1. Heteroepitaxy of Icosahedral Boron Arsenidee James H. Edgar, Kansas State University, DMR 0602807 The epitaxial growth of the icosahedral boron arsenide (B 12 As 2 ) is being optimized so its inherent properties may be established. B 12 As 2 heteroepitaxy on silicon carbide substrates is refined to improved its morphology and structure. An indirect band gap of 3.9 eV and the room temperature hole mobility of 10-20 cm 2 /V·s was measured. These properties are encouraging, as they suggest this wide band gap semiconductor is potentially useful in high efficiency neutron detectors and nuclear-to- electrical energy conversion devices, i.e. betavoltaic cells. Optical micrographs: unoptimized (top) and optimized (bottom) conditions produce B 12 As 2 films with rough and smooth morphologies, respectively. Scale bars are 50 microns.

2. Inspiring Interest in Materials Science and Engineering by Crystal Analysis and Growth James H. Edgar, Kansas State University, DMR 0602807 Workshops on crystal growth and the applications of crystals were held for the Girls Researching our World (GROW) for girls age 12 to 14, and for high school students through the Engineering and Science Summer Institute (ESSI). These programs encouraged young women to consider college education and careers in science and engineering. Student did experiments on elements of symmetry, crystal growth and nucleation and learned about the importance of crystals in the semiconductor and optoelectronics industries. (Left) A student is surprised by the fast crystallization from a superstaturated sodium acetate solution after a seed crystal is added. (Right) The girls rush to look at their borax crystals after a night of crystal growth.

3. Single-crystalline B12As2 on m-plane „11¯00… 15R-SiC Hui Chen,1,a Guan Wang,1 Michael Dudley,1 Zhou Xu,2 J. H. Edgar,2 Tim Batten,3 Martin Kuball,3 Lihua Zhang,4 and Yimei Zhu4 1Department of Materials Science and Engineering, Stony Brook University, Stony Brook, New York 11794, USA 2Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506, USA 3H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom 4Center for Functional Materials, Brookhaven National Laboratory, Upton, New York 11973, USA Received 10 May 2008; accepted 24 May 2008; published online 13 June 2008 Single crystal, heteroepitaxial growth of icosahedral B12As2 IBA, a boride semiconductor on m-plane 15R-SiC is demonstrated. Previous studies of IBA on other substrates, i.e., 111Si and 00016H-SiC, produced polycrystalline and twinned epilayers. In contrast, single-crystalline and untwinned IBA was achieved on m-plane 15R-SiC. Synchrotron white beam x-ray topography, Raman spectroscopy, and high resolution transmission electron microscopy confirm the high quality of the films. High quality growth is shown to be mediated by ordered nucleation of IBA on 474 substrate facets. This work demonstrates that m-plane 15R-SiC is a good substrate choice to grow high-quality untwinned IBA epilayers for future device applications. © 2008 American Institute of Physics. DOI: 10.1063/1.2945635 Icosahedral boron arsenide B12As2 IBA is a wide band gap semiconductor 3.47 eV with the extraordinary ability to “self-heal” radiation damage. This makes it an attractive choice for devices exposed to radiation which can severely degrade the electrical properties of conventional semiconductors, causing devices to cease functioning. Among the particularly intriguing possible applications for IBA are beta cells, devices capable of producing electrical energy by coupling a radioactive beta emitter to a semiconductor junction, another space electronics.1–8 IBA is based on 12-boron-atom icosahedra, which reside at the corners of an –rhombohedral unit cell, and two- atom As–As chains lying along the rhombohedral 111 axis.1,5 In the absence of native substrates, IBA has been heteroepitaxially grown on substrates with compatible structural parameters. To date, this has been attempted on substrates with higher symmetry than IBA such as Si and 6H-SiC.5,7–11 James H. Edgar, Kansas State University, DMR 0602807