Keynote Speaker
Prof. Dr. Lukas Eng
PFM & cAFM – Indispensable Tools when Engineering 2DEGs into Wide-Bandgap Semiconductors
Lukas M. Eng 1,2, E. Beyreuther 1, I. Kiseleva 1, M. Röper 1, E. Singh 1, M. Zahn 1,
and S.D. Seddon 1
1 Institute of Applied Physics, TU Dresden, Nöthnitzerstr. 61, 01187 Dresden, Germany
2 ct.qmat: Würzburg-Dresden Cluster of Excellence - EXC 2147, TU Dresden, Germany
2-Dimensional Electron Gases (2DEGs) in the form of van-der-Waals monolayers or functional interfaces experience widespread interests worldwide for implementations into sensoric applications, both at room (RT) and cryogenic temperatures. Domain walls (DWs) engineered into polar wide-bandgap oxide semiconductors (i.e. into single-crystalline LiNbO3 [1] as shown in this talk) constitute an even superior class of 2DEGs [2,3], since they allow for purposely writing, erasing, reconfiguring, and adjusting such conductive channels at nanometer length scales, notably by applying piezoresponse force (PFM) and conductive atomic force microscopy (cAFM). Moreover, PFM and cAFM decisively contribute to the fundamental understanding of electronic transport along such conductive DWs; cAFM for instance provides the recordings of local-scale IU-characteristics, needed (i) to probe charge injection across Schottky barriers [4], (ii) to quantify the RT hopping-transport activation energy along a single DW [5], or (iii) to delineate the extra DW conductance (DWC) under mechanical strain [6] and photo-illumination [7]. The beauty in DWC engineering comes when reconfiguring these charged DWs in our bulk LiNbO3 single crystals, by applying tip-induced domain switching and 3D PFM [8], hence allowing to purposely engineer Bloch- and Néel-type topological DWs [9] into ferroelectric LiNbO3 as for tuned electronic transport applications.
References:
[1] I. Kiseleva et al., J. Appl. Phys. 138, 034101 (2025); https://doi.org/10.1063/5.0276183.
[2] L.M. Verhoff et al., Phys. Rev. B 6, L042015 (2024); https://doi.org/10.1103/PhysRevResearch.6.L042015.
[3] H. Beccard et al., Phys. Rev. Appl. 20, 064043 (2023); https://doi.org/10.1103/PhysRevApplied.20.064043.
[4] M. Zahn et al., Phys. Rev. Appl. 21, 024007 (2024); https://doi.org/10.1103/PhysRevApplied.21.024007.
[5] Th. Kämpfe et al., Crystal 10, 804 (2020); https://doi.org/10.3390/cryst10090804.
[6] E. Singh et al., Phys. Rev. B 106, 144103 (2022); https://doi.org/10.1103/PhysRevB.106.144103.
[7] L.L. Ding et al., Appl. Phys. Lett. 124, 252901 (2024); https://doi.org/10.1063/5.0205877.
[8] L.M. Eng et al., Appl. Phys. Lett. 74, 233 (1999); https://doi.org/10.1063/1.123266.
[9] U. Acevedo-Salas et al., Nano Lett. 23, 795 (2023); https://doi.org/10.1021/acs.nanolett.2c03579.