“God made solids, but surfaces were the work of the devil.” Wolfgang Pauli
Our surface group aims to understand chemical and physical processes that occur at the solid-vacuum interface and in thin-films grown on surfaces or exfoliated from bulk materials. In particular, we are interested in the interplay between the morphology and electronic structure of nano-structured surfaces. We are also interested in surface chemistry and catalysis. We study a variety of materials including exfoliated and epitaxially grown graphene, single crystal metals, both flat and decorated with nano-scale step arrays
We employ a variety of experimental techniques such as Scanning Tunneling Microscopy (STM), Temperature Programmed Desorption (TPD), Angle Resolved PHotoemission Spectroscopy (ARPES) and Low Energy Electron Diffraction (LEED).
If the last 50 years of science and technology have been the era of semiconductors, it can be argued that increasingly the techniques and solid-state interest in these materials is now turning toward complex oxides and their properties. These oxide materials offer a variety of striking functionalities associated with subtle changes in their order parameters, which may be tuned with adjustment in composition and phase. Thus to take one such crystal type, i.e. strontium titanate: groups have reported that exhibits metal-insulator transitions, ferroelectric effects, 2D electron gases at heterointerfaces, stress-induced transitions, and superconductivity.
This rich array of properties has opened the door to an explosive growth in the materials science and preparation of these crystals. Thus methods such as MBE, ALD, CVD, and PLD have all been explored and in many cases shown to yield high-quality crystal growth, despite the challenges of maintaining epitaxy or compositional uniformity. In addition, nanoscale complex-oxides crystals have also been prepared using chemical colloidal growth techniques that were earlier applied to formation of semiconductor materials.
Despite these advances in growth, there remains a wide variety of new thin film and patterning techniques to be explored for these oxide materials – particularly capable of nanometer-scale spatial resolution. The importance of the oxide interfaces for these methods further emphasizes the need for careful investigation of the surfaces of such structures. Recently work in Professor Osgood’s and his collaborators labs, has demonstrated the initial stages of understanding and controlling the chemistry of oxides both in nanoscale and in thin film form. These developments allow for control over the processing environment for oxides. A part of Prof. Osgood’s research is focused on investigating the materials chemistry for nanoscale patterning of an oxide surface. It makes use of a striking chemical phenomenon that may act on an oxide surface after mild ion bombardment, namely buried-cluster control of local strain on the surface of an oxide crystal and its role in mediating local surface reactions.