Mechanism for Size Dependence of Light Emission From ZnO Nanocrystallites

2007 ◽  
Author(s):  
Fuli Zhao ◽  
Xiaofang Wang ◽  
Pingbo Xie ◽  
Ningsheng Xu ◽  
Zhizhan Xu
Keyword(s):  
Band Gap ◽  
Zno Nanoparticles ◽  
Size Dependence ◽  
Laser Excitation ◽  
Light Emission ◽  
Surface States ◽  
Picosecond Laser ◽  
One Dimensional ◽  
1D Model ◽  
Critical Grain Size

Broadband light emission of different sized ZnO nanoparticles (17 nm to 300 nm) has been measured under picosecond laser excitation. Each spectrum consists of three Gaussian components including one emerging inside band-gap. Such inside band-gap band shows a clear dependence of the weighted intensity on the sizes of nanoparticles. Originated from our simplified one-dimensional (1D) model it has been qualitatively deduced that such size dependence match with the surface-state modified band structure. Additionally, a critical grain size as 110 nm for surface states recombination of ZnO nanoparticles has been found experimentally.

Surface states in one-dimensional photonic band gap structures

Vacuum ◽  
2001 ◽  
Vol 63 (1-2) ◽  
pp. 177-183 ◽  
Author(s):  
B Djafari-Rouhani ◽  
E.H El Boudouti ◽  
A Akjouj ◽  
L Dobrzynski ◽  
J.O Vasseur ◽  
...  
Keyword(s):  
Band Gap ◽  
Photonic Band Gap ◽  
Surface States ◽  
One Dimensional ◽  
Photonic Band Gap Structures ◽  
Photonic Band

Thermionic electron emission from narrow band-gap semiconductors under picosecond laser excitation

1998 ◽  
Vol 83 (8) ◽  
pp. 4462-4465 ◽  
Author(s):  
Samuel S. Mao ◽  
Xianglei Mao ◽  
Jong H. Yoo ◽  
Ralph Greif ◽  
Richard E. Russo
Keyword(s):  
Band Gap ◽  
Electron Emission ◽  
Laser Excitation ◽  
Narrow Band ◽  
Picosecond Laser ◽  
Thermionic Electron Emission ◽  
Narrow Band Gap Semiconductors

Surface States and Band Gap Correlation in Silicon Nanoclusters

2015 ◽  
Vol 1107 ◽  
pp. 308-313
Author(s):  
Sib Krishna Ghoshal ◽  
M.R. Sahar ◽  
R. Arifin ◽  
M.S. Rohani ◽  
K. Hamzah
Keyword(s):  
Band Gap ◽  
Surface Passivation ◽  
Light Emission ◽  
Radiative Lifetime ◽  
Surface States ◽  
Optical Gain ◽  
Visible Luminescence ◽  
Optical And Electronic Properties ◽  
Effect Of Oxygen

Tuning the visible emission of Si nanomaterials by modifying their size and shape is one of the key issue in optoelectronics. The observed optical gain in Si-nanoclusters (NCs) has given further impulse to nanosilicon research. We develop a phenomenological model by combining the effects of surface passivation, exciton states and quantum confinement (QC). The size and passivation dependent band gap, oscillator strength, radiative lifetime and photoluminescence (PL) intensity for NCs with diameter ranging from 1.0 to 6.0 nm are presented. By controlling a set of fitting parameters, it is possible to tune the optical band gap, PL peak and intensity. In case of pure clusters, the band gap is found to decrease with increasing NC size. Furthermore, the band gap increases on passivating the surface of the cluster with hydrogen and oxygen respectively in which the effect of oxygen is more robust. Both QC and surface passivation in addition to exciton effects determine the optical and electronic properties of silicon NCs. Visible luminescence is due to radiative recombination of electrons and holes in the quantum-confined NCs. The role of surface states on the band gap as well as on the HOMO-LUMO states is also examined and a correlation is established. Our results are in conformity with other observations. The model can be extended to study the light emission from other nanostructures and may contribute towards the development of Si based optoelectronics.

Excitonic Contribution of Nanosilicon on Light Emitting Properties

2011 ◽  
Vol 364 ◽  
pp. 308-312
Author(s):  
Sib Krishna Ghoshal ◽  
M.R. Sahar ◽  
M. Supar Rohani
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Size Dependence ◽  
Optical Band Gap ◽  
Surface States ◽  
Light Emitting ◽  
Optical And Electronic Properties ◽  
Pl Intensity ◽  
Excitonic Effects ◽  
Si Quantum Dots

A phenomenological model is developed by integrating the effect of excitonic energy states, localized surface states and quantum confinement (QC) to obtain an analytical expression for the room temperature photoluminescence (PL) intensity. We calculate the binding energy of strongly confined excitons in silicon (Si) quantum dots (QD) having sizes 1 to 7.75 nm to examine its contribution on optical band gap and electronic properties. The band gap with excitonic contribution is found to decrease as much as 0.23 eV for the smallest dot. The effect of exciton states explains almost accurately the experimental PL data. Our model provides the mechanism for controlling the PL intensity through fitting parameters. Huge excitonic effects, which depend strongly on QD size and shape, characterize the optical spectra. The results for the size dependence of the optical band gap, the PL intensity, and oscillator strength are presented the role excitonic effects on optical and electronic properties are discussed.

The Effect of Precursor Mixing Temperature during Precipitation Process on the Size of ZnO Nanoparticles and the Dispersion of ZnO@SiO2 Core-Shell Nanostructure

2014 ◽  
Vol 525 ◽  
pp. 108-116
Author(s):  
Akhmad Herman Yuwono ◽  
Nofrijon Sofyan ◽  
Vincentius Hamdani ◽  
Amalia Sholehah ◽  
Muhammad Arief
Keyword(s):  
Band Gap ◽  
Zno Nanoparticles ◽  
Light Emission ◽  
Surface Active Agent ◽  
Active Agent ◽  
Band Gap Energy ◽  
Cell Labeling ◽  
Precipitation Method ◽  
Precipitation Process ◽  
Gap Energy

ZnO nanoparticles have been used for many applications, including in cell labeling application. Its light emission can be used to determine and identify biology cells. Wet chemical precipitation method has been successfully done to synthesize the nanoparticle and it was subsequently continued by encapsulating with silica to keep ZnO stabilized in water to be properly used in cell labeling application. Varying precipitation temperatures has been performed to control the nanoparticle size and the addition of F127 surface active agent was carried out to prevent the agglomeration. The results showed the smallest nanoparticle (3.49 nm) was obtained from the process with temperature of 25oC, with the highest band gap energy, 3.12 eV. On the other hand, the largest nanoparticle (13.16 nm) was obtained from synthesis at temperature of 65oC, with the lowest band gap energy, 3.08 eV. These levels of band gap energy are potentially suitable for cell labeling application.

Lead chlorine cluster assembled one-dimensional halide with highly efficient broadband white-light emission

2021 ◽  
Author(s):  
Jian-Qiang Zhao ◽  
Chen Sun ◽  
Meng Yue ◽  
Yan Meng ◽  
Xian-Mei Zhao ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
White Light ◽  
Light Emission ◽  
White Light Emission ◽  
One Dimensional ◽  
Highly Efficient

One new lead chlorine cluster assembled 1D non-perovskite halide of [DTHPE]2Pb3Cl10 was synthesized which displays strong broadband bluish white light emission with a high photoluminescence quantum efficiency of 19.45% exceeding those of previously reported 2D lead perovskites.

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