Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 29: Symposium THZ interactions

HL 29.5: Invited Talk

Wednesday, March 28, 2007, 16:15–16:45, H15

Terahertz near-field microscopy — •Roland Kersting¹, Federico Buersgens¹, and Gyu Cheon Cho² — ¹University of Munich, Munich, Germany — ²IMRA America, Ann Arbor, MI, USA

Many efforts in modern semiconductor physics target the integration of nano-objects and one important step towards this goal is the characterization of the nano-materials' electronic properties. Terahertz spectroscopy allows for studying the electronic response directly in the time domain, but the long wavelength of THz radiation (1 THz corresponds to about 0.3 mm) limits the spatial resolution to rather macroscopic scales.

In this contribution we present an apertureless near-field scanning optical microscope (ANSOM) for the THz range, which allows for spatial resolutions down to 150 nm. These extreme subwavelength resolutions are achieved by concentrating the incident THz radiation with a metal tip to a near-field spot, which's diameter is comparable to the tip's apex. The unexpected high image contrast of the THz-ANSOM results from a novel imaging process where the dielectric response of the material shifts the THz resonance of the sampling metal tip. The method is suitable for investigating the dielectric response of electrons in semiconductors. Currently, the sensitivity is sufficient to map as few as 5000 electrons. Further developments in apertureless terahertz microscopy may open up new vistas towards the contactless characterization of electronic quantum states in semiconductors.