Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 99: Scanning Probe Methods III

O 99.3: Vortrag

Freitag, 4. April 2014, 11:00–11:15, GER 38

Electron-phonon coupling of hot and low-energy electrons studied with SP-STM — •Anika Schlenhoff, Stefan Krause, and Roland Wiesendanger — Institute of Applied Physics, University of Hamburg

Heat dissipation in electronic devices influences their performance and reliability. As dimensions approach the nanoscale, understanding thermal phenomena on a local scale becomes crucial. In spin-polarized scanning tunneling microscopy (SP-STM) the atom-size probe tip allows for a very local current injection. By changing the tip-sample distance, the current can be varied by orders of magnitude.

In our experiments, we inject low-energy tunneling electrons at U = 200 mV and hot field-emitted electrons at U = 5 V into a superparamagnet, consisting of about 50 iron atoms on a W(110) substrate [1]. In both cases, increasing the current significantly rises its thermal switching frequency, indicating considerable Joule heating. Astonishingly, for the same power a lower effective temperature increase of the nanomagnet is observed for the hot field-emitted electrons. Our experiments reveal that the Joule heating depends not only on the power but also on the electron energy. The results will be discussed in terms of different relaxation mechanisms for the respective electron energies. Within a simple model taking the heat flow from the nanomagnet to the substrate into account [2], we quantify the electron-phonon coupling for the hot and the low-energy electrons.

[1] A. Schlenhoff et al., Phys. Rev. Lett. 109, 097602 (2012).

[2] W. A. Little, Can. J. Phys. 37, 334 (1959).