Electrostatic tip effects in scanning probe microscopy of nanostructures.

Area of Science:

• Materials Science
• Nanotechnology
• Physics

Background:

• Electrical scanning probe microscopies (SPM) are vital for nanoscale semiconductor characterization.
• The metallic tips used in SPM are not passive and can induce local band bending, complicating quantitative analysis.
• Tip-induced band bending (TIBB) effects are sensitive to local geometry and material properties.

Purpose of the Study:

• To investigate the impact of TIBB on charge reorganization in nanoscale semiconducting materials.
• To quantify the influence of confined geometries, such as nanowires, on TIBB.
• To improve the interpretation of electrical SPM measurements by incorporating TIBB effects.

Main Methods:

• Sequential finite element simulations were employed to model charge reorganization due to TIBB.
• Simulations explored both planar and nanostructured geometries.
• Experimental validation was performed using in operando scanning microwave impedance microscopy on silicon nanowire devices.

Main Results:

• TIBB significantly alters carrier depletion and accumulation in confined geometries compared to bulk materials.
• Finite size effects, related to the Debye length, drive this charge reorganization in nanostructures.
• The model incorporating TIBB accurately explains experimental contrast variations observed at p-i junctions in silicon nanowires.

Conclusions:

• Accurate interpretation of electrical SPM measurements necessitates the inclusion of TIBB.
• TIBB is particularly critical for analyzing weakly screening, low-doped, or complex nanoscale systems.
• Understanding TIBB is essential for advancing the characterization of semiconductor nanostructures.