High-resolution detection of Au catalyst atoms in Si nanowires

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The potential for the metal nanocatalyst to contaminate vapour–liquid–solid grown semiconductor nanowires has been a long-standing concern, because the most common catalyst material, Au, is highly detrimental to the performance of minority carrier electronic devices. We have detected single Au atoms in Si nanowires grown using Au nanocatalyst particles in a vapour–liquid–solid process. Using high-angle annular dark-field scanning transmission electron microscopy, Au atoms were observed in higher numbers than expected from a simple extrapolation of the bulk solubility to the low growth temperature. Direct measurements of the minority carrier diffusion length versus nanowire diameter, however, demonstrate that surface recombination controls minority carrier transport in as-grown n-type nanowires; the influence of Au is negligible. These results advance the quantitative correlation of atomic-scale structure with the properties of nanomaterials and can provide essential guidance to the development of nanowire-based device technologies.

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Figure 1: Aberration-corrected STEM imaging of Au atoms in a phosphorus-doped Si nanowire.
Figure 2: Three-dimensional localization of Au atoms.
Figure 3: Atom probe analysis of the catalyst–nanowire interface.
Figure 4: Electron beam induced current measurement on Si nanowire devices.
Figure 5: Dependence on diameter of minority carrier diffusion length.


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The work at Northwestern was supported by the National Science Foundation (NSF) through the Materials Research Science and Engineering Center (MRSEC) (J.A.), CAREER (L.L.), NIRT (E.H.) and Graduate Research Fellowship (J.L.) programmes; the Office of Naval Research and a Ford Foundation Fellowship (D.P.); and an Alfred P. Sloan Research Fellowship (L.L.). E.H. acknowledges a travel grant from the Northwestern University Nanoscale Science and Engineering Center (NSEC). We acknowledge the Northwestern University Center for Atom -- Probe Tomography facility and the Northwestern University Atomic- and Nanoscale Characterization Experimental Center (NUANCE). The NUANCE Center is supported by NSF-NSEC, NSF-MRSEC, the Keck Foundation, the State of Illinois and Northwestern University. The work at Birmingham and Daresbury was supported by the Engineering and Physical Sciences Research Council.

Author information

J.A. and E.H. contributed equally to this work. J.A. performed the device experiments and analysed the data with L.L. D.P. performed the atom probe experiments and analysed the data with L.L. E.H. and J.L. synthesized the materials. The STEM work and analysis were conducted by the Birmingham-SuperSTEM collaboration (Z.Y.L, F.Y, R.E.P., M.H.G., P.W. and A.L.B.) in association with the Northwestern group (E.H. and L.L.). L.L. coordinated the design and execution of the experiments. J.A. and L.L. co-wrote the paper. All authors discussed the results and commented on the manuscript.

Correspondence to Lincoln J. Lauhon.

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