title: Dynamics of bound exciton complexes in CdS nanobelts.
abstract: Intrinsic defects such as vacancies, interstitials, and anti-sites often introduce rich luminescent properties in II-VI semiconductor nanomaterials. A clear understanding of the dynamics of the defect-related excitons is particularly important for the design and optimization of nanoscale optoelectronic devices. In this paper, low-temperature steady-state and time-resolved photoluminescence (PL) spectroscopies have been carried out to investigate the emission of cadmium sulfide (CdS) nanobelts that originates from the radiative recombination of excitons bound to neutral donors (I(2)) and the spatially localized donor-acceptor pairs (DAP), in which the assignment is supported by first principle calculations. Our results verify that the shallow donors in CdS are contributed by sulfur vacancies while the acceptors are contributed by cadmium vacancies. At high excitation intensities, the DAP emission saturates and the PL is dominated by I(2) emission. Beyond a threshold power of approximately 5 μW, amplified spontaneous emission (ASE) of I(2) occurs. Further analysis shows that these intrinsic defects created long-lived (spin triplet) DAP trap states due to spin-polarized Cd vacancies which become saturated at intense carrier excitations.
authors: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.
authors: Xinlong
authors: X
authors: Xu
authors: Yanyuan
authors: Y
authors: Zhao
authors: Edbert Jarvis
authors: EJ
authors: Sie
authors: Yunhao
authors: Y
authors: Lu
authors: Bo
authors: B
authors: Liu
authors: Sandy Adhitia
authors: SA
authors: Ekahana
authors: Xiao
authors: X
authors: Ju
authors: Qike
authors: Q
authors: Jiang
authors: Jianbo
authors: J
authors: Wang
authors: Handong
authors: H
authors: Sun
authors: Tze Chien
authors: TC
authors: Sum
authors: Cheng Hon Alfred
authors: CH
authors: Huan
authors: Yuan Ping
authors: YP
authors: Feng
authors: Qihua
authors: Q
authors: Xiong
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D004579:Electron Transport; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D018036:Selenium Compounds / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; C058667:cadmium selenide