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1. Self-Assembly of Silver Nanowires on Silicon Substrates James H. Craig, Jr. DMR-0511811 Fig. 2 SEM image Ag nanowires on Si(001) * One of the projects in the proposal, “Issues in Thin Film Growth on Group IV Semiconductors,” is the study of Ag nanowires. The objective of this research (performed in collaboration with the University of Duisburg-Essen in Germany) is to understand the physical mechanism that drives the growth of novel wire-shaped metallic islands on silicon surfaces. Nanowires are of interest technologically because of their potential for quantum device applications, and scientifically as they provide a playground for studying the physics of quasi-1D systems. * Figure 1 shows a series of Photo-emission electron microscopy (PEEM) images displaying the self-assembly of a Ag nanowire growing on an atomically clean silicon surface. The different images in the figure are at different times with time increasing from (a) to (c). Interestingly, the width of the growing nanowire remains fixed while the ends of the wire grow without bound. The crystalline shape of the nanowires and compact islands is seen in the Scanning Electron Microscopy image of figure 2. * Figure 3 shows a PEEM image of a silver nanowire during thermal decay. The bright zones at each end of the wire are due to silver atoms being fed onto the surface due to increased temperature. Because the bright zones do not extend from the wires’ side, silver atom diffusion is limited in that direction. We attribute this kinetic limitation to localized Ag-induced step bunching in the vicinity of the growing nanowires, and this effective one- dimensional diffusion is responsible for producing the wire-like islands. (a) (b) Fig. 1 PEEM images of growing Ag nanowire on Si(001) at 600 C Fig. 3 PEEM image of Ag nanowire during thermal decay at 650 C (c)

2. Undergraduate Involvement in Thin Film Research James H. Craig, Jr. DMR-0511811 Undergraduate student Bret Kolditz works on the STM. Undergraduate students Julie Thompson and Steve Yeninas work on the HREELS system. During the summer 2006 eight Bradley University undergraduate physics students participated in this research program mentored by one of the collaborating faculty members supported by the project. Each of these students became proficient at operation of one of the ultra-high vacuum systems in our research group and the associated surface analytical instrumentation. By the end of the ten week summer research period each student group was able to undertake independently the entire process of sample preparation; sample mounting in UHV; system bakeout; data acquisition; and data analysis. The students had the opportunity for "hands on" experience with a variety of instrumentation including: variable temperature UHV scanning tunneling microscope; X-ray and ultra-violet photoelectron spectroscopy; high resolution energy loss spectroscopy; Auger electron spectroscopy; and time-of flight surface mass spectroscopy. During the past year four students have served as presenters at two national meetings- AVS International Symposium in Boston, MA and "Surface Analysis 2006" in Albuquerque, NM. Two undergraduate students have co-authored two publications resulting from work on this NSF project. As a result of these opportunities the participating students have developed impressive research skills far in excess of that which would have been possible from purely classroom activities. Consequently, these students have developed rapidly as enthusiastic and passionate young scientists.