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optical absorption in asymmetrical Gaussian potential quantum dot under the application of an electric field

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Chinese Physics B 2020年第8期29卷 437-440页

作者： Xue-Chao Li Chun-Bao Ye Juan Gao Bing Wang Optoelectronics Physics Anhui University of Science and TechnologyHuainan 232001China

We theoretically investigate the optical absorption coefficient(OAC)in asymmetrical Gaussian potential quantum dots subject to an applied electric *** wave functions together with energies of electron energies in an effective mass approximation framework are *** OAC is expressed according to the iterative method and the compact-density-matrix *** on our results,OAC is sensitively dependent on external electric field together with the incident optical ***,peak shifts into greater energy as the quantum dot radius ***,the parameters of Gaussian potential have a significant influence on the OAC.

关键词： electric field optical absorption quantum dot

Double band-inversions of bilayer phosphorene under strain and their effects on optical absorption

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Chinese Physics B 2018年第4期27卷 413-419页

作者： Shi He Mou Yang Rui-Qiang Wang Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials School of Physics and Telecommunication Engineering South China Normal University Guangzhou 510006 China

Strain is a powerful tool to engineer the band structure of bilayer *** band gap can be decreased by vertical tensile strain or in-plane compressive *** a critical strain,the gap is closed and the bilayer phosphorene is turn to be a semi-Dirac semimetal *** the strain is stronger than the criterion,a band-inversion occurs and it re-happens when the strain is larger than another certain *** the zigzag bilayer phosphorene ribbon,there are two edge band dispersions and each dispersion curve represents two degenerate edge *** the first band-inversion happens,one of the edge band dispersion disappears between the band-cross points while the other survives,and the latter will be eliminated between another pair of band-cross points of the second *** optical absorption of bilayer phosphorene is highly polarized along armchair *** the strain is turn on,the optical absorption edge *** absorption rate for armchair polarized light is decreased by gap shrinking,while that for zigzag polarized light *** bandtouch and band-inversion respectively result in the sublinear and linear of absorption curve versus light frequency in low frequency limit.

关键词： phosphorene electronic structure optical absorption strain

Effects of shape and dopant on structural, optical absorption,Raman, and vibrational properties of silver and copper quantum clusters: A density functional theory study

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Chinese Physics B 2014年第11期23卷 459-465页

作者：李维银陈福义 State Key Laboratory of Solidification Processing Northwestern Polytechnical University

We investigate the effects of shape and single-atom doping on the structural, optical absorption, Raman, and vibra- tional properties of Ag13, Ag12CUl, CUl3, and Cul2Agl clusters by using the （time-dependent） density functional the- ory. The results show that the most stable structures are cuboctahedron （COh） for Ag13 and icosahedron （Ih） for CUl3, Agl2CUlcore, and Cul2Aglsur. In the visible-near infrared optical absorption, the transitions consist of the interband and the intraband transitions. Moreover, red shifts are observed as follows： 1） clusters change from Agl2CUlcore to Ag13 to Ag12Culsur with the same motifs, 2） the shapes of pure Agl3 and Agl2CUlcore clusters change from COh to Ih to decahe- dron （Dh）, 3） the shape of Agl2CUlsur clusters changes from Ih to COh to Dh, and 4） the shapes of pure CU13 and Cu12Agl clusters change from Ih to Dh to COb. All of the Raman and vibrational spectra exhibit many significant vibrational modes related to the shapes and the compositions of the clusters. The ranges of vibrational spectra of Ag13, Agl2CUl or CU13, and Cu12Agl clusters become narrower and the vibrational intensities increase as the shape of the clusters changes from Ih to Dh to COh.

关键词： stability optical absorption Raman spectroscopy nanoclusters

Effect of Initialization Technical Parameters on optical absorption of Ge_2Sb_2Te_5 Thin Films

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Journal of Materials Science & Technology 2004年第5期20卷 509-511页

作者： Ming FANG, Qinghui LI and Fuxi GANShanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China Inst. of Optics and Fine Mech. Chinese Acad. of Sci. Shanghai 201800 China

The optical absorption properties of phase-change optical recording thin films subjected to various initialization conditions were investigated. The effects of initialization power and velocity on optical constants of the Ge2Sb2Te5 thin films were also studied. The energy gap of Ge2Sb2Te5 thin films subjected to various initialization conditions was also obtained. It was found that the optical energy gap of the Ge2Sb2Te5 thin films increased with either increasing initialization laser power or decreasing initialization velocity, with peak of 0.908 eV at laser power of 1000 mW or initialization velocity of 4.0 m/s, but the continued increasing initialization laser power or decreasing initialization velocity resulted in the decrease of the optical energy gap. The change of the optical energy gap was discussed on the basis of amorphous crystalline transformation.

关键词： Phase transformation optical recording Ge2Sb2Te5 optical absorption Energy gap

Identification of chemical compositions from“featureless”optical absorption spectra:Machine learning predictions and experimental validations

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Nano Research 2023年第3期16卷 4188-4196页

作者： Tiankai Chen Jiali Li Pengfei Cai Qiaofeng Yao Zekun Ren Yixin Zhu Saif Khan Jianping Xie Xiaonan Wang Department of Chemical and Biomolecular Engineering National University of Singapore4 Engineering Drive 4Singapore 117585Singapore Department of Materials Science and Engineering National University of Singapore9 Engineering Drive 1Singapore 117575Singapore Singapore-MIT Alliance for Research and Technology(SMART) 1 CREATE WaySingapore 138602Singapore Department of Chemical Engineering Tsinghua UniversityBeijing 100084China

Rapid and accurate chemical composition identification is critically important in *** it can be achieved with optical absorption spectrometry by comparing the experimental spectra with the reference data when the chemical compositions are simple,such application is limited in more complicated scenarios especially in nano-scale *** is due to the difficulties in identifying optical absorption peaks(i.e.,from“featureless”spectra)arose from the *** this work,using the ultraviolet-visible(UV-Vis)absorption spectra of metal nanoclusters(NCs)as a demonstration,we develop a machine-learningbased method to unravel the compositions of metal NCs behind the“featureless”*** implementing a one-dimensional convolutional neural network,good matches between prediction results and experimental results and low mean absolute error values are achieved on these optical absorption spectra that human cannot *** work opens a door for the identification of nanomaterials at molecular precision from their optical properties,paving the way to rapid and high-throughput characterizations.

关键词： gold nanoclusters composition identification optical absorption machine learning convolutional neural network

Exciton optical absorption in asymmetric ZnO/ZnMgO double quantum wells with mixed phases

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Chinese Physics B 2020年第7期29卷 456-463页

作者： Zhi-Qiang Han Li-Ying Song Yu-Hai Zan Shi-Liang Ban School of Physical Science and Technology Inner Mongolia UniversityHohhot 010021China

The optical absorption of exciton interstate transition in Zn1-xlMgxlO/ZnO/Zn1-xcMgxcO/ZnO/Zn1-xrMgxrO asymmetric double quantum wells(ADQWs)with mixed phases of zinc-blende and wurtzite in Zn1-xMgxO for 0.37optical absorption coefficients(OACs)of exciton interstate transition are obtained by the density matrix *** results show that Hartree potential bends the conduction and valence bands,whereas a BEF tilts the bands and the combined effect enforces electrons and holes to approach the opposite interfaces to decrease the Coulomb interaction effects between electrons and ***,the OACs indicate a transformation between direct and indirect excitons in zinc-blende ADQWs due to the quantum confinement *** are two kinds of peaks corresponding to wurtzite and zinc-blende structures respectively,and the OACs merge together under some special *** computed result of exciton interband emission energy agrees well with a previous *** conclusions are helpful for further relative theoretical studies,experiments,and design of devices consisting of these quantum well structures.

关键词： quantum well mixed phase exciton transition direct and indirect exciton optical absorption

Influences of hydrogen dilution on microstructure and optical absorption characteristics of nc-SiO_x:H film

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Chinese Physics B 2015年第10期24卷 547-552页

作者：赵蔚杜霖元蒋昭毅尹辰辰于威傅广生 Hebei Key Laboratory of Optic-electronic Information Materials College of Physics Science and TechnologyHebei University School of Science Hebei University of Engineering

By using the plasma enhanced chemical vapor deposition（PECVD） technique, amorphous silicon oxide films containing nanocrystalline silicon grain（nc-Si O x：H） are deposited, and the bonding configurations and optical absorption properties of the films are investigated. The grain size can be well controlled by varying the hydrogen and oxygen content,and the largest size is obtained when the hydrogen dilution ratio R is 33. The results show that the crystallinity and the grain size of the film first increased and then decreased as R increased. The highest degree of crystallinity is obtained at R = *** analyses of bonding characteristics and light absorption characteristics show that the incorporation of hydrogen leads to an increase of overall bonding oxygen content in the film, and the film porosity first increases and then decreases. When R = 30, the film can be more compact, the optical absorption edge of the film is blue shifted, and the film has a lower activation energy.

关键词： nc-SiOx:H microstructure optical absorption

Spatially nonlocal effects on optical absorption properties in coupled quantum wells with an applied electric field

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Chinese Physics B 2014年第12期23卷 398-403页

作者：王晁阳王光辉 Laboratory of Nanophotonic Functional Materials and Devices South China Normal University

Based on the microscopic nonlocal optical response theory, the intersubband optical absorption properties in AlGa As/Ga As couple quantum wells（CQWs） are investigated for p-polarized states. The numerical results show that spatial nonlocality of optical responses can induce a radiation shift on optical absorption spectra due to nonlocal effects. The dependence of the radiation shift on the CQW structure and the applied electric field is clarified. It is also demonstrated that the maximal radiation shift and the least optical absorbance can be obtained by adopting an appropriate CQW structure and a suitable applied electric field. This work may provide some methods of designing the nanomaterials with controllable nonlocality and observing the spatial nonlocal effects in experiment.

关键词： optical absorption coupled quantum well spatial nonlocality

Thermal bleaching of optical absorption and photoluminescence spectra of γ-irradiated CaF_2:Dy:Pb:Na single crystals

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Journal of Rare Earths 2010年第4期28卷 493-497页

作者： S.M. Moses Kennedy Department of Physics S.S.N. College of Engineering Rajiv Gandhi Salai Kalavakkam-603 110 Chennai Tamil Nadu India

The variation of the optical absorption (OA) and photoluminescence (PL) spectra with temperature was studied on γ-irradiated CaF2:Dy:Pb:Na single crystals. The OA spectrum showed bands around 2.05, 3.20, 3.82 and 6.20 eV which could be attributed to different sodium associated (SA) colour centres (CCs) such as MNa and RA+ . Heating the crystal indicated the annihilation and formation of different SACCs. The excitation spectrum for the characteristic Dy3+ emission at 2.14 eV immediately after irradiation was...

关键词： calcium fluoride optical absorption photoluminescence colour centres dysprosium lead sodium rare earths