Investigation of Single Semiconductor Nanowire Heterostructures Using Polarized Imaging Spectroscopy
Year: 2008
Type: article
Abstract: In this work, we use optical spectroscopic techniques including microphotoluminescence (PL), spatially-resolved PL imaging, time-resolved PL, PL polarization measurements to investigate the optical and electronic properties of single CdS and core-shell GaAs/AlGaAs nanowires (NWs) at both room and low temperatures.CdS nanowires grown by the Vapor-Liquid-Solid (VLS) method show variation in morphology ranging from straight and uniform, to extremely irregular with bends, kinks, and irregular shaped clusters of material aggregating locally on the nanowires.At room temperature we observe that all nanowires, regardless of size and shape, emit PL with a single broad peak with Full Width at Half Maximum (FWHM) ~ 70 meV at energy below the band gap energy of bulk CdS (2.51 eV).The emission is often referred as the Near Band Edge (NBE) emission.At low temperature, PL emission from these nanowires are significantly different: PL from uniform wires still display a broad peak near 2.54 eV (FWHM ~32 meV) but irregular wires show a broad band with a high energy shoulder near ~2.54 eV and a number of sharp emission lines are observed on the lower energy side of the broad band.Spatially resolved PL imaging and temperature dependent PL measurements reveal that these sharp emission lines originate from specific positions along the nanowire and are completely quenched by 80-90K.Time-resolved measurements show that the decay times of the emission from the high energy shoulder (or near band edge) is very short (< 50 ps) while it is significantly longer for the sharp lines (500-1000 ps).We conclude that the sharp emission lines result from defect or surface related electron states.iii v First of all, I would like to express my special gratitude to my research advisor, Dr. Leigh Smith, for his ideas, instruction
Author: Thang B. Hoang
Institution: University of Cincinnati
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2600571075