scholarly journals Unusual Blueshifting of Optical Band Gap of CdS Nanocrystals through a Chemical Bath Deposition Method

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Shu Qing Yuan ◽  
Peng Fei Ji ◽  
Yong Li ◽  
Yue Li Song ◽  
Feng Qun Zhou
Keyword(s):  
Band Gap ◽  
Chemical Bath Deposition ◽  
Optical Band Gap ◽  
Quantum Effect ◽  
Wide Band ◽  
Chemical Bath Deposition Method ◽  
Band Gaps ◽  
Deposition Method ◽  
Defect States ◽  
Cds Nanocrystals

CdS nanocrystals are synthesized through a chemical bath deposition method. After annealing, these nanocrystals are enlarged according to Scherrer’s formula. Small nanocrystals display wide band gaps as a result of the quantum effect experienced by nanocrystals of a certain size. However, the absorption edge and green and red emissions of annealed CdS nanocrystals show obvious blueshift compared with the as-grown ones. After annealing, the intensity ratio of these green and red emissions increases, which indicated that the defect states are reduced. Therefore, the improvement in crystalline quality and the reduced strain contribute to the unusual blueshifting of the optical band gap and of the green and red emissions.

PERFECT OPTICAL TRANSPORT AND OPTICAL BAND GAP IN QUASIPERIODIC SUPERLATTICES

2012 ◽  
Vol 26 (17) ◽  
pp. 1250110
Author(s):  
XIA YU ◽  
KE-QIU CHEN ◽  
YAN ZHANG
Keyword(s):  
Refractive Index ◽  
Band Gap ◽  
Optical Band Gap ◽  
Negative Refractive Index ◽  
Low Frequency ◽  
Wide Band ◽  
Band Gaps ◽  
Transmission Coefficients ◽  
Refractive Index Material ◽  
Superlattice Structures

A three-component quasiperiodic superlattice structures composing of both positive and negative refractive index materials are shown to display resonant transport behavior and optical band gaps. When the structure is composed of nondispersive refractive index material, the number of the resonant transmission peaks increases and the optical band gap becomes broad with the increasing of the medium generation. The band gap covers all the wavelength except for some singular wavelength points when the structure is composed of negative refractive index materials. Moreover, it is found that the spectrum shifts to low frequency for oblique incidence. And with the increasing of the optical thickness, the band gap splits and new perfect transport channels emerge. For a more realistic dispersive negative refractive index material, the transmission coefficients are characterized by a rich transmission profile without symmetry, more wide band gaps and abundance transmissive channels appear.

scholarly journals Synthesis and characterization of PbS nanowires doped with Tb3+ ions by using chemical bath deposition method

2019 ◽  
Vol 10 (1) ◽  
pp. 1-7 ◽  
Author(s):  
L. F. Koao ◽  
Fekadu Gashaw Hone ◽  
F. B. Dejene
Keyword(s):  
Band Gap ◽  
Chemical Bath Deposition ◽  
Potassium Hydroxide ◽  
Luminescent Properties ◽  
Deposition Process ◽  
Chemical Bath Deposition Method ◽  
Deposition Method ◽  
X Ray Diffraction ◽  
X Ray

AbstractCrystalline lead sulfide (PbS) nanowires doped with terbium (Tb3+) ions were synthesized by the chemical bath deposition method at room temperature. The powder was obtained from an aqueous solutions using lead acetate dehydrate, terbium nitrate, thiourea, potassium hydroxide and ammonia. The terbium molar concentrations were varied in the deposition process to investigate the effect on the structural, optical, morphological and luminescent properties of PbS nanowires. The crystalline size was found to be dependent on the concentration of the Tb3+ ions used. The estimated average crystalline sizes were calculated from the X-ray diffraction and found to be 34, 33 and 37 nm for PbS: 0% Tb3+, PbS: 0.2% Tb3+ and PbS: 0.5% Tb3+, respectively. The scanning electron microscopy micrographs depict nanowire shape for the undoped as well as Tb-doped samples. The energy-dispersive X-ray and Auger electron spectroscopy analyses confirmed the presence of all the expected elements. The solid powder nanowires exhibited high absorptions in the UV–Vis regions. The band gap energies were estimated in the range of 1.99–2.46 eV. The absorption edge and the band gap energies of these PbS nanowires have shifted depending on the concentration of the dopant. The maximum luminescence intensity was obtained for PbS: 0.2% Tb3+ ions and luminescent quenching was observed for higher terbium concentrations. Graphic abstract

Synthesis, Structural and Optical Characterization of PVA Capped Cadmium Sulphide Nanocrystalline Films by Chemical Bath Deposition Method

2013 ◽  
Vol 665 ◽  
pp. 341-346
Author(s):  
L. Sujata Devi ◽  
K. Nomita Devi ◽  
B. Indrajit Sharma ◽  
H. Nandakumar Sarma
Keyword(s):  
Band Gap ◽  
Crystallite Size ◽  
Chemical Bath Deposition ◽  
Cadmium Sulphide ◽  
Average Crystallite Size ◽  
Optical Characterization ◽  
Chemical Bath Deposition Method ◽  
Approximation Formula ◽  
Deposition Method ◽  
Nanocrystalline Films

Nanocrystalline CdS thin films were deposited on glass substrate by chemical bath deposition method using Cadmium Sulphate and Thiourea as Cd+2and S-2ion sources for different molarities i.e. 0.1 M, 0.2 M and 0.3 M. The crystallite size and lattice parameters for each sample were determined from X-Ray diffraction data using Scherrers formula. The value of the crystallite size was found to be within the range 14.7 nm-11.4 nm. The optical characterization was done by UV-Visible and photoluminescence spectroscopy. The optical band gap of the films was determined from the transmittance spectra. It was observed that when the molarity increases, the average crystallite size decreases and the band gap energy of the prepared films increases. Photoluminescence studies showed a prominent peak at around 530 nm. The radius of the nanocrystalline films had been evaluated from the absorption spectrum by using effective mass approximation formula.

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