Defect structure of TiS3 single crystals with different resistivity

A defect structure of single-crystal whiskers TiS 3 with different resistivity has been studied by the high resolution scanning transmission electron microscopy. The whiskers crystallize in one monoclinic lattice, but in two variants, A and B. The high-resistivity whiskers crystallize according to the A-variant, while the crystal structure of the low-resistivity whiskers is a mixture of the A- and B-variants. All planar defects in the crystals are described in terms of twinning with the twin boundaries running parallel to the (001) plane and located in the middle of the atomic layers. Sulfur vacancies are found both in high- and low-resistivity whiskers, but the density of vacancies is noticeably higher in the low-resistivity ones. It is shown that the magnitude and temperature dependence of the resistivity are determined by the density of vacancies and the number of B-domains in the TiS 3 crystals, whereas the effect of twinning on the resistivity is negligible.