OPTICALLY DETECTED MAGNETIC-RESONANCE STUDY OF ELECTRON HOLE TRAPS ONCDSE QUANTUM-DOT SURFACES/

Thin films of CdSe nanoparticles were chemically deposited on a glass substrate. The PL spectra of these films are dominated by a red-IR emi ssion band, associated with the recombination of shallow trapped elect rons and deep trapped holes. The optically detected magnetic resonance (ODMR) measurements revealed that the trapping sites have low symmetr y, thus suggesting their existence at the surface of the nanoparticles . Moreover, the theoretical simulation suggests a distribution of e-h pair distances, leading to an ensemble of exchange interaction values. The trapping sites are distributed around the circumference of the na noparticles, and the e-h spatial separation is therefore limited by th e size of the nanoparticles. The g values of the trapped carriers are substantially different from those of the band edge, further supportin g the idea of trapped carrier localization at imperfection sites.