First-Principle Study Of Ag Deposition On MgO(001) Surface

Metal/oxide interfaces play an important role in various technological applications such as catalysis,composite material,microelectronics and photovoltaic device,magnetic nanostructures.Acted as a typical metal/oxide system,it has motivated an increasing interest towards the fundamental structural,physical and chemical properties of this system over the last years.In this work,The Ag/MgO(001) system has been studied by first-principle method based on density-function theory,adsorption of Ag_n(n = 1～5) clusters on MgO(001) surface have been investigated to elucidate the initial stage of Ag atom deposition on MgO surface.It was found that the preferential adsorption site for an isolated Ag atom is directly above the surface oxygen atom and a weak bond is formed.Various structural configurations have been examined for the Ag_n clusters and standing planar structures were found to be energetically more stable than flat planar structures.Energy and electronic properties revealed that with the increase of Ag coverage,the interaction of adsorbate-adsorbate bonds prevails over adsorbate-substrate bonds,this make the Ag atom prefer to diffuse across the relatively low energy barrier on MgO(001) surface and bond with the previous Ag atom,leads to a volmer-weber mode deposition.In real conditions,the substrate surface always have some kind of defects,such as vacancy,step,depends on the preparing technology,these defects take a great affection on the property of metal atoms deposition on MgO surface,espically for the vacancy,it played a key role for the nucleation and growth of metal nanoclusters on oxide surfaces.Using first-principle method,we have studied the interaction of Ag clusters defective MgO(001) surface with neutral and charged oxygen vacancies,Fs and Fs~+,the results showed that for the single Ag atom,the bond between Ag atom and Fs~+ is more stong than that of Ag atom and Fs site.But for the Ag cluster adsorption,the adsorption energy and adhesion at Fs site is bigger than Fs~+ site,the reason is,on an Fs~+ center the formation of a strong covalent bond between the surface and the Ag atom results in a low tendency of the surface complex to add additional Ag atoms.