Characterizing defects and transport in Si nanowire devices using Kelvin probe force microscopy

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Silicon nanowires (Si NWs) are crucial for advanced electronic devices.
• Understanding their electronic structure and defects is vital for performance optimization.
• Field effect transistor (FET) device structures provide a platform for NW characterization.

Purpose of the Study:

• To characterize Si NWs fabricated using different methods (RIE and VLS).
• To identify defects and impurities affecting the electronic properties of Si NWs.
• To evaluate the effectiveness of KPFM in nanoscale device characterization.

Main Methods:

• Fabrication of Si NWs using Reactive Ion Etching (RIE) and Vapor-Liquid-Solid (VLS) growth.
• Characterization using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and Scanning Kelvin Probe Force Microscopy (KPFM).
• Analysis of surface electronic structure and electrical contact properties.

Main Results:

• RIE NWs exhibit surface contaminants and voltage-dependent defects indicating impurity states.
• VLS NWs show gold (Au) impurity states in the bandgap, even after purification.
• KPFM reveals poor electrical contacts (nanogaps, short circuits) in VLS NWs not seen by AFM or I-V measurements.

Conclusions:

• Defects and impurities significantly influence the electronic behavior of Si NWs.
• KPFM offers unique insights into surface potential and electrical contact issues in nanoscale devices.
• A systematic characterization method is established for nanoscale systems under operational conditions.