Short annotation: Time-resolved terahertz spectroscopy utilizes ultrashort far infrared pulses as a contact-free probe of ultrafast response of photoexcited samples. In semiconductor materials and structures the response is related namely to the charge carrier transport on a 5–50 nm length scale. Detailed analysis of the spectra and theoretical simulations of the charge carrier motion allow one to obtain the nanoscopic response function of mobile carriers in a given sample with a sub-picosecond time resolution. This work will contribute to the fundamental understanding of the charge carrier transport in nanosystems on picosecond time scale. It will focus on experimental and theoretical research of selected nanostructured systems by means of THz spectroscopy and numerical simulations. The results of this work may find applications e.g. in photovoltaics.
Description
Open PhD. position, conditions: work with the THz group, Institute of Physics, Prague, Czech Republic PhD. degree from the Charles University, Prague supervisor: P. Kuzel Scholarship in the frame of a Marie-Curie initial training network; conditions: living allowance about 1950 Euro /month + mobility allowance for 3 years. Starting date: as soon as possible. Annotation: Time-resolved terahertz spectroscopy utilizes ultrashort far infrared (typically 0.1–3 THz) pulses as a contact-free probe of ultrafast response of photoexcited samples. In semiconductor materials and structures the response is related namely to the charge carrier transport on a 5–50 nm length scale. The measured photoconductivity spectra then depend namely (1) on interaction of the carriers with nanostructure boundaries (localization of charge) and (2) on depolarization fields which strongly build up in inhomogeneous conducting media. Detailed analysis of the spectra and theoretical simulations of the charge carrier motion allow one to obtain the nanoscopic response function of mobile carriers in a given sample with a sub-picosecond time resolution. This work should contribute to the fundamental understanding of the charge carrier transport in nanosystems. The student will focus on experimental and theoretical research of selected nanostructured systems (e.g. isolated InGaAs and GaAs islands, nanocrystalline films of CdSe, Si nanowires) by means of THz spectroscopy and numerical simulations. Experiments and simulations will be carried out as a function of temperature and especially as a function of the optical excitation density (assessment of the depolarization fields). The main goal of the work is to gain a deeper insight into the nanoscale charge transport and its relation to the THz conductivity spectra. The results of this work may find applications e.g. in photovoltaics. The PhD. student will learn: work with femtosecond laser systems, nonlinear optics (second and third harmonic generation, parametric amplification), optical pump – terahertz probe spectroscopy (method, setup adjustment), effective medium theories in photoexcited media, Monte-Carlo simulations of charge carrier dynamics. Basic reviews and books on the topic: R. Ulbricht, E. Hendry, J. Shan, T. F. Heinz, and M. Bonn: Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy, Rev. Mod. Phys., 83, 543 (2011) J. Lloyd-Hughes, T-I. Jeon: A review of the terahertz conductivity of bulk and nano-materials, J. Infrared Milli. THz. Waves, 33, 871 (2012) H. Němec, P. Kužel, and V. Sundström: Charge transport in nanostructured materials for solar energy conversion studied by time-resolved terahertz spectroscopy, J. Photochem. Photobiol. A 215, 123 (2010) C. Jacoboni, Theory of E
Benefits
work in a well-established THz spectroscopy group PhD. degree from the Charles University, Prague
Additional Job Details
web site of the group http://lts.fzu.cz