Connell et al, J. Phys. Chem. Lett . 1 , 3360 (2010)

1. Size and Composition Tunable Nanowire Catalysts Lincoln J. Lauhon, Northwestern University, DMR 1006069 Reducing the size of semiconductor-based devices and finding new ways to make small devices more cheaply supports innovation and enables new applications that can improve quality of life. We have discovered a new approach to make metal catalyst nanoparticles that that may improve control over doping during the bottom-up growth of semiconductor nanowires. The rate of incorporation of dopant atoms, used to make p-n junctions at the heart of many devices, is very sensitive to the phase and composition of the catalyst particle used to grow the nanowire. Our demonstration of size and composition controlled metal alloy nanoparticles provides new degrees of freedom in materials growth. Size and composition controlled Au-Cu alloy nanoparticles (top, middle) were synthesized and used to grow Ge nanowires (right, bottom left). Connell et al,J. Phys. Chem. Lett. 1, 3360 (2010)

2. Atom Probe Tomography of Dopants in Nanowires Lincoln J. Lauhon, Northwestern University, DMR 1006069 Lawrence Crosby, an undergraduate student from Stanford University, participated in the project with the support of the Summer Research Opportunities Program. Together with graduate student Justin Connell, Lawrence analyzed the dopant distribution in Ge nanowires and thin film control samples using atom probe tomography. In addition to receiving training on this advanced analytical instrument, Lawrence developed advanced statistical analyses of the atom probe data. MatLab code was written to generate correlation histograms of mass-to-charge spectra from raw data to better quantify dilute impurities. Justin Connell and Lawrence Crosby next to LEAP instrument.