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Nanowire Doping via Monolayer Doping

Nanowire Doping via Monolayer Doping. Patrick Bennett, AS&T. Ho, et. al. Nature Materials 7 , 62-67 (2008). Motivation. Ions have sufficient energy to pass through a nanowire without stopping, yet still causing serious lattice damage.

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Nanowire Doping via Monolayer Doping

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  1. Nanowire Doping via Monolayer Doping Patrick Bennett, AS&T Ho, et. al. Nature Materials7, 62-67 (2008)

  2. Motivation • Ions have sufficient energy to pass through a nanowire without stopping, yet still causing serious lattice damage. • Spin on techniques lack control and uniformity at the nanoscale. Ho, et. al. Nature Materials7, 62-67 (2008)

  3. Process Outline • Process carried out in glove box in N2 environment Ho, et. al. Nature Materials7, 62-67 (2008)

  4. Results X-Ray Photoelectron Spectrometry (24 Hrs elapsed) • Low amount of post deposition oxidation (inset unreacted substrate) • Dopant profile similar to conventional techniques (limited source) • Observed self limiting surface reaction for both P (Diethyl 1-propylphosphonate) and B (allyboronic acid pinacol ester) dopants Si-C bond Si-O bond Ambient exposure Ho, et. al. Nature Materials7, 62-67 (2008)

  5. Results, continued • 33% efficiency of Boron doping (deduced from theoretical coverage and sheet resistance). Cut in half without capping. • 95% efficiency for Phosphorus. Due to decreased diffusivity of P in SiO2 • RS std. dev. across sample: 2-5% • High reproducibility B P Ho, et. al. Nature Materials7, 62-67 (2008)

  6. Dose Modulation Reduction of Binding sites for precursor • Mixed solution of blank (dodecene) and dopant (B) precursors • Equivalent five and twentyfold decrease in dose suggests similar surface reactivity Tunability of doping via precursor structure • Footprint of precursor molecule governs surface concentration • 6x reduction in dose using trioctylphosphine oxide (TOP) over DPP 6x footprint Ho, et. al. Nature Materials7, 62-67 (2008)

  7. Nanowires • Proof of concept: 2 terminal device (back gated) • Ohmic contacts formed with DPP • n-type switching obtained with TOP(400x enlargement??) • ION/IOFFratio of 103 • 1D doping profile not modeled. • Applied with more success to ultrathin SOI substrates (data not shown) Ho, et. al. Nature Materials7, 62-67 (2008)

  8. Summary • Novel doping technique • Highly controllable in bulk • Proof of concept, successfully doped nanowires • Carried out in restrictive environment, but not in vacuum (except for capping in e-beam evaporator) • Very shallow junction depth • Poor control over nanowire doping (expect more papers soon I’d assume) Comments Ho, et. al. Nature Materials7, 62-67 (2008)

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