Doctoral College TU-D Unravelling advanced 2D materials
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Unravelling the Complexity of Ternary Metal Oxide Surfaces

Gareth Parkinson, Institute of Applied Physics

Gareth Parkinson focuses on the study of complex metal oxide surfaces, and understanding how the atomic-scale structure links to the electronic and magnetic properties, and chemical reactivity. To achieve this goal, scanning probe microscopies, quantitative structural determinations, and high-resolution spectroscopies are combined with theoretical calculations. For example, the structure of the Fe3O4(001) surface was recently solved [1], which explains the earlier discovery that ordered arrays of metal adatoms can be stabilized on this surface [2]. This unique adsorption template has already been used to study the nucleation and growth of Ag clusters [3], CO induced mobility of Pd adatoms [4], and CO oxidation over supported Pt clusters [5]. In future, he aims to use his recent FWF START award to understand how single metal atom catalyze chemical reactions, and to perform pioneering studies of complex ternary metal oxide surfaces. 

PhD Project 1: Ultrathin Films of Spinel Ferrites

Co-supervisor: Peter Blaha    

Spinel compounds (general formula AB2X4) have emerged as an exciting vehicle to engineer functional materials because the properties vary dramatically with the nature of the A and B cations. Little is known about their surface properties however, and of the 150 stable metal-oxide compounds (i.e. X = O2-), only Fe3O4 has received significant attention from the surface science community. In this project we will prepare 2D films of the ferrite (XFe2O4) family by incorporating foreign metal atoms into cation vacancies present in the Fe3O4(001) surface. This approach will allow us to study insulating materials by STM and electron spectroscopies (Fe3O4 provides a metallic support), and allows us to systematically vary the metal cation. Our extensive knowledge of Fe3O4(001) surface will serve as a benchmark to compare the structural, electronic and magnetic properties of the novel 2D ferrite systems, which have additional applications as tunnel barriers in spintronics. This project will continue the highly successful collaboration with Peter Blaha.

PhD Project 2: Surface Chemistry of Perovskite Oxides

Co-supervisor: Florian Libisch


Perovskites represent some of the most excting materials in solid state physics with applications including memristors, solid oxide fuel cells, and heterogeneous catalysis. Chemistry occurring at the perovskite surface/interface are vital to performance, but almost nothing is known about perovskite surface chemistry. In this project we will grow thin films of important perovskite materials (LSMO, LCO, LFO) on STO using pulsed layer deposition and study their surface structure in-situ using STM/AFM, LEED, and XPS. The formation of the intial monolayer be studied, which can shed light on the interface structure in heterostructured devices. Adsorption experiments will focus on molecules relevant to applications such as O2 and H2O. The reactivity of the surfaces with be studied using a new state of the art surface chemistry set up recently commissioned at the TU Wien. Throughout, DFT calculations performed via a new collaboration with Florian Libisch, and this will be vital to help us interpret the experimental data, and to model the interation of adsorbates with the surface.


Literature

  1. R. Bliem, et al. Subsurface cation vacancy stabilization of the magnetite (001) surface, Science 346, 1215-1218 (2014) DOI: 10.1126/science.1260556
  2. Z. Novotný, et al., Ordered Array of Single Adatoms with Remarkable Thermal Stability: Au/Fe3O4(001). Physical Review Letters 108, 216103 (2012) DOI: 10.1103/PhysRevLett.108.216103
  3. R. Bliem, et al., Cluster Nucleation and Growth from a Highly Supersaturated Adatom Phase: Silver on Magnetite, ACS Nano 8, 7531s7537 (2014) DOI: 10.1021/nn502895s
  4. G.S. Parkinson, et al., Carbon monoxide-induced adatom sintering in a Pd–Fe3O4 model catalyst. Nature Materials 12, 724-728 (2013) DOI: 10.1038/NMAT3667
  5. R. Bliem, et al., An Atomic Scale View of Metal-Assisted Redox Reactions on a Pt-Fe3O4 Model Catalyst, Angewandte Chemie Int. Ed., 44, 13999-14002 (2015). DOI: 10.1002/anie.201507368