayer, which can suppress the inherent dipole layer at the metal surface and decrease the corresponding potential barrier .…”

Section: Resultssupporting

confidence: 80%

Angle- and Momentum-Resolved Photoelectron Velocity Map Imaging Studies of Thin Au Film and Single Supported Au Nanoshells

2018

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Transverse (2D) photoelectron velocity distributions are directly measured on 10 nm Au film and single Au nanoshells following multiphoton excitation/photoemission. This unique capability is achieved by combining scanning photoemission microscopy with velocity map imaging, yielding photoelectron spectra as a function of diffraction-limited position on a sample. Detailed 3D photoelectron velocity distributions are retrieved for Au film by fitting the 2D data with a ballistic (three-step) photoemission model, where contributions from two-photon, threephoton, and d-band processes are identified and further characterized as a function of photon energy using a broadly tunable, visible femtosecond optical parametric oscillator. These techniques are further applied to investigate the more complex behaviors of single plasmonic Au nanoshells with silica cores. The strong plasmonic near-and far-field signatures are first characterized via optical and photoemission measurements, along with theoretical methods (Mie theory and finite element analysis). This is followed by measurements of the transverse photoelectron velocity distributions for single nanoshells, which reveal at least one surprising result. Specifically, nearly perfect azimuthal symmetry is evident in the nanoshell electron momentum distributions, despite linearly polarized excitation and anisotropic near-electric-field distributions corresponding to the dipolar/quadrupolar plasmon modes. It is demonstrated that this isotropy is at least partially due to photoelectrons scattering with physisorbed or chemisorbed surface molecules during the photoemission process.

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Section: Resultssupporting

confidence: 80%

Angle- and Momentum-Resolved Photoelectron Velocity Map Imaging Studies of Thin Au Film and Single Supported Au Nanoshells

2018

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“…In the case where d ALD = 0, the contact radius is more accurately described by a b contact, , where b is the decay length of an electron in the medium surrounding the nanocrystals, which depends on the work function, and r 0 is the particle radius . Using a work function of 4.7 eV for Al 2 O 3 , b is approximately 0.1 nm, and therefore r C ( d ALD = 0) ≈ 0.6 nm. Thus, the contact radius can be calculated as a function of experimental conditions and the measured particle radius, r 0 .…”

Section: Resultsmentioning

confidence: 99%

Contact Radius and the Insulator–Metal Transition in Films Comprised of Touching Semiconductor Nanocrystals

Lanigan

Thimsen

2016

ACS Nano

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Nanocrystal assemblies are being explored for a number of optoelectronic applications such as transparent conductors, photovoltaic solar cells, and electrochromic windows. Majority carrier transport is important for these applications, yet it remains relatively poorly understood in films comprised of touching nanocrystals. Specifically, the underlying structural parameters expected to determine the transport mechanism have not been fully elucidated. In this report, we demonstrate experimentally that the contact radius, between touching heavily doped ZnO nanocrystals, controls the electron transport mechanism. Spherical nanocrystals are considered, which are connected by a circular area. The radius of this circular area is the contact radius. For nanocrystals that have local majority carrier concentration above the Mott transition, there is a critical contact radius. If the contact radius between nanocrystals is less than the critical value, then the transport mechanism is variable range hopping. If the contact radius is greater than the critical value, the films display behavior consistent with metallic electron transport.

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“…The second one is molecular ion dissociation. There is evidence that under the effect of a strong electric field, metastable molecules or clusters may decompose into two or more small fragments which will also lead to multiple events (Tsong, 1985; Saxey, 2011; La Fontaine et al, 2015; Santhanagopalan et al, 2015; Gault et al, 2016). Intrinsically, fraction of the multiple events is field-dependent.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Analysis Conditions for Laser-Pulsed Atom Probe Tomography: Example of Cemented Tungsten Carbide

et al. 2017

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Cemented tungsten carbide has been analyzed using laser-pulsed atom probe tomography (APT). The influence of experimental parameters, including laser pulse energy, pulse repetition rate, and specimen base temperature, on the acquired data were evaluated from different aspects, such as mass spectrum, chemical composition, noise-to-signal ratio, and multiple events. Within all the applied analysis conditions, only 1 MHz pulse repetition rate led to a strong detector saturation effect, resulting in a largely biased chemical composition. A comparative study of the laser energy settings showed that an ~12 times higher energy was required for the less focused green laser of the LEAPTM 3000X HR system to achieve a similar evaporation field as the finer spot ultraviolet laser of the LEAPTM 5000 XS system.

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Chemical Elements on Substrates

Cited by 13 publications

References 0 publications

Angle- and Momentum-Resolved Photoelectron Velocity Map Imaging Studies of Thin Au Film and Single Supported Au Nanoshells

Angle- and Momentum-Resolved Photoelectron Velocity Map Imaging Studies of Thin Au Film and Single Supported Au Nanoshells

Contact Radius and the Insulator–Metal Transition in Films Comprised of Touching Semiconductor Nanocrystals

Evaluation of Analysis Conditions for Laser-Pulsed Atom Probe Tomography: Example of Cemented Tungsten Carbide

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