STUDIES OF ULTRAFAST CARRIER DYNAMICS

For studies of ultrafast carrier dynamics of semiconductors THz spectroscopy is an ideal method since the plasma frequency of these typically falls within the THz range. Material properties like the electrical conductivity, refractive index, and carrier mobility can be extracted from a THz spectroscopy experiment, and this contact-free characterization method is highly attractive for semiconductor devices and studies of new 2D materials such as graphene, where having a physical probe attached to the sample is impractical.

THz SENSING OF CRYSTALLINE MATERIALS

Compared to conventional IR spectroscopy, THz radiation excites both intra- and intermolecular modes in crystalline materials and hence, gives a more precise identification of the material itself as well as its chemical composition. To increase the sensitivity for measuring a specific chemical, THz resonant array structures can be implemented in a THz spectroscopy setup. For specific designs of the array structure the sensitivity for compounds such as sucrose, fructose, riboflavin, RDX or testosterone can be enhanced by orders of magnitude.

SUBWAWELENGTH THZ MICROSCOPY

A general problem with THz light is that the long wavelengths limit the spatial resolution of THz imaging systems to several hundreds of micrometers. However, the diffraction-limit can be “beaten” with various methods such as using near-field probes pushing the spatial down to the micro- or even nanoscale. Our research group studies ultrafast carrier dynamics in semiconductors and vibrational spectroscopy in crystalline materials with THz technology. Using near-field probes and THz emission microscopy we are able to study THz phenomena with a spatial resolution on the microscale. A particular area of interest is solar cell materials such as perovskites since these tend to for grain structures. Knowing the carrier transport across the grain structure is important for the functionality of the solar cell.