Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 28: Poster Session: Graphen; Transport properties; Transport in high magnetic fields / Quantum Hall effect; Metal-semiconductor hybrid systems

HL 28.10: Poster

Montag, 11. März 2013, 16:00–20:00, Poster A

Phototransmission and Photoconductivity in the THz Spectral Range of Graphene Samples — •Markus Göthlich¹, Fathi Gouider¹, Miriam Grothe², and Georg Nachtwei¹ — ¹Institut für Angewandte Physik, Technische Universität Braunschweig, Mendelssohnstraße 2, D-38106 Braunschweig — ²Physikalisch Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig

Graphene has first been isolated in 2004. Since then this material has become a major field of interest in research, not least due to it’s remarkable Landau quantization E_n = sgn(n) √2 ℏ e v_F² |n| B with n being the Landau level (LL) index. Thus, an intraband transition between LLs with an enery of 10 meV (corresponding to electromagnetic radiation with a frecquency of about 2.4 THz) can theoretically be achieved with a magnetic field as low as 0.2 T. In the case of cyclotron resonance the phototransmission drops and the conductivity of the sample changes due to a change of the carrier density at the Fermi energy. In this contribution, we present the magnetoconductivity and the terahertz (THz) photo-conductivity of devices with graphene. For the photoconductivity measurements, a THz laser system (p-Ge-Laser) is applied. This laser uses transitions between Landau levels of light holes and emits laser impulses in the wavelength range 120 µ m ≤ λ ≤ 180 µ m. The THz laser radiation is used in order to excite charge carriers over the Landau gap. To characterize the examined graphene samples, the Shubnikov-de Haas-effect measurements at a temperature of T = 4 K and in the region of the magnetic fields of 0 ≤ B ≤ 10 T were performed.