We demonstrate anomalous gaseous field ionization and field desorption on branching intrinsic silicon nanowires
grown by a two-step VLS technique. Field ionization and desorption I-V curves of argon, nitrogen, helium, and
ammonia, were recorded individually within a wide pressure range (10-7 to 10 Torr). Field ionization initiated at sub
volt was followed by field desorption at about 7 - 38 V (applied field of ~ 7×102 to 3.8×103 V/cm). Such voltages
are three orders of magnitude smaller than the applied voltages required to generate field ionization on sharp
metallic tips having the same tip curvature. The measured I-V curves were pressure dependent. Low voltage filed
ionization and desorption phenomena were attributed to the combination effects of geometrical field enhancement
on the apex of nanoscale silicon branches, field penetration, increased tunneling critical distance, band gap widening
due to quantum confinement, and the surface states formed by the catalyst. The results presented herein suggest that
gold terminated branching silicon nanowires could be strong candidates in building low power gas ionization
sensors useful in highly selective detection of gases with low adsorption energies.
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