Transport and optical properties ofTi1+xS2

Abstract

We report measurements of the dectrical resistivity, Hall coefficient, magnetoresistance, thermoelectric power, infrared reflectivity, and c-axis lattice parameter of single crystals of titanium disulfide Ti&+"S& with varying degrees of nonstoichiometry. The strong correlations we find between different measurements made on the same sample allow us to conclude that titanium disulfide is a semiconductor rather than a semimetal. Even though this fact is established, our most stoichiometric samples continue to exhibit metallic behavior, and the source of these conduction electrons is unknown. In addition, none of the scattering mechanisms examined here is capable of explaining the unusual temperature dependence of the electrical resistivity which varies as T' at low T and as T~a bove 100 K where y ranges from 1.85 for the least stoichiometric samples to 2.2 for the most stoichiometric.

Thermoelectric Properties of Co-Doped TiS2

“…Similarly, band calculations based on the augmented spherical wave (ASW) method by Fang et al, 9 the linear muffin-tin orbital (LMTO) method by Wu et al, [10][11][12] and the full-potential (FP)-LAPW method 13,14 showed that TiS 2 possessed a semimetallic ground state. Meanwhile, many experiments 15,16 have indicated that the electrical resistivity of TiS 2 almost exclusively exhibits metallic behavior, decreasing with decreasing temperature down to nearly 0 K. To date, no semiconductor behavior in the conductivity of TiS 2 has ever been observed experimentally. Hence, it is interesting and also significant (as mentioned below) to clarify the observed contradictory phenomena concerning the properties of TiS 2 .…”

“…To date, for instance, whether it is a semiconductor or semimetal has not been clarified. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Through measurements of the Hall coefficient, Seebeck coefficient, and resistivity as a function of pressure, Klipstein and Friend 2 found that the band overlap between S 3p states and Ti 3d states increased at a rate of 4.5 meV/kbar, and concluded that TiS 2 is a semiconductor with a gap of 0.18 ± 0.06 eV. The optical measurements of Greenway and Nische 3 indicated that TiS 2 is a semiconductor with a gap of 1 eV to 2 eV.…”

Large thermoelectric power factor inTiS2crystal with nearly stoichiometric composition

“…Transport properties of TiS 2 2 are strongly affected by its large off-stoichiometry. [11][12][13][14][15] were measured by the van der Pauw and Montgomery methods, respectively, using a lock-in technique in the temperature range from 4 to 300 K. Thermopower in this temperature range was measured by the conventional constant-∆T method. In-plane Hall resistivity up to 2 T was measured in the van der Pauw configuration by applying the magnetic field normal to the c-plane in the temperature range from 5 to 300 K. In-plane and out-of-plane thermal conductivities at room temperature were measured by the AC thermal diffusivity and the laser flush methods, respectively.…”

Density Functional Theory Evaluated for Structural and Electronic Properties of 1T-Li x TiS2 and Lithium Ion Migration in 1T-Li0.94TiS2

“…The band gap of TiS 2 was investigated many times both experimentally [57][58][59][60][61][62][63][64][65] and theoretically [5,11,[66][67][68][69][70][71][72][73][74]. Experimental studies suggest that TiS 2 is a semiconductor with a small indirect band gap between 0.18 eV [63] and 0.56 eV [65].…”