Study of a Semiconductor Nanowire under a Scanning Probe Tip Gate

Nanowires are sensitive to external influences such as surface charges or external electric fields. An Atomic Force Microsope (AFM) is modified to perform back gating and tip gating measurements in order to understand the interaction between an external field, and surface charge and nanowire conductance. A 2D finite element method (FEM) model is developed to simulate the measured conductance. The model shows that surface states play a critical role in determining nanowire conductance. A 3D FEM model is developed to examine the influence of the AFM tip on the lateral resolution of the AFM tip in the electrostatic measurement. The radius of the AFM tip determines the lateral resolution of the tip. However, carrier concentration in the nanowire establishes a lower limit on the lateral resolution, for small tip radii. These results enable one to optimize Scanning Probe Microscopy experiments as well as inform sample preparation for nanowire characterization.MAS