Model oxide defects with vicinally stepped NiO(100) substrates
EMSL Project ID
19391
Abstract
We propose atomic force microscopy (AFM) studies of vicinally-stepped NiO(001) substrates designed to present periodic surface atomic edge sites and narrow terraces of constant atomic width. The vicinally-stepped substrates serve as models for under-coordinated defects at transition metal oxide surfaces, prime sites for adsorption and catalytic activity, and can be used to manipulate adsorbate geometry, for example in forcing aromatic adsorbates that typically bond in ring-parallel form into a tilted geometry relative to the terrace plane. The vicinal step structure can be varied to have different step edge density and step-edge morphology in a controllable and well-characterized manner. This proposal is for general user time and is in response to the Science Theme Call in the area of Science of Interfacial Phenomena.Our group has perfected a protocol for creating vicinal steps on NiO(001) substrate, has characterized them with low energy electron diffraction and x-ray photoelectron spectroscopy, and has studied their adsorption properties by thermal desorption mass spectrometry of halocarbon adsorbates. Thus, the vicinally-stepped NiO(001) substrates are presently available and in situ sample preparation protocols have already been developed. The Interfacial & Nanoscale Science Facility within the WR Wiley Environmental Molecular Sciences Laboratory is particularly suitable for undertaking the proposed AFM studies. Dr. Igor Lyubinetsky, staff scientist at EMSL, specializes in the use of non-contact AFM for studying surface chemistry of metal oxide materials at the atomic level and is interested in collaborating with us to study the vicinally stepped NiO(001) substrates.
The first studies to be performed will be to image the periodic step structure. Unstepped NiO(001), cut and polished by indentical methods to the stepped substrates, will also be included for comparison to surface quality and defect structure. Details of the step edges will then be probed. The studies proposed here are estimated to require approximately a month of AFM equipment time, which can be undertaken either in a single block of time or in smaller periods of five to seven days for each substrate, as is convenient for scheduling purposes. There are four NiO(001) substates, three vicinally-stepped with 5, 6 and 7 atom-terraces and one unstepped, to be analyzed by AFM, XPS and LEED after in situ treatment to produce clean, stoichiometric and hydroxyl-free substrates. Experimentation is to be performed by the P.I., who will be on sabbatical at PNNL during the requested time. Contacts at PNNL are Mike Henderson (the P.I.?s host for sabbatical) and Igor Lubyinetsky (general user proposal host). Further experiments can be envisioned, including imaging/surface analysis of adsorbate/stepped substrate complexes and AFM of step geometries produced from other parent orientations and/or other step directions. These latter experiments will be addressed in future collaborative efforts.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2006-09-01
End Date
2009-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members