O-Doping Profile along ZnTe Nanowires Obtained Using Power-Dependent Microphotoluminescence Measurements

Abstract

We investigated the O-doping profile along ZnTe nanowires using laser powerdependent microphotoluminescence measurements. ZnTe nanowires were grown by physical vapor transport catalyzed by bismuth. The photoluminescence spectra consisted of band-edge green photoluminescence and red photoluminescence due to a highly luminescent intermediate band formed by unintentional O doping. An obvious color-tuning effect of photoluminescence was observed along the nanowire and was suggestive of the competition between two luminescence bands. A significant variation in the intensity of red luminescence from the catalyst tip to the bottom was observed, and the photoluminescence intensity as a function of excitation power at each sampling spot along the nanowire was analyzed using a power law. The exponent value in the power law, from the sampling spots, was determined to be 0.58 ± 0.11, indicating an identical recombination channel for red luminescence. However, the O-doping density shows a superlinear increase from the catalyst tip to the bottom. Besides the direct impingement of doping species on the side wall, the additional incorporation of the doping species surfacemigrating from the substrate may explain the nonlinear O-doping profile along the nanowire.

Tailored Emission Properties of ZnTe/ZnTe:O/ZnO Core–Shell Nanowires Coupled with an Al Plasmonic Bowtie Antenna Array

“…To further probe the plasmonic coupling efficiency of a bowtie antenna with the nanowire, the power-dependent photoluminescence characteristics under transverse-polarized light excitation are shown in Figure (a). Besides the NBE emission at 2.26 eV (550 nm), a broad red emission of 1.72 eV (720 nm) is observed, which is ascribed to the radiative recombination from oxygen-induced intermediate band (IB) states to the valence band (VB) . A schematic of the optical transitions is shown in the band diagram (Figure (c)).…”

“…Besides the NBE emission at 2.26 eV (550 nm), a broad red emission of 1.72 eV (720 nm) are observed, which is ascribed to the radiative recombination from oxygen induced intermediate band (IB) states to VB. 17 A schematic of the optical transitions are shown in the band diagram (Fig. 1 (c)).…”

“…At high excitation condition, the intensity of IB emission is saturated and dropped due to the limited density of states of the intermediate band, while NBE emissions increase continuously in intensity. 17 In comparison, both NBE and IB emissions of the nanowire/antenna structure are enhanced, which has been normally regarded as the surface enhanced fluorescence (SEF). 29 However, the enhancement magnitude from nanowire/antenna structure exhibits a strong dependence on excitation power.…”

“…[17][18][19] The excitonic emission bound to the intermediate band states is also still below the demand 4 for the practical application due to its low density of states and low quantum efficiency. 17 To solve this problem, plasmonic coupling with metallic nanostructures is an alternative way for transferring energy and manipulating optical properties of low-efficient emitters. 20 "Bowtie" antennas, a sort of dimer nanoantennas with strong geometric resonances, have been proven to achieve high quantum efficiency while keeping nonradiative absorption weaker and large local field enhancement in the narrow gap between two coupled metallic nanostructures.…”

“…Strong exciton–phonon coupling in ZnTe nanobelts was demonstrated to significantly enhance the exciton radiative decay rates . However, as compared to other II–VI high-efficient emitting materials, the quantum yield of ZnTe nanostructures is lower with a recorded value up to 60%. − The excitonic emission bound to the intermediate band states is also still below the demand for practical applications due to its low density of states and low quantum efficiency . To solve this problem, plasmonic coupling with metallic nanostructures is an alternative way for transferring energy and manipulating optical properties of low-efficient emitters .…”