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UU2.06 - A Rigorous Analysis of Image Force Barrier Lowering in Metal-Semiconductor Nanowire Contacts 
April 22, 2014   4:00pm - 4:15pm

Image force barrier lowering is an important effect in metal-semiconductor contacts. In planar systems it is well understood and acknowledged-for when discussing semiconductor device properties. However, in regards to semiconductor nanowire devices, reports dealing mainly with this effect are scarce - both experimental and theoretical. Herein, we introduce a rigorous treatment of this problem taking into account image potential inside closed geometries; this includes combining the image force electrostatic potential with the band diagram of the closed geometry - a task which is trivial when considering large planar systems. Conversely, when considering closed geometries, aside from calculating the image force, the derivation of the barrier lowering requires an additional calculation - a reference energy for the charge at the geometry center. We approach the problem from a fundamental point of view and discuss spheres as well as cylinders. Furthermore, although the governing expressions are complex and can only be evaluated numerically, we present analytical approximations for the cylindrical system, which allow easy implementation in band-diagrams. The results are then used to calculate the image force barrier lowering of metal wrapped cylindrical nanowires. Calculations show that the effect is generally stronger than that of planar systems, however system dimensionality may induce non-trivial effects.We believe that this study is of major interest to the nanowire community, and in particular for the analysis of nanowire I-V measurements where wrapped or omega-shaped metallic contacts are involved.

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