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Register a new userMechanisms for carbon adsorption on Au(110)-(2*1): A work function analysis
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The variation of the work function upon carbon adsorption on the reconstructed Au(110) surface is measured experimentally and compared to density functional calculations. The adsorption dynamics is simulated with ab-initio molecular dynamics techniques. The contribution of various energetically available adsorption sites on the deposition process is analyzed, and the work function behavior with carbon coverage is explained by the resultant electron charge density distributions.
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We investigate the work function (WF) variation of different Au crystallographic surface orientations with carbon atom adsorption. Ab-initio calculations within density-functional theory are performed on carbon deposited (100), (110), and (111) gold surfaces. The WF behavior with carbon coverage for the different surface orientations is explained by the resultant electron charge density distributions. The dynamics of carbon adsorption at sub-to-one-monolayer (ML) coverage depends on the landscape of the potential energy surfaces. At higher ML coverage, because of adsorption saturation, the WF will have weak surface orientation dependence. This systematic study has consequential bearing on studies of electric-field noise emanating from polycrystalline gold ion-trap electrodes that have been largely employed in microfabricated electrodes.
The decoherence of trapped-ion quantum gates due to heating of their motional modes is a fundamental science and engineering problem. This heating is attributed to electric-field noise arising from the trap-electrode surfaces. In this work, we investigate the source of this noise by focusing on the diffusion of carbon-containing adsorbates on the surface of Au(110). We show by density functional theory, based on detailed scanning probe microscopy, how the carbon adatom diffusion on the gold surface changes the energy landscape, and how the adatom dipole moment varies with the diffusive motion. A simple model for the diffusion noise, which varies quadratically with the variation of the dipole moment, qualitatively reproduces the measured noise spectrum, and the estimate of the noise spectral density is in accord with measured values.
Detecting dopamine is of great biological importance because the molecule plays many roles in the human body. For instance, the lack of dopamine release is the cause of Parkinsons disease. Although many researchers have carried out experiments on dopamine detection using carbon nanotubes (CNTs), there are only a few theoretical studies on this topic. We study the adsorption properties of dopamine and its derivatives, L-DOPA and dopamine o-quinone, adsorbed on a semiconducting (10, 0) CNT, using density functional theory calculations. Our computational simulations reveal that localized states originating from dopamine o-quinone appear in the bandgap of the (10, 0) CNT, but those originating from dopamine and L-DOPA do not appear in the gap. Therefore, dopamine o-quinone is expected to be detectable using an external electric field but dopamine and L-DOPA should be difficult to detect.
Au-Cu bimetallic nanoparticles (NPs) grown on TiO 2 (110) have been followed in-situ using grazing incidence x-ray diffraction and x-ray photoemission spectroscopy from their synthesis to their exposure to a CO/O 2 mixture at low pressure (P < 10-5 mbar) and at different temperatures (300 K-470 K). As-prepared samples are composed of two types of alloyed NPs: randomly oriented and
We demonstrate and interpret a technique of laser-induced formation of thin metallic films using alkali atoms on the window of a dense-vapour cell. We show that this intriguing photo-stimulated process originates from the adsorption of Cs atoms via the neutralisation of Cs$^+$ ions by substrate electrons. The Cs$^+$ ions are produced via two-photon absorption by excited Cs atoms very close to the surface, which enables the transfer of the laser spatial intensity profile to the film thickness. An initial decrease of the surface work function is required to guarantee Cs$^+$ neutralisation and results in a threshold in the vapour density. This understanding of the film growth mechanism may facilitate the development of new techniques of laser-controlled lithography, starting from thermal vapours.
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