Book/Dissertation / PhD Thesis

FZJ-2020-00295

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Chemical control of the electrical surface properties of n-doped transition metal oxides

Andrä, M. T. (Corresponding author)FZJ*

2019
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-448-5

Please use a persistent id in citations: http://hdl.handle.net/2128/23988

Abstract: Novel classes of materials are required to meet the technological challenges in modern electronics. By ultimately merging surface physics and band engineering approaches with the chemistry of complex oxides, oxide electronics are believed to meet the rapidly growing demands stemming from the decreasing structure size of electronic applications. A lot is known about the behavior of complex oxides in the bulk. Surfaces and interfaces, however, may show fundamentally varying properties due to the reduced dimension and short diffusion lengths involved. Thus, the surfaces of complex oxide semiconductors and especially their interfaces formed with other complex oxides and metals are expected to play an even more important role in the technological progress of the upcoming decades. In order to pave the way to novel tailored applications, understanding the redox processes at the complex oxide surfaces is essential. Within this thesis, state-of-the-art spectroscopic tools are used that allow for in-situ surface investigations in varying atmospheres thereby demonstrating the differences between surface and bulk chemistry and determine how space charge formation couples the surface chemistry and the electronic properties. By the utilization of ambient pressure photoelectron spectroscopy the previous experimental limitations of an undefined surface state and contamination that occurred due to the $\textit{ex-situ}$ transport of samples. The spectroscopic results determined on $\textit{n}$-SrTiO$_{3}$ single crystals and thin films clearly demonstrate the $\textit{p}$O$_{2}$-dependent activation of the strontium sublattice at intermediate temperatures that is accompanied by a shift of the Fermi level from the conduction band edge into the band gap. This shift illustrates an electron depletion layer being present at the $\textit{n}$-SrTiO$_{3}$ surface and thus the formation of a surface space charge layer. These findings are substantiated by electrical characterization of the surface contact and the $\textit{in-plane}$ sheet properties in Pt/$\textit{n}$-SrTiO$_{3}$ heterostructures and $\textit{n}$-SrTiO$_{3}$ thin films, respectively. The surface contact of the heterojunction exhibit an increased transport barrier after annealing in oxidizing conditions while the thin films demonstrate a reduced carrier concentration directly after growth in oxidizing conditions and a $\textit{p}$O$_{2}$-dependent in-plane sheet resistance.

Note: RWTH Aachen, Diss., 2019

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Contributing Institute(s):

1. Elektronische Materialien (PGI-7)

Research Program(s):

1. 524 - Controlling Collective States (POF3-524) (POF3-524)

Appears in the scientific report 2019

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