Stabilization of Zinc-Terminated ZnO(0001) by a Modified Surface Stoichiometry

Abstract

The stabilization of polar oxide surfaces is of fundamental interest for understanding many processes in surface chemistry. We study the zinc-terminated Zn-ZnO(0001), a surface important in heterogeneous catalysis, by highest resolution scanning force microscopy (SFM) operated in the noncontact mode (NC-AFM). While most of the surface morphology is dominated by a phase consisting of triangular shaped nanostructures, we observe a coexisting (1 × 3) reconstructed phase where the reconstruction is ascribed to the formation of missing Zn-rows. Our findings provide evidence that the electrostatic instability of the polar Zn-ZnO(0001) surface can be canceled by a reduction of the surface charge by 1/3 which is considerably larger than the value of 1/4 derived from a simple ionic model for polar stabilization. Within the presented model for the (1 × 3) reconstruction, the role of point defects tentatively ascribed to hydrogen adsorbed on top of double Zn-rows forming zinc-hydride is discussed.

Room-temperaturep-induced surface ferromagnetism: First-principles study

“…The magnetic interaction between spin moments is strong and the calculated Curie temperature is 300 K.The surface is thermodynamically stable in a significant range of oxygen pressures. The presence of oxygen atoms in extended local areas of the (0001) surface has been experimentally reported either in rough surfaces with incomplete O terminations 16 or in ordered structures 17 and has been suggested to be a stabilization mechanism of the (0001) surface with Zn polarity. 18 The present paper is structured as follows.…”

Spin-polarized Wide Electron Slabs in Functionally Graded Polar Oxide Heterostructures

“…In fact, during the step-flow growth under thermal equilibrium, the different growth speed is determined by different dangling bond densities at two kinds of step edges, leading to the jagged structures. The theoretical calculations and experimental results suggests that these step edges are O-terminated and thereby result in the overall decrease of the surface Zn concentration, which in turn build in a net-electric field to compensate the electrostatic surface instability2122. On the other hand, the lattice-mismatch induced compressive strain in ZnMgO will tend to relax and give priority to the formation of tiny pits at the step edges of terraces.…”

Hydrogen released from bulk ZnO single crystals investigated by time-of-flight electron-stimulated desorption

“…16,17 It is known that these two polar surfaces have different physical and chemical properties. [18][19][20][21][22][23][24] By using cathodoluminescence ͑CL͒, it has been found that the ultraviolet ͑UV͒ intensity decreases exponentially as a function of irradiation time for the O-face, while it first increases and then decreases for the Zn-face. 13,15 Notably, the decrease in the UV intensity is comparable for both faces.…”