TY  - JOUR
A1  - Gabel, Judith
A1  - Pickem, Matthias
A1  - Scheiderer, Philipp
A1  - Dudy, Lenart
A1  - Leikert, Berengar
A1  - Fuchs, Marius
A1  - Stübinger, Martin
A1  - Schmitt, Matthias
A1  - Küspert, Julia
A1  - Sangiovanni, Giorgio
A1  - Tomczak, Jan M.
A1  - Held, Karsten
A1  - Lee, Tien–Lin
A1  - Claessen, Ralph
A1  - Sing, Michael
T1  - Toward Functionalized Ultrathin Oxide Films: The Impact of Surface Apical Oxygen
JF  - Advanced Electronic Materials
N2  - Thin films of transition metal oxides open up a gateway to nanoscale electronic devices beyond silicon characterized by novel electronic functionalities. While such films are commonly prepared in an oxygen atmosphere, they are typically considered to be ideally terminated with the stoichiometric composition. Using the prototypical correlated metal SrVO\(_{3}\) as an example, it is demonstrated that this idealized description overlooks an essential ingredient: oxygen adsorbing at the surface apical sites. The oxygen adatoms, which are present even if the films are kept in an ultrahigh vacuum environment and not explicitly exposed to air, are shown to severely affect the intrinsic electronic structure of a transition metal oxide film. Their presence leads to the formation of an electronically dead surface layer but also alters the band filling and the electron correlations in the thin films. These findings highlight that it is important to take into account surface apical oxygen or—mutatis mutandis—the specific oxygen configuration imposed by a capping layer to predict the behavior of ultrathin films of transition metal oxides near the single unit-cell limit.
KW  - transition metal oxides
KW  - correlated oxides
KW  - electronic phase transitions
KW  - photoelectron spectroscopy
KW  - thin films
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318914
SN  - 2199-160X
VL  - 8
IS  - 4
ER  - 
TY  - JOUR
A1  - Müller, S.
A1  - Spriestersbach, F.
A1  - Min, C.-H.
A1  - Fornari, C. I.
A1  - Reinert, F.
T1  - Molecular beam epitaxy of TmTe thin films on SrF\(_{2}\) (111)
JF  - AIP Advances
N2  - The odd parity nature of 4f states characterized by strong spin–orbit coupling and electronic correlations has led to a search for novel topological phases among rare earth compounds, such as Kondo systems, heavy Fermions, and homogeneous mixed-valent materials. Our target system is thulium telluride thin films whose bandgap is expected to be tuned as a function of lattice parameter. We systematically investigate the growth conditions of TmxTey thin films on SrF\(_{2}\) (111) substrates by molecular beam epitaxy. The ratio between Te and Tm supply was precisely tuned, resulting in two different crystalline phases, which were confirmed by x-ray diffraction and x-ray photoemission spectroscopy. By investigating the crystalline quality as a function of the substrate temperature, the optimal growth conditions were identified for the desired Tm1Te1 phase. Additional low energy electron diffraction and reflective high energy electron diffraction measurements confirm the epitaxial growth of TmTe layers. X-ray reflectivity measurements demonstrate that homogeneous samples with sharp interfaces can be obtained for varied thicknesses. Our results provide a reliable guidance to prepare homogeneous high-quality TmTe thin films and thus serve as a basis for further electronic investigations.
KW  - thulium telluride
KW  - molecular beam epitaxy
KW  - thin films
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300876
VL  - 12
IS  - 2
ER  -