Rational Synthesis and Doping of Semiconductor Nanowires for Transport Imaging Roya Maboudian, University of California-Berkeley, DMR 0804646.
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Rational Synthesis and Doping of Semiconductor Nanowires for Transport ImagingRoya Maboudian, University of California-Berkeley, DMR 0804646
Single-crystal SiC and Si nanowires (NWs) have been synthesized by vapor-liquid-solid (VLS) growth with controlled doping to study their unique electronic and thermal contact/transport properties via imaging techniques. Ex situ doping, followed by high temperature annealing achieves active dopant concentrations in Si NWs > 1019 cm-3 (as indicated by Fano resonance of the Stokes optical Raman peak) with unchanged morphologies according to scanning electron microscope (SEM) images. Si NWs have been synthesized through VLS growth catalyzed by more CMOS compatible Pt as a point of comparison against typical Au-catalyzed VLS Si NWs. Combined with our recent Raman spectrometrymeasurements of the temperature dependence of optical phonon frequencies in individual Si NWs , these results enable scanning confocal Raman spectrometry and electron-beam-induced current (EBIC) studies on electronically contacted individual nanowires with various catalysts and doping combinations that give direct insight into their electronic and thermal behavior.
A: Assymmetric Raman optical phonon peak due to Fano resonance in Si NWs indicates acceptor levels > 1019 cm-3 from ex-situ doping (Inset scale bars = 2 μm). B: Pt-catalyzed VLS-grown Si NWs (Scale bar = 5 μm). C: The linear temperature dependence of the optical phonon frequency (-dω/dT) for single Si NWs down to 33 nm diameter closely matches that for bulk Si.
 Doerk, Carraro, Maboudian, Phys. Rev. B 80, 073306 (2009)
PI Roya Maboudian and graduate student Greg Doerk have worked with two undergraduate women to encourage their ongoing participation in scientific research. Christine Politi is a University of Colorado undergraduate student who worked with Greg in 2009 as part of a summer REU through the NSF-sponsored Center of Integrated Nanomechanical Systems (COINS). Gabriella Lestari is a UC Berkeley student who has worked with Greg for over a year and has made important contributions to growth and doping of silicon nanowires. Gabriella will be presenting the results of her nanowire growth studies in the Student Paper Competition at the 2009 AIChE National Student Conference. Research efforts including the work of both these students has been disseminated through events open to the public, including a summer REU poster session and a COINS biweekly seminar, and both students’ work will likely be featured in future publications.
U.C. Berkeley undergraduate researcher Gabriella Lestari at work preparing samples for silicon nanowire growth.