Se vacancy defect and charge density wave in 1T-TiSe2
S. H. Huang1,2*, G. J. Shu2, Woei Wu Pai2, H. L. Liu1, F. C. Chou2
1Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan
2Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
* presenting author:黃松勳,
1T-TiSe2 has been categorized as either a semiconductor or semimetal in many early studies, which has shown great sample-dependent results for materials prepared at different temperatures. The defect nature of this Ti-Se binary has been assumed to be Ti1+XSe2 or TiSe2-δ with controversy. We have prepared a series of 1T-TiSe2 single crystal and polycrystalline samples and annealed in vacuum from 350-950 °C to create defects at different levels. With the combined x-ray powder diffraction, electron probe microanalysis, resistivity, susceptibility, and scanning tunneling microscopic studies, we confirmed that the defect is Se vacancy type. Furthermore, the character of the charge density wave phase transition is affected by the Se deficiency level significantly. Additionally, surface scanning tunneling microscopic images of 1T-TiSe2-δ obtained from various annealing temperatures are compared and modeled as a proof for the existence of Se vacancy defect.

Keywords: TiSe2, CDW (charge density wave)