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Shot-noise measurements in graphene

15/03/2012 Mickaël Fay, IN, Grenoble, France

In this talk, I will first give a general introduction to shot-noise which originates from the discrete nature of charge carriers in mesoscopic devices. Shot-noise gives information on the electronic transport that can not be obtained by simple conductance measurements, such as the effective charge of the carriers. Moreover, shot-noise can be used to probe the electronic temperature of mesoscopic systems and it is even possible to use this effect as a primary thermometer. In the second part of my talk, I will focus on recent conductance and shot-noise measurements done on bilayer graphene (BLG) samples at high bias voltages. As a function of bias, we find initially a linear increase of the conductivity, which we attribute to self-heating [1]. At higher bias, the conductivity saturates and even decreases due to backscattering from optical phonons (op). The electron-op phonon (e-op) interactions are also responsible of the decay of the Fano factor at V > 0.1 V. The high-bias electronic temperature extracted from shot-noise measurements goes up to 1200 K at V = 0.75 V. Using the theoretical temperature dependence of BLG conductivity, we extract the electron-op phonon scattering time \tau_e−ph as a function of the bias voltage [2].
[1] J. K. Viljas, A. Fay, M. Wiesner, and P. J. Hakonen, Phys. Rev. B 83, 205421 (2011).

[2] A. Fay, J. K. Viljas, R. Danneau, F. Wu, M. Y. Tomi, J. Wengler, M. Wiesner, and P. J. Hakonen, Phys. Rev. B 84, 245427 (2011)