TRAP STATE DYNAMICS IN MOS2 NANOCLUSTERS

The trap-to-trap relaxation and recombination dynamics of photogenerat ed electron/hole pairs in MoS2 nanoclusters have been studied. Static and time-resolved emission experiments have been performed on 3.0 and 4.5 nm diameter nanoclusters in ternary inverse micelles, acetonitrile , and octane at room temperature and at 20 K. The results indicate tha t, following synthesis in ternary inverse micelles, the nanoclusters h ave both shallow and deep traps. The deep traps are retained upon extr action into acetonitrile and passivated upon charge neutralization and reextraction into octane. The emission kinetics show that trap-to-tra p relaxation is fast (<40 ps) at room temperature and slows (similar t o 200 ps) at 20 K. A distributed kinetics model is presented that quan titatively describes electron/hole recombination. The trapped electron Bohr radius is found to be 2.0-2.5 nm in all cases. Charge neutraliza tion and reextraction into octane passivates both the deep and the sha llow traps on some nanoclusters, resulting in indirect band edge emiss ion at 20 K.