AVS 61st International Symposium & Exhibition
    Surface Science Tuesday Sessions
       Session SS+AS+EN-TuM

Paper SS+AS+EN-TuM6
Design Rules for Stabilizing Polar Metal Oxide Surfaces: Adsorption of O2 on Zn-rich Polar ZnO(0001)

Tuesday, November 11, 2014, 9:40 am, Room 309

Session: Synthesis, Structure and Characterization of Oxides
Presenter: Ming Li, University of Illinois at Urbana-Champaign
Authors: M. Li, University of Illinois at Urbana-Champaign
P. Gorai, University of Illinois at Urbana-Champaign
E. Ertekin, University of Illinois at Urbana-Champaign
E.G. Seebauer, University of Illinois at Urbana-Champaign
Correspondent: Click to Email
For oxide semiconductors with appreciable ionic character, under-coordination of the surface atoms leads to thermodynamic instability that is typically restored by reconstruction, faceting, or extensive surface defect creation. Developing design rules for stabilizing polar metal oxide surfaces that avoid these phenomena could offer novel protocols for applications such as improved nanostructure growth and design of photocatalytic heterostructures. The present work describes calculations by density functional theory for Zn-rich polar ZnO(0001) which demonstrate that stabilization via chemisorbed O2 together with vacancy formation is energetically as favorable as stabilization by vacancies alone. The stabilization mechanism including adsorption is so effective that it promotes O2 adsorption to an extent that is not possible on non-polar ZnO. Experimental evidence for such stabilization behavior is presented based on measurements of O2 adsorption on polar ZnO(0001) via the optical modulation technique of photoreflectance. The measured isotherms yield a sizable adsorption enthalpy of adsorption near 1.8eV, confirming a strong interaction with the polar surface.