Presence of Delocalized Ti 3d Electrons in Ultrathin Single-Crystal SrTiO3

Strontium titanate (STO), with a wide spectrum of emergent properties such as ferroelectricity and superconductivity, has received significant attention in the community of strongly correlated materials. In the strain-free STO film grown on the SrRuO3 buffer layer, the existing polar nanoregions can facilitate room-temperature ferroelectricity when the STO film thickness approaches 10 nm. Here we show that around this thickness scale, the freestanding STO films without the influence of a substrate show the tetragonal structure at room temperature, contrasting with the cubic structure seen in bulk form. The spectroscopic measurements reveal the modified Ti-O orbital hybridization that causes the Ti ion to deviate from its nominal 4+ valency (3d0 configuration) with excess delocalized 3d electrons. Additionally, the Ti ion in TiO6 octahedron exhibits an off-center displacement. The inherent symmetry lowering in ultrathin freestanding films offers an alternative way to achieve tunable electronic structures that are of paramount importance for future technological applications.

Ho, Sheng ZhuNational Cheng Kung University (författare)
Lee, Jenn MinLund University,Lunds universitet,MAX IV-laboratoriet,MAX IV Laboratory(Swepub:lu)je6687le (författare)
Shao, Yu ChengNational Synchrotron Radiation Research Center Taiwan,Advanced Light Source, Berkeley (författare)
Shen, YangEast China Normal University (författare)
Liu, Yu ChenNational Cheng Kung University (författare)
Chang, Yao WenNational Cheng Kung University (författare)
Zheng, Yun ZheEast China Normal University (författare)
Huang, RongEast China Normal University (författare)
Chang, Chun FuMax Planck Institute for Chemical Physics of Solids (författare)
Kuo, Chang YangNational Chiao Tung University,National Synchrotron Radiation Research Center Taiwan (författare)
Duan, Chun GangEast China Normal University (författare)
Huang, Shih WenLund University,Lunds universitet,MAX IV-laboratoriet,MAX IV Laboratory,Paul Scherrer Institute(Swepub:lu)maxl-sha (författare)
Yang, Jan ChiNational Cheng Kung University (författare)
Chuang, Yi DeAdvanced Light Source, Berkeley (författare)
National Cheng Kung UniversityMAX IV-laboratoriet (creator_code:org_t)

Ingår i:Nano Letters: American Chemical Society (ACS)22:4, s. 1580-15861530-69841530-6992

Av författaren/redakt...: Chiu, Chun Chien; Ho, Sheng Zhu; Lee, Jenn Min; Shao, Yu Cheng; Shen, Yang; Liu, Yu Chen; visa fler...; Chang, Yao Wen; Zheng, Yun Zhe; Huang, Rong; Chang, Chun Fu; Kuo, Chang Yang; Duan, Chun Gang; Huang, Shih Wen; Yang, Jan Chi; Chuang, Yi De; visa färre...

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