Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 86: Electronic Structure of Surfaces: Spectroscopy, Surface States II

O 86.1: Vortrag

Donnerstag, 20. März 2025, 15:00–15:15, H2

Low temperature STM/AFM detection of 2D electronic gas on reduced SrTiO₃ surface — •Akash Gupta, Marcin Kisiel, Remy Pawlak, and Ernst meyer — Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland

Perovskite such as SrTiO₃ ubiquitous to host various reconstruction with fine tuning of the annealing temperature. At 1050^∘C, in oxygen poor conditions, a √5×√5 surface reconstruction is formed with oxygen vacancies. These oxygen vacancies result in compactly confined electrons as two-dimensional electron gas (2DEG) system. The 2DEG is confirmed as filled surface states in Low Temperature (4 K, UHV) Scanning Tunneling Spectroscopy (STS). Additionally, Image Potential States (IPS) emerges at lower energies than vacuum level, revealing work function, as well. The charging of this 2DEG system can be induced with capacitively coupled tip of Atomic Force Microscope, and it results in giant dissipation peaks as signature of surface charging with change in the tip-sample voltage. Furthermore, quantum capacitance is calculated as function of the gate voltage. The evolution of dissipation peaks were observed with tip-sample distance. The Force-Distance curves confirm the 2DEG charging and is used to determine the tunneling rate of the charging within 2DEG system.

Keywords: Oxide Surfaces; two-dimensional electron gas (2DEG); Scanning Tunneling Spectroscopy; Image Potential States; Dissipation