(Invited) Scan-Probe Microwave Reflectance of Horizontally Aligned Arrays of Single-Walled Carbon Nanotubes: Nanoscale Imaging of SWNT Electrical Properties in the Quantum Regime

Single walled carbon nanotubes (SWNTs) are 1-dimensional nanomaterials with unique electronic properties that make them excellent candidates for next generation device technologies. While nanotube growth and processing methods have progressed steadily, significant opportunities remain in advanced methods for their characterization, inspection, and metrology. We explore the application of nanoscale microwave reflectivity to study SWNT electronic properties. Using Microwave Impedance Microscopy (MIM) and newly developed Microwave Impedance Modulation Microscopy (MIM²), we image horizontal SWNT arrays showing the imaginary part of the reflectivity from nanotubes is dominated by quantum capacitance, a direct probe of SWNT electronic behavior. Microwave imaging offers an extremely versatile "nondestructive" tool for characterization. We reveal the direct correlation of the free carrier density via MIM, the DOS dispersion via MIM², with the nanotube’s structural morphology measured simultaneously via AFM. These techniques offer a new window into CNT physics and could have tremendous impact, enabling optimization of enriched growth processes and post-growth purification, and aiding analysis of device-contact interactions.