Submicron Material Characterization Using Terahertz Scanning Near-Field Microscopy

The recent development of the apertureless terahertz scanning near-field optical microscope (THz-SNOM) allows for submicron spatial resolution [1] and enables a broad variety of novel applications in material characterization. The basic mechanism is that a metallic probe allows for mapping of the THz permittivity of a surface. In this contribution, we report on measurements of microscopic scale charge carrier distributions and dielectric contrast with sub-micrometer resolution in various material systems and structures using THz-SNOM. We have identified a novel imaging mechanism in terms of a configurational resonance [2], which contrasts the widely accepted scattering model at visible and near-infrared frequencies. ~[1] H.-T. Chen, et al., \textit{Appl. Phys. Lett.} \textbf{83}, 3009 (2003). ~[2] H.-T. Chen, et al., \textit{Phys. Rev. Lett.} \textbf{93}, 267401 (2004).