Combined ab initio and XPS Investigations of the Electronic Interactions of L-Cysteine Adsorbed on GaAs(1 0 0)

MARÍA F. JUAREZ; ELIZABETH SANTOS; CATALIN NEGRILA; ANA M. TOADER; VALENTINA LAZARESCU

Chemistry select

WIley

Año: 2016 vol. 1 p. 3623 - 3634

The adsorption of L-cysteine from ethanol solutions on GaAs(1 0 0) surfaces has beenstudied by XPS and density-functional theory (DFT). XPS data reveal that theformation of the adsorbate involves preferentially the As-sites for p-GaAs(1 0 0) andthe Ga-sites for n-GaAs(1 0 0). The adsorbed species show different orientations of thefunctional groups to the surface for the different substrates. DFT calculationsperformed for both Ga-dimers and As-dimers terminated surfaces show that theadsorption is energetically favourable on both substrates. However, the adsorptionenergy is more negative on top of Ga-atoms. Here an important contribution for thestabilization of the adsorbate is the interaction of the functional groups with the surface.The parallel orientation found for the Ga-bound species by DFT calculations is in goodagreement with the shift in the binding energy of the NH2/NH3+ species observed byXPS analysis.