Transient photoconductivity of ternary CDSSE nanobelts as measured by time-resolved terahertz spectroscopy

Abstract

The frequency-and fluence-dependent transient photoconductivity in ternary CdSSe nanobelts is investigated using time-resolved terahertz spectroscopy. The carrier density and mobility are extracted by modeling the measured complex photoconductivity using the Drude-Smith model. Within the first few picoseconds of excitation, both the carrier density and mobility reach their maximum values and then decay gradually over tens to hundreds of picoseconds. The decay of free carriers is mainly attributed to fast surface trapping and structural-defect- mediated recombination. The surface trapping saturates rapidly with increasing excitation fluence attributable to the low trapping density on the nanobelt surface caused by self-passivation of surface defects during the growth process. © 2013 American Chemical Society.