Quantitative, nanoscale free-carrier concentration mapping using terahertz near-field nanoscopy

We use ultra-resolving terahertz (THz) near-field microscopy based on THz scattering at atomic force microscope tips to analyze 65-nm technology node transistors. Nanoscale resolution is achieved by THz field confinement at the very tip apex to within 30 nm. Images of semiconductor transistors provide evidence of 40 nm (λ/3000) spatial resolution at 2.54 THz (wavelength λ = 118µm) and demonstrate the simultaneous THz recognition of materials and mobile carriers in a single nanodevice. The mobile carrier contrast can be clearly related to near-field excitation of THz-plasmons in the semiconductor regions. The extraordinary high sensitivity of our microscope provides THz near-field contrasts from less than 100 mobile electrons in the probed volume.