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

• DOI: 10.1021/acs.nanolett.1c04434
• Publication Date: 2022-01-24T17:25:40Z
• Authors: Chun-Chien Chiu; Sheng-Zhu Ho; Jenn-Min Lee; Yu-Cheng Shao; Yang Shen; Yu-Chen Liu; Yao-Wen Chang; Yun-Zhe Zheng; Rong Huang; Chun-Fu Chang; Chang-Yang Kuo; Chun-Gang Duan; Shih-Wen Huang; Jan-Chi Yang; Yi-De Chuang
• Keywords: Tetragonal crystal system; Valency; Strontium titanate

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