Anomalous structural disorder and distortion in metal-to-insulator-transition Ti2O3

作者：Hwang, In-Hui; Jiang, Bingzhi; Jin, Zhenlan; Park, Chang-In; Han, Sang-Wook^*

来源：Journal of Applied Physics, 2016, 119(1): 014905.

DOI：10.1063/1.4939290

• X-RAY
• ORDER
• VO2
• SPECTROSCOPY
• OXIDES

Mott proposed that impurity bands in corundum-symmetry Ti2O3 at high temperatures caused a collapse in the bandgap. However, the origin of the impurity bands has not yet been clarified. We examine the local structural properties of metal-to-insulator-transition Ti2O3 using in-situ x-ray absorption fine structure (XAFS) measurements at the Ti K edge in the temperature range from 288 to 739 K. The Ti2O3 powder is synthesized by using a chemical reaction method. X-ray diffraction (XRD) measurements from Ti2O3 with a Rietveld refinement demonstrate a single-phased R-3c symmetry without additional distortion. Extended-XAFS combined with XRD reveals a zigzag patterned Ti position and an anomalous structural disorder in Ti-Ti pairs, accompanied by a bond length expansion of the Ti-Ti pairs along the c-axis for T > 450 K. The local structural distortion and disorder of the Ti atoms would induce impurity levels in the band gap between the Ti 3d a(1)g and e(g)(pi) bands, resulting in a collapse of the band gap for T > 450 K.

• 出版日期2016-1-7
• 单位延边大学