Effect of external electric field on the surface energetics ofAg∕Si(111)

Abstract

Based on first-principles calculations, we found that the surface adsorption energetics of Ag on a Si(111) surface can be modified by imposing an external electric field. The preferred adsorption site is found to be field dependent. The most energetically favorable adsorption site of Ag on the Si(111) surface, among all the considered sites (hcp, fcc, bridge, and top), will undergo a transformation from the fcc site to the top site with an increase in field strength when the surface is positively biased. Surface diffusion and surface growth processes are influenced by various factors such as deposition rate, substrate temperature, surface reconstruction, and external stress. 1,2 It is always desirable to have additional control over such processes to attain certain metastable or stable surface configurations that are difficult or impossible to obtain with conventional procedures. The use of surfactants to achieve layer-bylayer growth 3-5 is a good example. However, surfactants may contaminate the surface and are thus of limited use in technology. Physical effects such as external fields may be advantageous since the surface remains "clean" when the external field is removed.There has been some evidence that surface morphology is strongly affected by an imposed electric field. It is well documented that potential-induced surface morphological changes are observed in metal/electrolyte interfaces. 6 An excess surface charge can induce a missing-row reconstruction on Ag(110). 7 Adatoms on the surface are stabilized by the presence of the tip and energy barriers for the diffusion processes in the region of the scanning tunneling microscopy-(STM) tip. 8 The presence of an electrostatic field is found to dramatically enhance the kinetics of Al(111) oxidation when O 2 molecules interact with the charged surface after electron bombardment. 9 It was also found that the electric field or surface charging can stabilize surface vacancy arrays in metal bcc(100) surfaces, leading to a change of surface configurations. 10 The field effects on Si ad-dimer diffusion on Si(001) have been shown by experimental 11 and theoretical 12 investigations. The electric field effect on surface diffusion has been investigated by the field ion microscopy (FIM) technique. Kellogg has found that an external electric field can indeed inhibit or promote surface selfdiffusion on Pt(001) surface, 13 and Feibelman tried to explain this experimental observation using ab initio calculations. 14 In this work, we will demonstrate that an externally imposed electric field may indeed modify or control surface adsorption energetics. Because of its importance for a wide variety of surface phenomena (STM, FIM, electrochemical interfaces), understanding the influence of an electric field on surface properties is also essential for interpreting some experimental results.Our main finding is that the binding energy of Ag on various sites of the Si(111) substrate could be influenced by an external electric field applied to the surfaces. For the case of zero electr...

Effects of an electric field on a water bilayer on Ag(111)

“…The discrepancy may be attributed to the E-field effect on the OH bond, which is perpendicularly pointing toward the vacuum and exposed directly under the E field due to the field induced charge transfer; see our previous work for details. 25 …”

Local changes of work function near rough features on Cu surfaces operated under high external electric field

“…2,13 In this study we used the density functional theory (DFT) approach, which was successfully employed previously by other authors to calculate the work function modification due to molecules of surface contaminants. [14][15][16][17][18][19][20][21] However, in some demanding applications it is of great importance to know how the work function is modified due to intrinsic surface defects like self-adatoms and step edges, which will contribute in the re-arrangement of the surface topology under the electric field as well as contribute in explanation of a sudden rise of field emission currents on seemingly flat metal surfaces. Moreover, in ultra high vacuum (UHV) and in the presence of high electric fields, the contaminant layer becomes insignificant after a short operation time.…”

Electric-field effects on the diffusion of Si and Ge adatoms on Si(001) studied by density functional simulations

“…According to recent first-principles calculations implementing under an external electric field, there has been strong evidence that diffusion of adsorbates can be significantly influenced by an external electric field. 5,7,8 The stable adsorption site of Ag on Si͑111͒ will be changed from fcc site to top site as applied electric field reaches a value of 1.2 V / Å. The surface diffusion rate of Ag on Si͑111͒ will enhance gradually with increasing field strength, and rapidly reach a maximum value as field being 1.2 V / Å.…”

“…The surface diffusion rate of Ag on Si͑111͒ will enhance gradually with increasing field strength, and rapidly reach a maximum value as field being 1.2 V / Å. 7 We further investigate the electric-field effects on the dynamic behavior of Si ͑Ge͒ adatoms on Si͑001͒ surface, since control of fundamental atomistic processes that govern the surface kinetics of epitaxial growth of Si-Ge materials is of considerable scientific interest and technological importance. Although Si͑111͒ is the most popular semiconductor surface in academic research, Si͑001͒ is a dominant substrate for electronic devices in silicon industry.…”

“…Our ab initio calculations will present valuable information about dynamic behavior of Si ͑Ge͒ on Si͑001͒ and will further confirm our conclusions about surface diffusion under an external electric field, which were obtained from our calculations based on an assumption of the surface with a simple ͑1 ϫ 1͒ structure. 7 Thus, this technique allows us to control surface dynamic process by turning on and off an external electric field.…”