Control of Lattice Disorder and Growth Morphology in ZnGeN 2 Kathleen Kash, Case Western Reserve University, DMR It had been speculated, in a 2008 article by this group on Raman scattering in single crystal ZnGeN 2, that the striking observation of strong density-of-states features, indicating relaxation of translational symmetry, along with strong Raman peaks, which indicated preservation of translational symmetry, may have been due to Zn-Ge exchange defects. This work supports that earlier speculation, showing that the degree of ordering, as measured by x-ray diffraction, correlates with the emergence of density-of-states features and the sup- pression of Raman peaks, and can be controlled by growth conditions. This work shows that the anisotropy in growth rates can also be controlled with growth conditions, producing morphologies varying from thin platelets to long, hexagonally faceted “needles”. This work is an important step in the understanding and control of properties of this and other II-IV-nitride semiconductors, from the effects of exchange defects on band structure to transport properties. Electron microscope images of ZnGeN 2 crystals grown under different conditions, with shapes varying from “needle-like” to “platelets”. Blanton, He, Shan and Kash, MRS Proceedings 1493, (2013) doi: /opl

Photoluminescence and Excitation Spectroscopy of ZnSnN 2 Kathleen Kash, Case Western Reserve University, DMR The Zn-IV-nitride semiconductors are gaining increasing scrutiny for both their interesting similarities to, and important differences from, the important III-nitrides GaN, AlN, and InN. While ZnGeN 2 and ZnSiN 2 were first synthe- sized in 1970, it was not until 2011 that the low-bandgap member of this family, ZnSnN 2, was reported. The material has now been grown by three different methods. Our near- equilibrium, vapor-liquid-solid growth has produced material of sufficiently high quality to emit light, allowing measurement, by photoluminescence excitation spectroscopy, of a band gap of 1.7 ± 0.1 eV. The photolum- inescence efficiency at room temperature was shown to be independent of excitation intensity over the range 10 3 to 10 8 W/cm 2. The growth of high quality material is critical for the accurate measurement of physical properties. P.C. Quayle, K. He, J. Shan, K. Kash, MRS Commu- nications FirstView, doi: /mrc (2013) Photoluminescence (red) and photolumin- escence excitation (PLE-black) spectra of poly-crystalline ZnSnN 2. Empty symbols; PLE signal from spectral region 1. Filled symbols; PLE signal from spectral region 2.

The 5 th Annual Midwest Conference for Undergraduate Women in Physics Kathleen Kash, Case Western Reserve University, DMR This conference was one of six held simultane- ously in (The five others were held at the University of Washington, Yale, Texas A&M University, the University of Tennessee, and Stanford.) Kash served as PI on the proposal to the NSF for support of these five conferences. This proposal was the first to incorporate support for a social sciences expert (Prof. Gayle Buck, Indiana University) to gather and analyze data on the effectiveness of these conferences. Kash also served as faculty mentor for the six CWRU senior physics and astronomy majors, pictured at left, who comprised the organizing committee for the CWRU conference. These students, all but one of whom are currently pursu- ing graduate studies, worked for almost one full year on this project. Despite unavoidable cancel- lations due to a heavy snowstorm that hit the Midwest the evening before its start, the two-day conference hosted 120 participants from 43 insti- tutions. Top: the organizing committee; undergraduates Kimberly Star, Elizabeth McNany, Lauren Nicholson, Chelsea Spengler, Rebecca Gilson, and Jessica Hatch at the conference dinner held at the Cleveland Museum of Natural History. Bottom: session on graduate school; panel composed of graduate students from several institutions.

Electronic and Photonic Materials Research Education and Outreach Kathleen Kash, Case Western Reserve University, DMR Research projects of three Physics Ph.D. students and two undergraduate physics majors, one underrepresented minority student, were supported this year. Undergraduates drive their own projects early on in their research, usually from the design stage through fabrication, synthesis and charac- terization. These students benefit from an unusual opportunity for independence while also working closely with faculty (Prof. Kash at CWRU and Prof. Jeff Dyck at John Carroll University) and graduate student mentors, preparing them well for research in graduate school. Prof. Kash participates each year in “Introduce a Girl to Science Day”, an annual event organized and run at CWRU by the undergraduate- and graduate-student organization “Women in Science and Engineering Roundtable (WiSER)” for middle- school girls from Cleveland-area, predominantly minority institutions. This year she organized the outreach activity “Making Lightning; Fun with Electricity and Magnetism”. Image caption Top: students performing a growth experiment using a nitrogen plasma. Bottom; students assembling a new growth instrument.