Defect Engineering in CdS_<i>x</i>Se_1–<i>x</i> Nanobelts: An Insight into Carrier Relaxation Dynamics via Optical Pump–Terahertz Probe Spectroscopy

Abstract

Defects in nanomaterials often induce dramatic changes in the photoelectrical properties of semiconducting II–VI compound nanomaterials. The relationship between defects and carrier dynamics is pivotal in material engineering for potential applications. A thorough understanding of the dynamics of defect-related free carrier depletion is particularly important for the fabrication and optimization of nano-optoelectronic devices. In this work, optical pump–terahertz probe spectroscopy was employed to investigate the carrier dynamics in CdS and Se-alloyed CdS nanobelts. The dynamics are dominated by the surface defect trapping in the case of CdS and structural-defect-related recombination for the Se-alloyed CdS. The conclusion is also supported by temperature-dependent photoluminescence spectroscopic studies. Our results indicate that congeneric element replacement is an effective approach for defect-distribution restructuring, which modifies the physical properties of nanomaterials through defect engineering.