Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Poster I

HL 13.18: Poster

Monday, March 18, 2024, 15:00–18:00, Poster E

Searching for Effective Temperature Seebeck Voltage in Nanoscale Organics — •Anton Kompatscher and Martijn Kemerink — IMSEAM Heidelberg University, Im Neuenheimer Feld 225 69120 Heidelberg

In contrast to inorganics, organic semiconductors usually show a high degree of energetic and structural disorder. While we have relatively good insight into organics as an ensemble of many molecules, the regime of small (few nanometer) length scales, at which relatively few molecules are probed, remains hardly explored. A phenomenon we are especially interested in is the concept of effective temperature wherein a high >10^7 V/m electric field is predicted to generate electron distributions that correspond to much higher temperatures than the lattice temperature. As modeled in a recent publication, the effective temperature should be able to generate exceptionally high Seebeck voltages, which gives us a good option for experimental verification of the theory. In order to generate sufficient field strengths, the use of nanoscale structures, which we fabricate via electron beam lithography, is necessary. The main challenge in analyzing the signal is to separate spurious effects in the experimental system from the Seebeck voltage, which we do by measuring the response to AC voltages and comparing to theoretical predictions. In particular, we exploit the fact that the Seebeck signal should have double the frequency and zero phase lag compared to the input signal. First results are consistent with the generation of finite effective temperatures, which would constitute the most direct proof of the concept so far.