Novel Microscopies Research

The optimization of the nucleation and epitaxial growth of wide bandgap semiconductors using non-thermal, controlled-energy growth precursors, and the growth and characterization of sputtered magnetic superlattices are major materials research areas at Ohio University. Characterization of these materials in situ is primarily through direct imaging methods including several forms of emission microscopy and with photoelectron diffraction. Pioneering efforts in the use of microscopy in materials characterization have been made by Ohio University researchers, in particular the development of compact emission microscopes for UHV real-time material characterization during growth (Kordesch) . Direct Imaging Methods: Two photoelectron emission microscopes (PEEM), a thermionic emission microscope and a low energy electron microscope (LEEM) with in situ capabilities and controlled energy deposition sources (a seeded supersonic molecular beam, a discharge radical and metastable source, and a cold cathode low energy ion source) are already in use to optimize the growth of the wide bandgap semiconductors. In practice, the materials of interest (diamond GaN, AlN, cBN) cannot be structurally equilibrated, either due to undesirable structure transitions that are more favorable at the growth temperature, or because the mobility of the constituents is limited. The direct measurement of reactant mobility and transport of the growth species, in situ, in real time will be used to optimize growth. Emission microscopy is a high contrast method that is able to detect surface layers as little as .001 monolayer thick, and lateral dimensions on the order of 100 nm. It is best applied where the trade-off between resolution and contrast can be made in favor of image contrast and image acquisition rate. The dynamical behavior of these layers can often be observed in real-time, in situ, with emission microscopy.   Professor Smith is a pioneer on Atomic Force Microscopy  (AFM) and Scanning Tunneling Microscopy (STM); especially applications to wide gap nitride semiconductor surfaces. His research was recently featured on the cover of the jounal Science.   Associated Faculty: Kordesch, Smith