TY - JOUR
T1 - Tunable Se vacancy defects and the unconventional charge density wave in 1T-TiSe2-δ
AU - Huang, S. H.
AU - Shu, G. J.
AU - Pai, Woei Wu
AU - Liu, H. L.
AU - Chou, F. C.
PY - 2017/1/31
Y1 - 2017/1/31
N2 - A systematic study of polycrystalline 1T-TiSe2-δ with controlled Se loss indicates that the unconventional charge density wave (CDW) phase is found to be most pronounced in samples with δ∼0.12, instead of being Se vacancy free. The level of Se vacancy defects and temperature determines whether 1T-TiSe2-δ should be categorized as a semiconductor, a semimetal, or an excitonic insulator. An interpretation using a general band picture of p-type doped narrow-band-gap semiconductor with an impurity band (IB) in proximity to the valence band (VB) is proposed to explain the evolution of electronic structures for 1T-TiSe2-δ, from the intermediate doping of δ∼0.08, to the critical doping of δ∼0.12 showing an anomalous resistivity peak between ∼100-200K, and to the heavily doped of δ∼0.17 as an n-type degenerate semiconductor. Integrated chemical analysis and physical property characterization, including electron probe microanalysis (EPMA), synchrotron x-ray diffraction, resistivity, and Seebeck coefficient measurement results are provided for the polycrystalline samples prepared via vacuum-sealed high temperature annealing route.
AB - A systematic study of polycrystalline 1T-TiSe2-δ with controlled Se loss indicates that the unconventional charge density wave (CDW) phase is found to be most pronounced in samples with δ∼0.12, instead of being Se vacancy free. The level of Se vacancy defects and temperature determines whether 1T-TiSe2-δ should be categorized as a semiconductor, a semimetal, or an excitonic insulator. An interpretation using a general band picture of p-type doped narrow-band-gap semiconductor with an impurity band (IB) in proximity to the valence band (VB) is proposed to explain the evolution of electronic structures for 1T-TiSe2-δ, from the intermediate doping of δ∼0.08, to the critical doping of δ∼0.12 showing an anomalous resistivity peak between ∼100-200K, and to the heavily doped of δ∼0.17 as an n-type degenerate semiconductor. Integrated chemical analysis and physical property characterization, including electron probe microanalysis (EPMA), synchrotron x-ray diffraction, resistivity, and Seebeck coefficient measurement results are provided for the polycrystalline samples prepared via vacuum-sealed high temperature annealing route.
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U2 - 10.1103/PhysRevB.95.045310
DO - 10.1103/PhysRevB.95.045310
M3 - Article
AN - SCOPUS:85012293299
VL - 95
JO - Physical Review B
JF - Physical Review B
SN - 2469-9950
IS - 4
M1 - 045310
ER -