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

Chiu, Chun Chien ; Ho, Sheng Zhu ; Lee, Jenn Min LU ; Shao, Yu Cheng ; Shen, Yang ; Liu, Yu Chen ; Chang, Yao Wen ; Zheng, Yun Zhe ; Huang, Rong and Chang, Chun Fu , et al. (2022) In Nano Letters 22(4). p.1580-1586
Abstract

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... (More)

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.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
delocalized Ti 3d electrons, ferroelectricity, freestanding SrTiO, RIXS
in
Nano Letters
volume
22
issue
4
pages
7 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • pmid:35073104
  • scopus:85124169415
ISSN
1530-6984
DOI
10.1021/acs.nanolett.1c04434
language
English
LU publication?
yes
id
f05ea6af-2ef0-4f9f-860f-d3d50e0ae81e
date added to LUP
2022-05-16 15:51:52
date last changed
2025-04-04 15:20:08
@article{f05ea6af-2ef0-4f9f-860f-d3d50e0ae81e,
  abstract     = {{<p>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 SrRuO<sub>3</sub> 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 (3d<sup>0</sup> configuration) with excess delocalized 3d electrons. Additionally, the Ti ion in TiO<sub>6</sub> 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.</p>}},
  author       = {{Chiu, Chun Chien and Ho, Sheng Zhu and Lee, Jenn Min and Shao, Yu Cheng and Shen, Yang and Liu, Yu Chen and Chang, Yao Wen and Zheng, Yun Zhe and Huang, Rong and Chang, Chun Fu and Kuo, Chang Yang and Duan, Chun Gang and Huang, Shih Wen and Yang, Jan Chi and Chuang, Yi De}},
  issn         = {{1530-6984}},
  keywords     = {{delocalized Ti 3d electrons; ferroelectricity; freestanding SrTiO; RIXS}},
  language     = {{eng}},
  month        = {{02}},
  number       = {{4}},
  pages        = {{1580--1586}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Nano Letters}},
  title        = {{Presence of Delocalized Ti 3d Electrons in Ultrathin Single-Crystal SrTiO<sub>3</sub>}},
  url          = {{http://dx.doi.org/10.1021/acs.nanolett.1c04434}},
  doi          = {{10.1021/acs.nanolett.1c04434}},
  volume       = {{22}},
  year         = {{2022}},
}