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Negative Thermal Transport in Conduction and Advection

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Chinese physics Letters 2020年第8期37卷 19-24页

作者： Liujun Xu Jiping Huang Department of physics State Key Laboratory of Surface Physicsand Key Laboratory of Micro and Nano Photonic Structures(MOE)Fudan UniversityShanghai 200438China

Negative refractive index has drawn a great deal of attention due to its unique properties and practical applications in wave *** promote the related physics in thermotics,here we manage to coin a complex thermal conductivity whose imaginary part corresponds to the real part of complex refractive ***,the thermal counterpart of negative refractive index is just negative imaginary thermal conductivity,which is featured by the opposite directions of energy flow and wave vector in thermal conduction and advection,thus called negative thermal transport *** avoid violating causality,we design an open system with energy exchange and explore three different cases to reveal negative thermal *** further provide experimental suggestions with a solid ring *** finite-element simulations agree with theoretical analyses,indicating that negative thermal transport is physically *** results have potential applications such as designing the inverse Doppler effect in thermal conduction and advection.

关键词： structure. imaginary refractive

Thickness dependence of grain size and surface roughness for dc magnetron sputtered Au films

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Chinese physics B 2010年第8期19卷 506-509页

作者：张鑫宋小会张殿琳 Beijing National laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of Sciences

The grain size and surface morphology of sputtered Au films are studied by x-ray diffraction and atomic force microscope. For as-deposited samples the grain growth mechanism is consistent with the two-dimensional （2D） theory, which gives relatively low diffusion coefficient during deposition. Annealing process demonstrates the secondary grain growth mechanism in which the thickness dependence of grain boundary energy plays a key role. The surface roughness increases with the increase of grain size.

关键词： grain size surface morphology Au film magnetron sputtering

Influence of applied electric field on the absorption coefficient and subband distances in asymmetrical AlN/GaN coupled double quantum wells

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Chinese physics B 2009年第9期18卷 3905-3908页

作者：岑龙斌沈波秦志新张国义 State Key laboratory of Artificial Microstructure and Mesoscopic physics School of PhysicsPeking University

The influence of applied electric fields on the absorption coefficient and subband distances in asymmetrical A1N/GaN coupled double quantum wells （CDQWs） has been investigated by solving SchrSdinger and Poisson equations self-consistently. It is found that the absorption coefficient of the intersubband transition （ISBT） between the ground state and the third excited state （lodd - 2even） can be equal to zero when the electric fields are applied in asymmetrical A1N/GaN CDQWs, which is related to applied electric fields induced symmetry recovery of these states. Meanwhile, the energy distances between 1odd - 2even and 1even - 2even subbands have different relationships from each other with the increase of applied electric fields due to the different polarization-induced potential drops between the left and the right wells. The results indicate that an electrical-optical modulator operated within the opto-communication wavelength range can be realized in spite of the strong polarization-induced electric fields in asymmetrical A1N/GaN CDQWs.

关键词： A1N/GaN CDQWs electrical-optical modulator intersubband transition

Effects of growing conditions on the electric and magnetic properties of strained La_(2/3)Sr_(1/3)MnO_3 thin films

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Chinese physics B 2015年第2期24卷 419-423页

作者：卢海霞王晶沈保根孙继荣 Beijing National laboratory for Condensed Matter physics and the Institute of physics Chinese Academy of Sciences

We investigate the growing condition dependences of magnetic and electric properties of the La2/3Sr1/3MnO3 thin films grown on SrTiO3（001） *** reducing the film thickness and growth pressure,the Curie temperature（Tc）drops off,and the magnetism and metallicity are *** an appropriate deposition temperature,we can obtain the best texture and remarkably enhance the magnetic and electrical ***,the resistivity of film cannot be modulated by changing the dc current and green light *** result may be induced by the coherent strains in the epitaxially grown film due to its lattice mismatching that of the SrTiO3 ***,we show that the relations between the magnetism and the resistivity for the typical films with different thickness *** the 13.4-nm-thick film,the R-T curve presents two transition behaviors：insulator-to-metal and metal-to-insulator in the cooling process：the former corresponds to magnetic transition,and the later correlates with thermal excitation conduction.

关键词： growing condition magnetism resistivity

Growth of N-polar GaN on vicinal sapphire substrate by metal organic chemical vapor deposition

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Rare Metals 2014年第6期33卷 709-713页

作者： Can-Tao Zhong Guo-Yi Zhang State Key laboratory of Artificial Microstructure and Mesoscopic physics School of Physics Peking University

The growth and properties of N-polar Ga N layers by metal organic chemical vapor deposition（MOCVD） were reported. It is found that N-polar Ga N grown on normal sapphire substrate shows hexagonal hillock surface morphology. With the misorientation angles increasing from 0.5° to 2.0° toward the a-plane of the sapphire substrate, the number of the hillock becomes less and less and finally the surface becomes flat one on the sapphire substrate with the misorientation angle of 2°. It is also found that the crystalline quality and the strain in the Ga N are greatly influenced by the misorientation angle.

关键词： GaN N-polarity Metal organic chemical vapor deposition

Interband Optical Transitions due to Donor Bound Excitons in Wurtzite InGaN Strained Coupled Quantum Dots： Strong Built-in Electric Field Effects

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Chinese physics Letters 2006年第8期23卷 2206-2209页

作者：池月萌史俊杰 State Key laboratory for Mesoscopic physics and School of Physics Peking University Beijing 100871

Considering the three-dimensional confinement of the electrons and holes and the strong built-in electric field （BEF） in the wurtzite InGaN strained coupled quantum dots （QDs）, the positively charged donor bound exciton states and interband optical transitions are investigated theoretically by means of a variational method. Our calculations indicate that the emission wavelengths sensitively depend on the donor position, the strong BEF, and the structure parameters of the QD system.

关键词： LIGHT-EMITTING-DIODES SPONTANEOUS POLARIZATION WELL WIRES GAN INDIUM NITRIDE SINGLE STATES

Synthesis and properties of bulk nanocrystalline Mg_2Si through ball-milling and reactive hot-pressing

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中国有色金属学会会刊：英文版 2006年第5期16卷 987-991页

作者：熊伟秦晓英孔明光陈莉 Key laboratory of Materials physics Institute of Solid State PhysicsChinese Academy of Sciences

Bulk nanocrystalline Mg2Si(n-Mg2Si) was prepared by mechanical milling and reactive hot-pressing in vacuum and its mechanical properties were characterized. The results indicate that the grain sizes of Mg and Si decrease non-monotonously with increasing ball-to-powder mass ratio(BPR). The content of Mg2Si phase increases with increasing milling time; however, pure Mg2Si phase cannot be obtained by direct ball milling. Moreover, monolithic is Mg2Si phase can only be obtained when as much as 10% of excess Mg was blended in the raw mixtures. The relative density (D) and fracture toughness as well as hardness of bulk Mg2Si samples can be raised effectively by increasing the pressure in hot-pressing. After hot-pressing at 400 ℃ for 60 min under 1.5 GPa, highly dense(D>98%) n-Mg2Si (d=60 nm) was obtained, whose fracture toughness (KIC≈1.46 MPa·m1/2) and Vickers hardness (HV≈ 4.38 Gpa) are superior to those of conventional coarse-grained Mg2Si.

关键词： Mg2Si 纳米晶体球磨热压机械性能

Helium Plasma Effects on Polymer Surfaces:from Plasma Parameters and Surface Properties towards Bioengineering Applications

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Chinese Journal of Polymer Science 2024年第8期42卷 1156-1166页

作者： Andrei Vasile Nastuta Maria Butnaru Byron Cheatham Ramona Huzum Vasile Tiron Ionut Topala physics and Biophysics Education Research laboratory(P&B-EduResLab) Biomedical Science DepartmentFaculty of Medical Bioengineering‘Grigore T.Popa’University of Medicine and Pharmacy IasiM.Kogalniceanu 9-13Iasi 700454Romania Faculty of Medical Bioengineering ‘Grigore T.Popa’University of Medicine and Pharmacy IasiM.Kogalniceanu 9-13Iasi 700454Romania Cytoviva Inc.570 Devall Drive Suite 301Auburn 36832ALUSA Integrated Center of Environmental Science Studies in the North-Eastern Development Region(CERNESIM) Department of Exact and Natural SciencesInstitute of Interdisciplinary Research‘Alexandru Ioan Cuza’University of IasiBlvd.Carol I no.11Iasi 700506Romania Research Center on Advanced Materials and Technologies(RAMTECH) Department of Exact and Natural SciencesInstitute of Interdisciplinary Research‘Alexandru Ioan Cuza’University of IasiBlvd.Carol I no.11Iasi 700506Romania Iasi Plasma Advanced Research Center(IPARC) Faculty of Physics‘Alexandru Ioan Cuza’University of IasiBlvd.Carol I no.11Iasi 700506Romania

Plasma treatment is necessary to optimize the performance of biomaterial *** enhances and regulates the performance of biomaterial su rfaces,creating an effective interface with the human *** treatments have the ability to modify the chemical com position and physical structu re of a surface while leaving its properties *** possess the ability to modify material su rfaces,eliminate contaminants,conduct investigations on cancer therapy,and facilitate wound *** subject of study in question involves the integration of plasma science and technology with biology and *** a helium plasma jet source,applying up to 18 kV,with an average power of 10 W,polymer foils were treated for 60 *** treatment has the ability to alter the chemical composition and physical structure of a su rface while maintaining its *** investigation involved the application of helium plasma at atmospheric pressure to polyamide 6 and polyethylene terephthalate *** inquiry involves monitoring and assessing the plasma source and polymer materials,as well as analyzing the impacts of plasma *** the mean power of the discharge aids in assessing the economic efficacy of the plasma *** discharge in helium at atmospheric pressure has beneficial effects in technology,where it increases the surface free energy of polymer *** biomedicine,it is used to investigate cytotoxicity and cell survival,particularly in direct blood exposure situations that can expedite *** the specific parameters that influence the plasma source in the desired manner for the intended application is of utmost im portance.

关键词： Atmopheric pressure plasmas Plasma-polymer interaction Plasma Medicine Plasma diagnosis Polymer characterization

Low lattice thermal conductivity and enhanced thermoelectric performance of SnTe via chemical electroless plating of Ag

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Rare Metals 2022年第1期41卷 86-95页

作者： Bang-Zhou Tian Xu-Ping Jiang Jie Chen Han Gao Ze-Gao Wang Jun Tang Da-Li Zhou Lei Yang Zhi-Gang Chen School of Materials Science&Engineering Sichuan UniversityChengdu 610064China Key laboratory of Material physics of Ministry of Education School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China Key laboratory of Radiation physics and Technology Ministry of EducationInstitute of Nuclear Science and TechnologySichuan UniversityChengdu 610064China Centre for Future Materials University of Southern QueenslandSpringfield CentralQLD 4300Australia

Interface engineering has been regarded as an effective strategy to manipulate the thermoelectric performance of ***,we use a facile chemical electroless plating and a spark plasma sintering process to fabricate Ag-plated SnTe *** sintering,a small amount of plated Ag can be doped into SnTe to suppress the Sn vacancies and the others form Ag precipitates with a size distribution from nanoscale to microscale,which introduces Ag/SnTe interfaces to enhance the Seebeck coefficient via energy filtering ***,these structures result in strong scattering to reach a low lattice thermal conductivity of-0.62 W·m^(–1)·K^(–1).Consequently,a maximum figure of merit(zT)of-0.67 at 823 K is achieved in 2 wt%Ag-plated SnTe,which is-60%higher than that of pristine ***,the microhardness indentation test results show that the mean microhardness of 2 wt%Ag-plated SnTe is HV 64.26,which is much higher than that of pristine SnTe,indicating that Ag electroless plating can improve the mechanical properties of *** work has provided a facile and eco-friendly method to realize the interface engineering for manipulating the thermoelectric and mechanical properties of SnTe.

关键词： Thermoelectric SnTe Electroless plating Energy filtering effect Interface engineering