TY - JOUR
T1 - Evidence of a 2D Electron Gas in a Single-Unit-Cell of Anatase TiO2 (001)
AU - Troglia, Alessandro
AU - Bigi, Chiara
AU - Vobornik, Ivana
AU - Fujii, Jun
AU - Knez, Daniel
AU - Ciancio, Regina
AU - Dražić, Goran
AU - Fuchs, Marius
AU - Sante, Domenico Di
AU - Sangiovanni, Giorgio
AU - Rossi, Giorgio
AU - Orgiani, Pasquale
AU - Panaccione, Giancarlo
N1 - Publisher Copyright:
© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.
PY - 2022/6/3
Y1 - 2022/6/3
N2 - The formation and the evolution of electronic metallic states localized at the surface, commonly termed 2D electron gas (2DEG), represents a peculiar phenomenon occurring at the surface and interface of many transition metal oxides (TMO). Among TMO, titanium dioxide (TiO2), particularly in its anatase polymorph, stands as a prototypical system for the development of novel applications related to renewable energy, devices and sensors, where understanding the carrier dynamics is of utmost importance. In this study, angle-resolved photo-electron spectroscopy (ARPES) and X-ray absorption spectroscopy (XAS) are used, supported by density functional theory (DFT), to follow the formation and the evolution of the 2DEG in TiO2 thin films. Unlike other TMO systems, it is revealed that, once the anatase fingerprint is present, the 2DEG in TiO2 is robust and stable down to a single-unit-cell, and that the electron filling of the 2DEG increases with thickness and eventually saturates. These results prove that no critical thickness triggers the occurrence of the 2DEG in anatase TiO2 and give insight in formation mechanism of electronic states at the surface of TMO.
AB - The formation and the evolution of electronic metallic states localized at the surface, commonly termed 2D electron gas (2DEG), represents a peculiar phenomenon occurring at the surface and interface of many transition metal oxides (TMO). Among TMO, titanium dioxide (TiO2), particularly in its anatase polymorph, stands as a prototypical system for the development of novel applications related to renewable energy, devices and sensors, where understanding the carrier dynamics is of utmost importance. In this study, angle-resolved photo-electron spectroscopy (ARPES) and X-ray absorption spectroscopy (XAS) are used, supported by density functional theory (DFT), to follow the formation and the evolution of the 2DEG in TiO2 thin films. Unlike other TMO systems, it is revealed that, once the anatase fingerprint is present, the 2DEG in TiO2 is robust and stable down to a single-unit-cell, and that the electron filling of the 2DEG increases with thickness and eventually saturates. These results prove that no critical thickness triggers the occurrence of the 2DEG in anatase TiO2 and give insight in formation mechanism of electronic states at the surface of TMO.
KW - 2D electron gas
KW - anatase
KW - angle-resolved photo-electron spectroscopy
KW - ultra-thin oxides
UR - http://www.scopus.com/inward/record.url?scp=85127577998&partnerID=8YFLogxK
U2 - 10.1002/advs.202105114
DO - 10.1002/advs.202105114
M3 - Article
C2 - 35384406
AN - SCOPUS:85127577998
SN - 2198-3844
VL - 9
JO - Advanced Science
JF - Advanced Science
IS - 16
M1 - 2105114
ER -