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Impact of conduction band non-parabolicity and dielectric mismatch on photoionization cross section of donor bound polaron in spherical GaN/InN core-shell nanoparticle 传导带非抛物性和介电失配对球形GaN/InN核壳纳米粒子中供体束缚极化子光离截面的影响
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-18 DOI: 10.1051/epjap/2020200233
A. Talbi, M. Haouari, K. Nouneh, E. Feddi, M. Addou
Understanding the behavior of single dopant in semiconductors is a challenge to attain a high control on optoelectronic devices. Based on the fact that the external perturbations have an important impact on properties of doped nanocrystals, we have studied the simultaneous effects of phonons and conduction band non-parabolicity combined to dielectric mismatch and donor position on the photoionization cross section of an off-center donor in spherical GaN/InN core-shell quantum dots. The calculations were carried out within the framework of the effective-mass approximation and the eigenvalues equation has been solved using the Ritz variational method. The examination of the photoionization cross section, corresponding to the first donor energy level and the non-parabolic conduction band optical transition, shows clearly that the existence of non-parabolicity band or dielectric environment causes a blue shift of resonance peaks while the existence of phonon red shift them with a non-neglected variations in their intensity. The donor position has also an important effect on peaks position and amplitude.
了解半导体中单一掺杂剂的行为是实现光电器件高控制的一个挑战。基于外部扰动对掺杂纳米晶体性能的重要影响,我们研究了声子、导带非抛物性、介质失配和施主位置对球形GaN/InN核壳量子点中偏离中心施主的光离截面的同时影响。计算在有效质量近似的框架内进行,特征值方程采用里兹变分法求解。对第一给体能级和非抛物型导带光学跃迁对应的光电离截面的考察清楚地表明,非抛物型带或介质环境的存在导致共振峰蓝移,而声子的存在导致共振峰红移,且其强度变化不容忽视。供体位置对峰值位置和振幅也有重要影响。
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引用次数: 1
Nanosecond laser-induced breakdown assisted by femtosecond laser pre-ionization in air: the effect on spatial resolution and continuous radiation 空气中飞秒激光预电离辅助纳秒激光诱导击穿:对空间分辨率和连续辐射的影响
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-01 DOI: 10.1051/epjap/2020200258
Bo Li, Xiaofeng Li, Zhu Zhifeng, Q. Gao
Laser-induced breakdown spectroscopy (LIBS) is a powerful technique for quantitative diagnostics of gases. The spatial resolution of LIBS, however, is limited by the volume of plasma. Here femtosecond-nanosecond dual-pulsed LIBS was demonstrated. Using this method, the breakdown threshold was reduced by 80%, and decay of continuous radiation was shortened. In addition, the volume of the plasma was shrunk by 85% and hence, the spatial resolution of LIBS was significantly improved.
激光诱导击穿光谱(LIBS)是一种强有力的气体定量诊断技术。然而,LIBS的空间分辨率受到等离子体体积的限制。这里展示了飞-纳-秒双脉冲LIBS。采用该方法,击穿阈值降低80%,缩短了连续辐射的衰减时间。此外,等离子体体积缩小了85%,因此,LIBS的空间分辨率显着提高。
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引用次数: 1
New approach to study HTS bulk behavior for a fully superconducting motor design 研究全超导电机高温超导体行为的新方法
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-01 DOI: 10.1051/epjap/2020200031
H. Bouchekhou, H. Allag, M. Mekidèche, J. Lévêque, L. Gueraiche
The originality of this work is to applied Amperian Approach for modelling HTS bulk especially in electrical motor applications. This approach has proven its efficiency in electrical materials having a constant conductivity. For HTS materials, the resistivity change brutally and have a non linear comportment through any external magnetic field variations. To success the modelisation, we have to create an iterative procedure. All simulation steps are based on the power law model for computing resistivity and current densities adding the fixed point method for non linear iterations. The majority of our results concern the current densities in the HTS bulk rotor with different critical currents constatations under mgnetic field created by three phase coils of the proposed superconducting synchronous motor (SSM) prototype. Some results are consolidated by numerical way using flux 2D software.
这项工作的独创性是应用Amperian方法来模拟高温超导体,特别是在电动机应用中。这种方法在具有恒定导电性的电气材料中已被证明是有效的。高温超导材料的电阻率随外加磁场的变化变化剧烈,且呈非线性。为了成功建模,我们必须创建一个迭代过程。所有模拟步骤均基于幂律模型计算电阻率和电流密度,并加入不动点法进行非线性迭代。我们的大部分研究结果都是关于超导同步电动机原型在三相线圈产生的磁场下,具有不同临界电流稳态的高温超导体转子中的电流密度。利用flux 2D软件对部分结果进行了数值整合。
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引用次数: 1
Comparison of random field strengths in (1-x)SrTiO3-xBiFeO3 and (1-x)SrTiO3-xBaTiO3 relaxor ferroelectrics by means of acoustic emission 声发射法比较(1-x)SrTiO3-xBiFeO3和(1-x)SrTiO3-xBaTiO3弛豫铁电体随机场强
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-01 DOI: 10.1051/epjap/2020200075
E. Dul’kin, M. Roth
In relaxor (1-x )SrTiO3 -x BiFeO3 ferroelectrics ceramics (x  = 0.2, 0.3 and 0.4) both intermediate temperatures and Burns temperatures were successfully detected and their behavior were investigated in dependence on an external bias field using an acoustic emission. All these temperatures exhibit a non-trivial behavior, i.e. attain the minima at some threshold fields as a bias field enhances. It is established that the threshold fields decrease as x increases in (1-x )SrTiO3 -x BiFeO3 , as it previously observed in (1-x )SrTiO3 -x BaTiO3 (E. Dul'kin, J. Zhai, M. Roth, Phys. Status Solidi B 252 , 2079 (2015)). Based on the data of the threshold fields the mechanisms of arising of random electric fields are discussed and their strengths are compared in both these relaxor ferroelectrics.
在弛豫(1-x)SrTiO3 -x BiFeO3铁电陶瓷(x = 0.2, 0.3和0.4)中,成功地检测了中间温度和Burns温度,并利用声发射研究了它们依赖于外部偏置场的行为。所有这些温度都表现出非平凡的行为,即随着偏置场的增强,在某些阈值场达到最小值。在(1-x)SrTiO3 -x BiFeO3中,阈值场随着x的增加而减小,正如之前在(1-x)SrTiO3 -x BaTiO3中观察到的那样(E. Dul'kin, J. Zhai, M. Roth, Phys。固体状态B 252, 2079(2015))。根据阈值场的数据,讨论了随机电场的产生机理,并比较了两种弛豫铁电体中随机电场的强度。
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引用次数: 1
Effect of electrolyte solution and deposition methods on TiO2/CdS core–shell nanotube arrays for photoelectrocatalytic application 电解质溶液和沉积方法对TiO2/CdS核壳纳米管阵列光电催化性能的影响
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-01 DOI: 10.1051/EPJAP/2020200127
Selma M. H. Al-Jawad, N. Imran, M. R. Mohammad
In this work, TiO2 nanostructure thin films were deposited by using anodization technique, while CdS thin films were deposited on TiO2 films by two methods chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR). The structure of TiO2 /CdS films were investigated and analyzed by XRD, SEM, and AFM, but the optical properties were investigated by UV–visible spectroscopy, PL spectroscopy, and spectral response. XRD analysis of all deposited films has confirmed the formation of two phases one is tetragonal phase (anatase, and rutile) for TiO2 , and second hexagonal phase which belong to CdS layer. SEM images of TiO2 nanotubes arrays (NTAs)/CdS showed the TiO2 NTs walls become decorated with aggregates of fine CdS nanoparticles that partly penetrate into the TiO2 NTAs pores. AFM measurements displayed increase in the surface roughness compared with TiO2 films. PL measurement results of TiO2 /CdS core–shell show two peaks, one is located at UV-region pointed to energy band gap for TiO2 nano films, and second one is located at visible region pointing to recombination of photogenerated electron–hole pairs within CdS layers. Spectral response measurements showed photocurrent peaks for all TiO2 /CdS films deposited with different electrolyte solution have red-shift to visible region. When illuminated with a UV–Vis light source, the TiO2 /CdS core–shell films displayed high response. A higher response to UV–Vis light was attained with the use of TiO2 NTAs/CdS films prepared by anodization /CBD. This approach offers a technique for fabricating photoelectrodes.
本研究采用阳极氧化技术制备TiO2纳米结构薄膜,采用化学浴沉积(CBD)和连续离子层吸附反应(SILAR)两种方法在TiO2薄膜上制备CdS薄膜。采用XRD、SEM、AFM对TiO2 /CdS薄膜的结构进行了研究和分析,并通过紫外可见光谱、PL光谱和光谱响应对其光学性质进行了研究。对所有沉积膜的XRD分析证实,TiO2形成了两种相,一种是四方相(锐钛矿和金红石),另一种是六方相,属于CdS层。纳米TiO2纳米管阵列(NTAs)/CdS的SEM图像显示,纳米TiO2纳米管的内壁被精细的CdS纳米粒子聚集,这些纳米粒子部分渗透到纳米TiO2纳米管的孔中。AFM测量显示,与TiO2薄膜相比,表面粗糙度有所增加。TiO2 /CdS核壳的PL测量结果显示出两个峰,一个峰位于紫外区,指向TiO2纳米膜的能带隙,另一个峰位于可见光区,指向CdS层内光生电子空穴对的复合。光谱响应测量表明,不同电解质溶液沉积的TiO2 /CdS薄膜的光电流峰都有红移到可见光区。在紫外可见光源照射下,TiO2 /CdS核壳膜表现出高响应。采用阳极氧化/CBD法制备的TiO2 NTAs/CdS薄膜对UV-Vis光具有较高的响应。这种方法提供了一种制造光电极的技术。
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引用次数: 3
Superlensing property of 2-D glass photonic crystal 二维玻璃光子晶体的超透镜特性
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-01 DOI: 10.1051/EPJAP/2020200237
R. Ghosh, R. Chakraborty
A two dimensional square lattice photonic crystal (PhC) formed by placing glass matrix in air is proposed for subwavelength imaging around 840 nm. The superlensing behavior at relatively lower wavelength compared to other reported PhC superlens is obtained by this configuration. Other advantages of using glass is that they have lower optical absorption at this wavelength and is relatively cheap. By placing the proposed PhC arrangement between the object and the objective of a conventional optical microscope, superlensing effect can be realized. Moreover, any change in radius of glass rod during fabrication process can result in the shift of superlensing wavelength.
提出了一种将玻璃基体置于空气中形成的二维方形晶格光子晶体(PhC),用于840nm左右的亚波长成像。与其他已报道的PhC超透镜相比,通过这种结构获得了相对较低波长的超透镜行为。使用玻璃的其他优点是它们在该波长具有较低的光吸收并且相对便宜。通过在物镜和物镜之间放置所提出的PhC排列,可以实现超透镜效应。此外,在制造过程中,玻璃棒半径的任何变化都会导致超透镜波长的偏移。
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引用次数: 0
Plasmon-assisted interaction of Si with light, for cancer hyperthermia and electromagnetic energy harvest 等离子体辅助硅与光的相互作用,用于癌症热疗和电磁能量收集
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-01 DOI: 10.1051/epjap/2020200071
B. Mousavi, Morteza Rezaei Talarposhti, F. Karbassian, A. Mousavi
Metal-assisted chemical etching (MACE) is applied for fabrication of silicon nanowires (SiNWs). We have shown the effect of amorphous sheath of SiNWs by treating the nanowires with SF6 and the resulting reduction of absorption bandwidth, i.e. making SiNWs semi-transparent in near-infrared (IR). For the first time, by treating the fabricated SiNWs with copper containing HF∕H2O2∕H2O solution, we have generated crystalline nanowires with broader light absorption spectrum, up to λ = 1 μm. Both the absorption and photo-luminescence (PL) of the SiNWs are observed from visible to IR wavelengths. It is found that the SiNWs have PL at visible and near Infrared wavelengths, which may infer presence of mechanisms such as forbidden gap transitions other can involvement of plasmonic resonances. Non-radiative recombination of excitons is one of the reasons behind absorption of SiNWs. Also, on the dielectric metal interface, the absorption mechanism can be due to plasmonic dissipation or plasmon-assisted generation of excitons in the indirect band-gap material. Comparison between nanowires with and without metallic nanoparticles has revealed the effect of nanoparticles on absorption enhancement. The broader near IR absorption, paves the way for applications like hyperthermia of cancer while the optical transition in near IR also facilitates harvesting electromagnetic energy at a broad spectrum from visible to IR.
金属辅助化学蚀刻(MACE)技术被应用于硅纳米线的制备。我们通过用SF6处理纳米线,证明了SiNWs的非晶态护套的影响,并由此降低了吸收带宽,即使SiNWs在近红外(IR)中半透明。首次用含HF∕H2O2∕H2O的铜溶液处理制备的SiNWs,制备出具有更宽光吸收光谱的晶体纳米线,吸收光谱可达λ = 1 μm。从可见光波段到红外波段都观察到了sinw的吸收和光致发光。发现SiNWs在可见光和近红外波段具有PL,这可能推断出存在诸如禁止间隙跃迁等机制,而这些机制可能涉及等离子体共振。激子的非辐射复合是sinw吸收的原因之一。此外,在介电金属界面上,吸收机制可能是由于间接带隙材料中的等离子体耗散或等离子体辅助激子的产生。通过对纳米线加金属纳米粒子和不加金属纳米粒子的比较,揭示了纳米粒子对吸收增强的作用。更广泛的近红外吸收为癌症热疗等应用铺平了道路,而近红外的光学跃迁也有利于从可见到红外的广谱电磁能量的收集。
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引用次数: 0
Thermohydraulic characteristics and entropy analysis of a novel clockwise and anti-clockwise twisted sinusoidal wavy micro-channel under pulsating inlet condition 一种新型顺、逆时针扭曲正弦波微通道在脉动进口条件下的热液特性及熵分析
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-01 DOI: 10.1051/epjap/2020200176
S. Bhattacharyya, S. Das, H. Chattopadhyay
Heat transfer performance of microchannel are becoming an important area of research with the current fast growing scenario of high speed computing and miniaturized electronic devices. These devices pile up large amount of heat accompanied by smaller surface area to release it. The current work examines unsteady, laminar flow heat transfer inside a novel twisted sinusoidal wavy microchannel. The channel with square cross section is wavy in nature as well as twisted. The first half portion of the channel is twisted clockwise, whereas the twist in the remaining part is having counterclockwise twist. The novel geometry promotes mixing of fluid layers leading to transport augmentation. The inlet pulsation follows sinusoidal pattern in time. The thermal performance parameter of the proposed novel geometry was assessed within a Reynolds number range of 1–100. Both the pulsation amplitude and Strouhal number are varied during the course of this study. To solve the governing equations, a finite volume based method was utilized. The Nusselt number data shows significant enhancement for the sinusoidal inlet velocity as compared to that of the steady case, i.e. without inlet flow pulsation. The performance enhancement criterion combining heat transfer and pressure drop shows significant improvement over steady flow case as well as for one-way twisted tube. Entropy generation, which is the measure of dissipated energy, is also reported in the present work.
随着高速计算和电子器件小型化的快速发展,微通道的传热性能已成为一个重要的研究领域。这些装置可以堆积大量的热量,同时可以用较小的表面积来释放热量。本文研究了一种新型扭曲正弦波微通道内的非定常层流传热。横截面为方形的沟道,既有波浪形,又有扭曲。所述通道的前半部分为顺时针扭转,而所述其余部分中的扭转具有逆时针扭转。新颖的几何结构促进了流体层的混合,从而增加了输运。入口脉动在时间上呈正弦型。所提出的新几何形状的热性能参数在1-100的雷诺数范围内进行了评估。在研究过程中,脉动幅度和斯特罗哈尔数都发生了变化。采用基于有限体积的方法求解控制方程。努塞尔数数据显示,与稳定情况(即没有进口流动脉动)相比,正弦进口速度有显著增强。换热与压降相结合的性能增强准则在稳态工况和单向扭管工况下均有显著改善。熵的产生,这是耗散能量的量度,也报道在本工作中。
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引用次数: 8
Enhancement of the performance of CdS/CdTe heterojunction solar cell using TiO2/ZnO bi-layer ARC and V2O5 BSF layers: A simulation approach 利用TiO2/ZnO双层ARC和V2O5 BSF层增强CdS/CdTe异质结太阳能电池的性能:模拟方法
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-01 DOI: 10.1051/epjap/2020200213
A. Kuddus, Md. Ferdous Rahman, J. Hossain, A. Ismail
This article presents the role of Bi-layer anti-reflection coating (ARC) of TiO2 /ZnO and back surface field (BSF) of V2 O5 for improving the photovoltaic performance of Cadmium Sulfide (CdS) and Cadmium Telluride (CdTe) based heterojunction solar cells (HJSCs). The simulation was performed at different concentrations, thickness, defect densities of each active materials and working temperatures to optimize the most excellent structure and working conditions for achieving the highest cell performance using obtained optical and electrical parameters value from the experimental investigation on spin-coated CdS, CdTe, ZnO, TiO2 and V2 O5 thin films deposited on the glass substrate. The simulation results reveal that the designed CdS/CdTe based heterojunction cell offers the highest efficiency, η of ∼25% with an enhanced open-circuit voltage, V oc of 0.811 V, short circuit current density, J sc of 38.51 mA cm−2 , fill factor, FF of 80% with bi-layer ARC and BSF. Moreover, it appears that the TiO2 /ZnO bi-layer ARC, as well as ETL and V2 O5 as BSF, could be highly promising materials of choice for CdS/CdTe based heterojunction solar cell.
本文介绍了TiO2 /ZnO双层增透涂层(ARC)和V2 O5背表面场(BSF)在提高硫化镉(cd)和碲化镉(CdTe)基异质结太阳能电池(HJSCs)光伏性能中的作用。通过对沉积在玻璃基板上的自旋镀膜cd、CdTe、ZnO、TiO2和V2 O5薄膜的光学和电学参数值进行实验研究,在不同浓度、厚度、缺陷密度和工作温度下进行了模拟,以优化最优的结构和工作条件,以实现最高的电池性能。仿真结果表明,所设计的CdS/CdTe异质结电池具有最高的效率,在提高开路电压的情况下η为~ 25%,V oc为0.811 V,短路电流密度,jsc为38.51 mA cm−2,填充系数,FF为80%,具有双层ARC和BSF。此外,TiO2 /ZnO双层ARC,以及ETL和V2 O5作为BSF,可能是CdS/CdTe基异质结太阳能电池非常有前途的材料选择。
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引用次数: 11
The activation energy U(T,B) in high temperature superconductor 高温超导体的活化能U(T,B)
IF 1 4区 物理与天体物理 Q3 Physics and Astronomy Pub Date : 2020-11-01 DOI: 10.1051/epjap/2020200223
A. Labrag, M. Bghour, Ahmed Abou El Hassan, Habiba El Hamidi, A. Taoufik, Said Laasri
It is reported in this paper on the thermally assisted flux flow in epitaxial YBa2 Cu3 O7-δ deposited by Laser ablation method on the SrTiO3 substrate. The resistivity measurements ρ  (T , B ) of the sample under various values of the magnetic field up to 14T in directions B ∥ab-plane and B ∥c -axis with a dc weak transport current density were investigated in order to determine the activation energy and then understand the vortex dynamic phenomena and therefore deduce the vortex phase diagram of this material. The apparent activation energy U 0  (B ) calculated using an Arrhenius relation. The measured results of the resistivity were then adjusted to the modified thermally assisted flux flow model in order to account for the temperature-field dependence of the activation energy U  (T , B ). The obtained values from the thermally assisted activation energy, exhibit a behavior similar to the one showed with the Arrhenius model, albeit larger than the apparent activation energy with ∼1.5 order on magnitude for both cases of the magnetic field directions. The vortex glass model was also used to obtain the vortex-glass transition temperature from the linear fitting of [d  ln ρ /dT  ] −1 plots. In the course of this work thanks to the resistivity measurements the upper critical magnetic field H c 2  (T ), the irreversibility line H irr  (T ) and the crossover field H CrossOver  (T ) were located. These three parameters allowed us to establish a phase diagram of the studied material where limits of each vortex phase are sketched in order to optimize its applicability as a practical high temperature superconductor used for diverse purposes.
本文报道了激光烧蚀法在SrTiO3衬底上沉积YBa2 cu3o7 -δ外延材料的热助磁流。研究了在直流弱输运电流密度下,在高达14T的不同磁场值下,试样在B∥ab-平面和B∥c -轴方向上的电阻率ρ (T, B)测量,以确定活化能,了解涡旋动力学现象,从而推导出该材料的涡旋相图。用Arrhenius关系式计算表观活化能u0 (B)。然后将电阻率的测量结果调整为修正的热辅助通量流模型,以考虑活化能U (T, B)的温度场依赖性。从热辅助活化能中得到的值,表现出与Arrhenius模型相似的行为,尽管在磁场方向的两种情况下都比表观活化能大约1.5个数量级。通过对[d ln ρ /dT]−1曲线的线性拟合,利用旋涡玻璃模型得到了旋涡玻璃转变温度。在此过程中,通过电阻率测量确定了上部临界磁场h2 (T)、不可逆性线hirr (T)和交叉场H crossover (T)。这三个参数使我们能够建立所研究材料的相图,其中每个涡旋相的极限都被勾画出来,以便优化其作为用于各种用途的实际高温超导体的适用性。
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引用次数: 5
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