Temperature variation of photoconductivity in the layered quasi one-dimensional compound TiS3: Semiconducting and unconventional behavior

The layered quasi one-dimensional compound TiS3 is remarkable for its optical properties, especially, photoconductivity. Up to now, photoconductivity in TiS3 was studied only at room temperature. Here, we report photoconductivity, delta sigma, of the TiS3 whiskers in the temperature range of 5-300 K under irradiation in the near-infrared region. With a temperature decrease from room temperature down to T similar to 100 K, delta sigma grows moderately, dominated by the variation of the mobility of the electrons. The estimates based on the values of delta sigma give the recombination time similar to 3-25 mu s at 300 K. The results show that above similar to 100 K, TiS3 behaves as a semiconductor, where electron-hole pairs are excited across the gap, while the recombination goes through transitions of the excited electrons to a donor level with a long lifetime. Below 60 K, a drop of delta sigma is likely to reveal a phase transition of electrons into a collective state. Another feature in delta sigma(T) is seen around 17 K, resembling the temperature variation of the conductivity. This feature indicates a drop in the mobility of the electrons. While the behavior of delta sigma(T) is consistent with the transition of electrons into a collective state, it is strikingly different from delta sigma(T) of the known quasi one-dimensional conductors with charge-density waves.& nbsp;& nbsp;Published under an exclusive license by AIP Publishing.

Automated summary

The layered quasi one-dimensional compound TiS3 exhibits remarkable optical properties, especially photoconductivity, which is influenced by the mobility of electrons. As the temperature decreases, the photoconductivity of TiS3 increases moderately, showing semiconductor behavior above approximately 100 K and a potential phase transition into a collective state below 60 K. Additionally, a drop in electron mobility is observed around 17 K.