X-ray Photoelectron Difraction of MgO(111)-(1x1)
EMSL Project ID
11290
Abstract
The objective of this study is to collect preliminary data to experimentally distinguish between two recently proposed mechanisms for the stabilization of the polar MgO(111)-(1x1) surface termination: 1) hydroxyl adsorption; 2) metalization with surface relaxation.The fundamental scienctific and technological importance of the MgO(111)-(1x1) surface is that it essentially consists of layers of magnesium only or oxygen only atoms. But either configuration alone has been predicted by P.W. Tasker (J. Phys. C, 12 (1979) 4997.) to lead to an infinite surface energy. However, we have routinely observed 1x1 surface spots boy TED and LEED on MgO(111) and NiO(111) samples which have been either acid etched or Ar+ ion milled and then annealed (in air or in vacuum) to between 500-1000 degrees Celsius. Unfortuneley the TED structure techniques tht we have used for the 2x2, (rt3xrt3)R30 and (2rt3x2rt3)R30 reconstructions of MgO(111) (Plass et al. PRL 81, 4891 (1998)) can not be applied to 1x1 type structrues.
The 1x1 surface, however, is the most controversial from the theoretical viewpoint. The theoretical modeling of Pojani et al. (surf. Sci., 387 (1997) 354.) suggest that hydrogen bonded to an outermost oxygen layer could stbilize this system. Contrary to this model, Noguera has recently predicted states in the bandgap for the bukl terminated MgO(111) surface, and has called this effect a metalization mechanism for the reduction of the infinite surface energy of the 1x1 polar surface. She predicted a relaxation of the topmost layer 9in both the O thermination and Mg termination secnarios).
The logistics of the experiment involve polishing a 1cm x 1cm x 0.4mm MgO(111) single crystal slab at University of Wisconsin Milwaukee and annealing it in an air furnace to 500 or more degrees Celsius along with a comparably prpared TEM sample
Once the 1x1 reconstruction has been verified on the TEM sample thl larger slab will be sent to PNNL. There initial XPS an XPD data will be taken and if needed the sample can be ion milled clean and reannealed resistively under vacuum as needed and the diffraction data retaken. Data analysis will occur jointly with Dr. Scott Chambers and very likely with the help of Santanu Banerfee, as student of Professor Brian Tonner, and the University of Wisconsin, Milwaukee.
Project Details
Project type
Exploratory Research
Start Date
2004-09-13
End Date
2005-10-06
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Lazarov V, M Weinert, SA Chambers, and M Gajdardziska-josifovska. 2005. "Atomic and Electronic Structure of the Fe?O? (111)/MgO(111) Model Polar Oxide Interface." Physical Review. B, Condensed Matter 72(19):195401.
Lazarov V, SA Chambers, and M Gajdardziska-Josifovska. 2003. "Polar Oxide Interface Stabilization by Formation of Metallic Nanocrystals." Physical Review Letters 90(21):216108.
Structure of the hydrogen-stabilized MgO(111)-(1X1) polar surface: Integrated experimental and theoretical studies