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

Journal Article · · Nano Letters
 [1];  [1];  [2];  [3];  [4];  [1];  [1];  [4];  [4];  [5];  [6];  [4];  [7]; ORCiD logo [1]; ORCiD logo [8]
  1. National Cheng Kung Univ., Tainan City (Taiwan)
  2. Lund Univ. (Sweden)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); National Synchrotron Radiation Research Center, Hsinchu (Taiwan)
  4. East China Normal Univ. (ECNU), Shanghai (China)
  5. Max Planck Institute for Chemical Physics of Solids, Dresden (Germany)
  6. National Chiao Tung Univ., Hsinchu (Taiwan); National Synchrotron Radiation Research Center, Hsinchu (Taiwan)
  7. Paul Scherrer Inst. (PSI), Villigen (Switzerland). Swiss Light Source; Lund Univ. (Sweden)
  8. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
+ Show Author Affiliations

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. Further, the spectroscopic measurements reveal the modified Ti-O orbital hybridization that causes the Ti ion to deviate from its nominal 4+ valency (3do 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.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division; Ministry of Science and Technology (MOST), Taiwan; National Key Research and Development Program of China; National Natural Science Foundation of China (NSFC)
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1961810
Journal Information:
Nano Letters, Journal Name: Nano Letters Journal Issue: 4 Vol. 22; ISSN 1530-6984
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
RIXS
delocalized Ti 3d electrons
ferroelectricity
freestanding SrTiO3