| AVS 54th International Symposium | |
| Surface Science | Tuesday Sessions |
| Session SS2-TuM |
| Session: | Surface Structure and Growth on Metals |
| Presenter: | C.G. Tao, The University of Maryland, College Park |
| Authors: | C.G. Tao, The University of Maryland, College Park W.G. Cullen, The University of Maryland, College Park E.D. Williams, The University of Maryland, College Park S.E. Hunyadi, The University of South Carolina C.J. Murphy, The University of South Carolina |
| Correspondent: | Click to Email |
Semiconducting and metallic nanowires have been the subject of intense research efforts for their potential applications in nanoscale electrical circuits and chemical sensors. For all the applications, and especially for sensors, the morphological and thermodynamic nature of the nanowire surfaces, including the presence of defects like steps and twin boundaries, play a crucial role in the functional response. Even though there have been many demonstrations of nanowire applications, extremely few studies directly address the issues of cleanliness and structural morphology of the surfaces of nanowires at the atomic scale. Here we will present the surface morphology and thermodynamic properties of Ag nanowires, characterized by scanning tunneling microscopy (STM) at room temperature. The Ag nanowires were prepared via a seedless, surfactantless wet chemical synthesis process and suspended in water. They then are redispersed into methanol by centrifugation, and are deposited onto atomically clean Ag thin films in ultra-high vacuum via a solution deposition method. By gently annealing the samples, methanol on the substrate and the surfaces of Ag nanowires is removed. The STM topography images reveal the facets of the penta-tetrahedrally twinned crystals which constitute the Ag nanowires, and sawtooth features of the boundaries of neighboring twinned crystals. On the facets, frizzy monatomic steps and rectangular shapes monolayer islands are clearly observed. Using a dynamic STM scan method, we obtain quantitative properties of step fluctuations, which are governed by periphery diffusion. Combing previous density functional theory (DFT) calculations and dynamics studies on low-index faces of Ag, we propose that the side facets are Ag(100) surfaces. Related studies about the time evolution of the twin boundaries and how the surface defects are associated with the electrical current flowing through the nanowires will also be discussed. --Supported by the NSF MRSEC (DMR 05) at the University of Maryland.