First-Principle Modeling for Low-Energy Electron MicroscopyKarsten Pohl, University of New Hampshire, DMR 1006863 Low-energy electron microscopy (LEEM) is an important analysis technique for imaging surface structure in real space. We have developed a wave-matching method to calculate the LEEM spectra using the self-consistent wave functions from density-functional supercell calculations. In contrast to traditional multiple scattering analysis, our approach is not limited by spherically symmetric atomic potentials, which are not suitable for very low energy electrons in directionally bonded materials. We have demonstrated that our wave-matching method reproduces the quantum size oscillation in the LEEM spectra of fee-standing few-layer graphene (FLG) without any fitting parameters. The quantum size oscillation in FLG systems has become instrumental in determining the thickness of the FLG films. Calculated LEEM spectra for free-standing few-layer graphene (1 -- 7 layers from bottom to top) using the wave-matching method. The curves are vertically shifted for visibility.
Nanotech in every classroom through K-12 teacher trainingKarsten Pohl, University of New Hampshire, DMR 1006863 In order to bring some basic understanding of the physical phenomena behind many the new fascinating nano-gadgets to the K-12 classroom, our group is heavily engaged in the work with K-12 teachers from the state of New Hampshire and southern Maine. We are also frequently visiting schools and host students in our nano-science lab on campus. Graduate students, Amanda Brown, hosted a 2-week nano-tech camp for middle school girls – our Engineeristas in July 2011 in collaboration with NH EPSCoR, while Jun Wang in helping REU students study the connection behind the molecular structure of pentacene derivatives and their surface adsorption structure with help of the scanning tunneling microscope (STM) and our newly adopted computer modelling capabilities. K-12 teachers, at a Nanotechnology workshop at UNH on April 11, 2012, engaged in a discussion about the workings of a super-microscope - the STM, which allows them to ‘see’ individual molecules as they self-assemble into novel nanostructures.