Ultrafast exciton dynamics in ZnxCd1-xSe nanobelt.

• Main Author: Sulistio, Arief.
• Other Authors: Sum Tze Chien
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Science::Physics::Optics and light
• Online Access: http://hdl.handle.net/10356/54674
• Institution: Nanyang Technological University

ZnxCd1-xSe nanobelts are interesting ternary alloy nanostructures with many unique properties suitable for lasing applications. Herein, we investigate the potential use of ZnxCd1-xSe nanobelt as a room-temperature gain medium for single photon and two photon pump lasing. Ultrafast femtosecond laser was used to probe the exciton dynamics in this material. The emission spectra shows a continuous shift of band edge emission from 460nm to 730nm which correspond to pure ZnSe and CdSe emission, indicating a formation of ternary alloy rather than mixed of independent binary phases. We also examined the pump power dependence of emission which exhibits a super linear relationship above certain pump threshold. This threshold increasing with high concentration of Cd in composition and jumps significantly around 650nm. The time resolved emission shows two different decay time which correspond to surface and intrinsic transitions. We find that the intrinsic transition become longer as approaching CdSe side. This result is consistent with previous observation, as fast decay will lead to faster recombination while slower decay time lead to more excitons trapped in defect state. To understand this superlinear increment of emission, we explore the origin of this emission by obtaining absorption spectrum and power dependent emission from single nanobelt using micro PL setup. Above the pump threshold, we observe multiple peaks emitted from a single nanobelt with constant spacing depend on its length, indicating that the different lasing modes corresponding to a Fabry Perot cavity present in the nanobelt.