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Journal of Semiconductors 2024年第9期 34-42页

作者： Leonarde do Nascimento Rodrigues Wesley Fiorio lnoch Marcos L.F.Gomes Odilon D.D.Couto Jr. Bráulio S.Archanjo Sukarno Olavo Ferreira Physics department Federal University of Vi?osa instituto de Física gleb wataghin Universidade Estadual de Campinas National Institute of Metrology Quality and Technology (Inmetro) Materials Metrology Division (DIMAT)

This work shows that despite a lattice mismatch of almost 20%, CdMnTe/CdTe/CdMnTe heterostructures grown directly on Si(111) have surprisingly good optical emission properties. The investigated structures were grown by molecular beam epitaxy and characterized by scanning transmission electron microscopy, macro-and micro-photoluminescence. Low temperature macro-photoluminescence experiments indicate three emission bands which depend on the CdTe layer thickness and have different confinement characteristics. Temperature measurements reveal that the lower energy emission band (at 1.48 eV)is associated to defects and bound exciton states, while the main emission at 1.61 eV has a weak 2D character and the higher energy one at 1.71 eV has a well-defined (zero-dimensional, 0D) 0D nature. Micro-photoluminescence measurements show the existence of sharp and strongly circularly polarized (up to 40%) emission lines which can be related to the presence of Mn in the heterostructure. This result opens the possibility of producing photon sources with the typical spin control of the diluted magnetic semiconductors using the low-cost silicon technology.

关键词：

Localized-states quantum confinement induced by roughness in CdMnTe/CdTe heterostructures grown on Si(111) substrates

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Journal of Semiconductors 2024年第9期45卷 28-35页

作者： Leonarde N.Rodrigues Wesley F.Inoch Marcos L.F.Gomes Odilon D.D.Couto Jr. Bráulio S.Archanjo Sukarno O.Ferreira Physics department Federal University of ViçosaViçosa36570-900Minas GeraisBrazil instituto de Física gleb wataghin Universidade Estadual de CampinasCampinas13083-859São PauloBrazil National Institute of Metrology Quality and Technology(Inmetro) Materials Metrology Division(DIMAT)Xerém2525-020Rio de JaneiroBrazil

关键词： CdMnTe/CdTe/CdMnTe heterostructure CdTe/CdMnTe quantum emitters quantum dot-like emission silicon(111)substrate

ZnO/CeO_(2)/carbon xerogel composites with direct Z-scheme heterojunctions:Enhancing photocatalytic remediation of 4-chlorophenol under visible light

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Journal of Rare Earths 2024年第2期42卷 314-322,I0003页

作者： Nicolas Perciani de Moraes Maite Birkett de Campos Sanmartin Robson da Silva Rocha Abner de Siervo Marcos Roberto de Vasconcelos Lanza D.Amaranatha Reddy Lianqing Yu Liana Alvares Rodrigues Escola de Engenharia de Lorena-EEL/USP Estrada Municipal do Campinho S/NCEP 12602-810LorenaSao PauloBrazil Institute of Physics"gleb wataghin" Applied Physics DepartmentState University of Campinas13083-859CampinasSPBrazi instituto de Quimica de Sao Carlos Universidade de Sao PauloAv.Trab.Sao Carlense400-Parque Arnold SchimidtSao CarlosSP13566-590Spain department of Sciences Indian Institute of Information Technology Design and ManufacturingKurnoolAndhra Pradesh518007India School of Materials Science and Engineering China University of PetroleumQingdao266580China

This paper aims to create visible light driven ternary photocatalysts using zinc oxide(ZnO),cerium(IV)oxide(CeO_(2)),and carbon xerogel(CX) as constituent *** use of CeO_(2) is based on the creation of direct-Z-scheme heterojunctions with the ZnO and the consequent diminishing of charge recombination,whereas the carbon xerogel inclusion is predicted to minimize bandgap energy,decrease electro n-hole reco mbination,and boost specific surface *** re,the choice of the black-wattle tannin as a carbonaceous precursor was targeted at the development of an environmentally friendly and affordable *** existence of the hexagonal phase of zinc oxide and cubic structure of the cerium(IV) oxide in the ternary material was confirmed by X-ray diffractometry and X-ray photoelectron spectroscopy,with the latter also suggesting chemical bonding between the ZnO and the CX due to the creation of zinc oxycarbide *** inclusion of the carbon xerogel provokes a significant modification in the morphology of the ternary material,resulting in an increased surface area and smaller particle *** CX/ZnO-CeO_(2) ternary composite obtains the highest photocatalytic efficiency among all the materials studied,degrading 100% of 4-chlorophenol under simulated sunlight and 68% under visible radiation,after 5 *** increased photocatalytic activity can be attributed to the formation of direct Z-scheme heterojunctions between the semiconductors,higher visible light response,and higher specific surface area,as evidenced by the results obtained by active radical scavenging,chronoamperometry,diffuse reflectance spectroscopy,and N_(2) adsorption-desorption isotherms.

关键词： Zinc oxide Cerium(Ⅳ)oxide Carbon xerogel Photocatalysis Direct Z-scheme heterojunction 4-Chlorophenol Rare earths

Magnetizations and magneto-transport properties of Ni-doped PrFeO_3 thin films

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Chinese Physics B 2014年第4期23卷 608-615页

作者： Feroz A.Mir S.K.Sharma Ravi Kumar University Science Instrumentation Center University of Kashmir instituto de fisica gleb wataghin Universidade Estadual de Campinas (UNICAMP) CMSE National Institute of Technology

The present study reports the magnetizations and magneto-transport properties of PrFel_xNixO3 thin films grown by pulsed laser ablation technique on LaA103 snbstrates. From DC M/H plots of these films, weak ferromagnetism or ferrimagnetism behaviors are observed. With Ni substitution, reduction in saturation magnetization is also seen. With Ni doping, variations in saturation field （Hs）, coercive field （Hc）, Weiss temperature （0）, and effective magnetic moment （Pelf） are seen. A small change of magnetoresitance with application of higher field is observed. Various essential parameters like density of state （Nf） at Fermi level, Mott＇s characteristic temperature （To）, and activation energy （Ea） in the presence of and in the absence of magnetic field are calculated. The present observed magnetic properties are related to the change of Fe-O bond length （causing an overlap between the oxygen p orbital and iron d orbital） and the deviation of the Fe-O-Fe angle from 180~. Reduction of magnetic domain after Ni doping is also explored to explain the present observed magnetic behavior of the system. The influence of doping on various transport properties in these thin films indicates a distortion in the lattice structure and single particle band width, owing to stress-induced reduction in unit cell volume.

关键词： thin films magnetization ferromagnetism ferrimagnetism magneto-transport and distortion

Sample Size dependence of Second Magnetizaion Peak in Type-ⅡSuperconductors

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Tsinghua Science and Technology 2003年第3期8卷 370-378页

作者： J.H.S.Torres Y.Kopelevich Institute de fisica"gleb wataghin" Universitade Estadual de CampinasUnicamp 13083-970CampinasSao PauloBrasilInstitute de fisica"Gleb Wataghin"Universitade Estadual de CampinasUnicamp 13083-970CampinasSao PauloBrasil

We show that the second magnetization peak(SMP),i.e.,an increase in the magnetization hysteresis loop width in type-11 superconductors,vanishes for samples smaller than a critical size,We argue that the SMP is not related to the critical current enhancement but can be well explainde within a frameword of the thermomagenetic flux-jump in stability theory,where flux jumps reduce the absolute irreversible magnetization relative to the isothermal critical state value at low enough magnetic *** recovering of the isothermal critical sate with increasing field leads to the *** low-field SMP takes place in both *** and high**** *** results show that the rsstoration of the isothermal critical state is rsponsible for the SMP occurrence in both cases.

关键词： Superconductor flux pinning and creep peekeffect phase transityons

RCD Large Aspect-Ratio Tokamak Equilibrium with Magnetic Islands:a Perturbed Approach

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Communications in Theoretical Physics 2013年第3期59卷 375-378页

作者： F.L.Braga instituto de Física gleb wataghin Departamento de Física AplicadaUniversidade Estadual de CampinasCampinasSP13083-859Brasil instituto Federal de Ci encias e Tecnologia do Esp' rito Santo Campus Santa TeresaES29600-000Brasil

Solutions of Grad-Shafranov （CS） equation with Reversed Current density （RCD） profiles present mag- netic islands when the magnetic flux is explicitly dependent on the poloidal angle. In this work it is shown that a typical cylindrical （large aspect-ratio） RCD equilibrium configuration perturbed by the magnetic field of a circular loop （simulating a divertor） is capable of generate magnetic islands, due to the poloidal symmetry break of the GS equilibrium solution.

关键词： symmetry break magnetic islands Grad-Shafranov equation reversed current density

Nano-fried-eggs： Structural, optical, and magnetic characterization of physically prepared iron-silver nanoparticles

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Nano Research 2018年第11期11卷 6074-6085页

作者： Julien Ramade Nicolas Troc Olivier Boisron Michel Pellarin Marie-Ange Lebault Emmanuel Cottancin Vitor T. A. Oiko Rafael Cabreira Gomes Varlei Rodrigues Matthias Hillenkamp Univ. Lyon Universitd Claude Bernard Lyon I CNRS UMR5306 Institut Lumiee Matiee t=-69622 Villeurbanne France instituto de F[sica gleb wataghin UNICAMP CP 6165 13083-970 Campinas SP Brazil

The prospect of combining both magnetic and plasmonic properties in a single nanoparticle promises both valuable insights on the properties of such systems from a fundamental viewpoint and numerous possibilities for technological applications. However, the combination of two of the most prominent metallic candidates—iron and silver—has presented numerous experimental difficulties because their thermodynamic properties impede miscibility and even coalescence. Herein, we present the thorough characterization of physically prepared Fe50Ag50 nanoparticles embedded in carbon and silica matrices via electron microscopy, optical spectroscopy, magnetometry and synchrotron-based X-ray spectroscopy. Iron and silver segregate completely into structures resembling fried eggs, with a nearly spherical, crystallized silver part surrounded by an amorphous structure of iron carbide or oxide, depending on the environment of the particles. Consequently, the particles exhibit both plasmonic absorption corresponding to the silver nanospheres in an oxide environment and a reduced but measurable magnetic response. The suitability of such nanoparticles for technological applications is discussed from the viewpoint of their high chemical reactivity with their environment.

关键词： nanoalloy bimetallic nanoparticles iron silver FeAg optical spectroscopy magnetometry

MHD Equilibrium with Reversed Current density and Magnetic Islands Revisited:the Vacuum Vector Potential Calculus

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Plasma Science and Technology 2013年第10期15卷 985-988页

作者： F.L.BRAGA gleb-wataghin Physics Institute Applied Physics DepartmentState University of Campinas Federal Institute of Science and Technology of Espirito Santo

The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that it is possible to determine a magnetohydrodynamic （MHD） equilibrium with reversed current density （RCD） profiles that presents magnetic islands. In this work we show analytical MHD equilibrium with a RCD profile and analyze the structure of the vacuum vector potential associated with these equilibria using the virtual casing principle.

关键词： magnetohydrodynamics vacuum vector potential reversed current density magnetic islands

Pushing the Band Gap Envelope of Quasi-Type II Heterostructured Nanocrystals to Blue:ZnSe/ZnSe_(1-X)Te_(X)/ZnSe Spherical Quantum Wells

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Energy Material Advances 2021年第1期2021卷 285-294页

作者： Jun Hyuk Chang Hak June Lee Seunghyun Rhee Donghyo Hahm Byeong Guk Jeong Gabriel Nagamine Lazaro APadilha Kookheon Char Euyheon Hwang Wan Ki Bae SKKU Advanced Institute of Nano Technology Sungkyunkwan UniversitySuwon 16419Republic of Korea School of Chemical and Biological Engineering Seoul National UniversitySeoul 08826Republic of Korea instituto de fisica“gleb wataghin” Universidade Estadual de CampinasUNICAMPP.O.Box 616513083-859 CampinasSão PauloBrazil

Quasi-type II heterostructured nanocrystals(NCs)have been of particular interest due to their great potential for controlling the interplay of charge ***,the lack of material choices for quasi-type II NCs restricts the accessible emission wavelength from red to near-infrared(NIR),which hinders their use in light-emitting applications that demand a wide range of visible ***,we demonstrate a new class of quasi-type II nanoemitters formulated in ZnSe/ZnSe_(1-X)Te_(X)/ZnSe seed/spherical quantum well/shell heterostructures(SQWs)whose emission wavelength ranges from blue to *** a given geometry,ZnSe_(1-X)Te_(X) emissive layers grown between the ZnSe seed and the shell layer are strained to fit into the surrounding media,and thus,the lattice mismatch between ZnSe_(1-X)Te_(X) and ZnSe is effectively *** addition,composition of the ZnSe_(1-X)Te_(X) emissive layer and the dimension of the ZnSe shell layer are engineered to tailor the distribution and energy of electron and hole wave *** from the capabilities to tune the charge carriers on demand and to form defectfree heterojunctions,ZnSe/ZnSe_(1-X)Te_(X)/ZnSe/ZnS NCs show near-unity photoluminescence quantum yield(PLQY>90%)in a broad range of emission wavelengths(peak PL from 450nm to 600 nm).Finally,we exemplify dichromatic white NC-based light-emitting diodes(NC-LEDs)employing the mixed layer of blue-and yellow-emitting ZnSe/ZnSe_(1-X)TeX/ZnSe/ZnS SQW NCs.

关键词： ZnSe/ZnS quantum Push

Analysis of structural distortion in Eshelby twisted InP nanowires by scanning precession electron diffraction

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Nano Research 2019年第4期12卷 939-946页

作者： Daniel Ugarte Luiz H. G. Tizei Monica A. Cotta Caterina Ducati Paul A. Midgley Alexander S. Eggeman instituto de Ftsica "gleb wataghin" Universidade Estadual de Campinas-UNICAMP CEP 13083-859 Campinas - SE Brazil department of Materials Science and Metallurgy University of Cambridge Cambridge CB3 OFS UK Laboratoire de Physique des Solides CNRS UMR8502 Univ. Paris Sud 91405 Orsay France School of Materials University of Manchester Manchester M13 9PL UK

Tran smissio n electro n microscopes (TEM) are widely used in nan otech no logy research. However, it is still challe nging to characterize nano scale objects;their small size coupled with dynamical diffraction makes interpret!ng real- or reciprocal-space data difficult. Scanning precession electron diffraction ((S)PED) represents an invaluable contribution, reducing the dynamical contributions to the diffraction pattern at high spatial resolution. Here a detailed analysis of wurtzite InP nanowires (30-40 nm in diameter) containing a screw dislocation and an associated wire lattice torsion is presented. It has been possible to characterize the dislocation with great detail (Burgers and line vector, handedness). Through careful measurement of the strain field and comparison with dynamical electron diffraction simulations, this was found to be compatible with a Burgers vector modulus equal to one hexagonal lattice cell parameter despite the observed crystal rotation rate being larger (ca. 20%) than that predicted by classical elastic theory for the nominal wire diameter. These findings corroborate the importance of the (S)PED technique for characterizing nano scale materials.

关键词： electron microscopy seanning precession electron diffraction Eshelby twist screw dislocation nanowire indium phosphide