Material Physics

AMARAL, Lia Queiroz do
   
We study materials of intermediate degree of organization, using X-ray and other techniques: micellar systems, liquid crystals, membranes, amorphous materials, polymers.

 

ANDREOLI DE OLIVEIRA, Elisabeth

        * surface interactions: interactions of liquid crystals at the boundary surface and how these interactions determine the orientation of such crystals, either in the presence or absence of an external field, are investigated, as well as the influence of the dynamic properties of crystals (reorientation). In this study, boundary surfaces with various characteristics are utilized, for example, polymer or photopolymer coverings that may induce an alignment orientation in the liquid crystal by a process that can be either mechanical (by rubbing the polymer) or by photopolymerization.
        * Study of the properties of multilamellar systems in liquid crystals, composed of lipids and DNA.
The objective of this study is to better understand the process that leads to the positioning of DNA between layers of neutral lipids; without the intermediation of electrostatic interactions.
 For that end we employ techniques of low-angle X-ray reflectivity (which allow determining the microscopic structure) and fluorescence microscopy (for the study of the processes of diffusion of DNA in aqueous layers).
        * Study of the stability of anisotropic colloidal systems:  The use o liquid crystals as a dispersant medium for particles constitutes an anisotropic medium, making it possible to describe the organization of colloidal particles. The stability of those solutions is given by the equilibrium between interactions on the surfaces of the particles and the elasticity of the medium where the liquid crystal orientation ceases being uniform due to the presence of the particles. An interesting aspect of such systems is that the boundary conditions of the particle surfaces can be altered and controlled by the adequate surface treatments. The techniques used are: optics (observation of texture by polarized light microscopy, birefringence measurements), X-ray scattering, scanning differential calorimetry, fluorescence microscopy, and rheology.

 

ASSALI, Lucy Vitoria Credidio

   

Prof. Assali’s group research interests lie in simulation of physical properties of materials performing state of the art calculations of the electronic structure of a wide range of structural and functional materials as well as emerging nanomaterials.
Current research is related to properties of point and complex defects in nitrides, oxides, and semiconducting materials, that are promising for light emitting devices, high power and high frequency electronics, quantum computing, sensors, high-k gate-dielectrics, and understanding the dynamics of the Earth’slower mantle. Understanding the effects of dopants and native point defects is crucial towards their utilization in devices and the properties of the primary constituents of the lower mantle. This field offers exciting opportunities for both fundamental and applied research on several physical aspects.

 

BINDILATTI, Valdir

    Experimental study of critical phenomena and phase transitions in ultra-low temperatures and high magnetic fields. Study of magnetism in diluted systems, particularly in diluted magnetic semiconductors. Development of experimental techniques in ultra-low temperatures and high magnetic field conditions (magnetometry, thermometry).

 

CALDAS, Marília Junqueira

Theoretical study of conventional and/or organic semiconductors, with emphasis on systems of relevance for Si nanotechnology, organic aromatic polymers and hybrid organic/inorganic interfaces. We use many different techniques, for instance empirical force fields for structural properties, and, for electronic structure, from totally empirical methods up to fully ab initio quantum mechanics formalisms within Hartree-Fock or Density Functional theory. When needed, we also move up to Beyond-Mean-Field approaches accounting for electronic correlation effects. At the moment, our main efforts are:
a) For Si nanotechnology, oxidation and functionalization of Si surfaces, and interface formation (Si/SiO2 or Si/organic layers);
b) For organic polymers, we focus on systems of interest to photovoltaics or light emission, including polyphenylene-vinylenes, polythiophenes, polyanilines and others, studying (i) structural properties for amorphous films; (ii) electronic, optical and transport properties for prototypical systems; (iii) polymer/metal and polymer/oxide interfaces.

 

CANUTO, Sylvio Roberto Accioly

      Electronic structure of molecules, biomolecules and clusters. Computational simulation and properties of molecular liquids. Effects of solvents on properties and spectroscopy. Intermolecular forces and hydrogen bonds. Application of Monte Carlo simulation, molecular dynamics and many-body quantum theory. Electric and magnetic properties of molecules and supercritical systems. Development of algorithm techniques.
     Specialized in Many-Body Theory, Computational Simulation and Molecular Modeling, with emphasis on the studies of the effects of solvents in spectroscopy and reactivity of molecules and biomolecules in liquid media, particularly water. Also interested in electric and magnetic properties of molecules and supercritical systems.

 

CHITTA, Valmir Antonio

Physics of new semiconductor materials: Using high magnetic field and low temperature techniques we investigate optical, electrical and magnetic properties of semiconductor heterostructures. The heterostructures are based on group III-V, IV-VI and III-Nitrides semiconductors diluted magnetic semiconductors of these groups, and on semiconductor oxides. The experimental techniques used are: photoluminescence, photoreflectance, Hall effect, magnetoresistance, magnetization and magnetic susceptibility. The main interest is to investigate properties related to the spintronics and nanotechnology development.

 

 

CHUBACI, José Fernando Diniz

Studies of the physical properties of natural and artificial crystals, using optical absorption (UV-VIS-NIR and FT-IR, thermoluminescence (TL), X-ray diffraction (XRD), mass spectroscopy (ICP-MS) and photoluminescence. Interaction of ionizing radiation with matter. Development of new dosimetric materials for thermoluminescence (TL), optically stimulated luminescence (OSL), radiophotoluminescence (RPL) and thermally stimulated exoelectron emission (TSEE).

Formation, modification and characterization of materials by ion beams. Ion implantation for the modification of the properties of ionic crystals and minerals. Formation of thin film by ion beam assisted deposition (IBAD): oxide films with high dielectric constant (AlOx, HfOx, TiOx), semiconductors thin films  (InN), thin films for mechanical applications (TiN, BN, CN) and metallization assisted by ion beams (OLED). Computer simulation of film formation processes and the structure and properties of materials studied.

 

 

CORNEJO, Daniel Reinaldo
Experimental study and computational modeling of low-dimensional nanostructured magnetic systems, such as nanoparticles, nanowires and thin films. Experimental analysis and modeling of mesoscopic phenomena governed mainly by magnetic interactions, such as magnetic hysteresis, exchange-bias, magnetotransport and related phenomena. Experimental analysis and modeling of ferrofluids and liquid crystals doped with magnetic nanoparticles.

 

CRAIEVICH, Aldo Felix

    Nanostructured materials: Structure and mechanisms of transformation. Description:
    Various types of nanostructured materials are studied in solid and liquid states and the structural transformations that occur in the corresponding processes of production. We place a focus, in particular, on structure on a nanometric scale, and on processes of aggregation in liquid colloidal solutions, proteins in solutions, gels, porous xerogels (high-volume and thin films), hybrid nanocomposites and glasses containing quantum dots (semiconducting and metallic nanocrystals). By means of the experimental technique of small-angle X-ray scattering (SAXS), and using X-ray beams produced by synchrotron, the structural transformations are studied in situ to determine related transformation mechanisms.  Characterization of the structure of aggregation mechanisms is made, in  most cases, through the application of concepts of fractal geometry. The SAXS and WAXS (wide angle X-ray scattering) techniques are used together to establish relevant correlations between structures on a nanometric and atomic scale. The above described structural characterizations are employed in order to explain the physicochemical properties of the materials studied.
    Site of the Crystallography Group of the Department of Applied Physics:

    http://web.if.usp.br/cristal/

 

DIAS DA SILVA, Luis Gregório

My research focuses on theoretical and computational studies of electronic correlation effects in nanostructured materials (semiconductor quantum dots, molecular junctions, molecules adsorbed on surfaces, graphene nanoribbons) and, more recently, the study of topological insulators. These materials are ideal for investigating a rich variety of physical phenomena, such as many-body effects (e.g., the Kondo effect), quantum phase transitions,nonequilibrium electronic transport and topological phases of matter.
To this end, I employ state-of-the-art numerical methods for strongly correlated systems, namely the numerical renormalization group (NRG) and the density matrix renormalization group (DMRG), along with their respective time-dependent versions (tNRG and tDMRG).
 
For more information, please visit http://www.fmt.if.usp.br/~luisdias/

 

 

FANTINI, Marcia Carvalho de Abreu

Development of new materials in bulk, thin films and formed by nanoscopic dimensions with morphologic, optical, electric and structural properties that are adjustable for each specific application. The systems are fundamentally investigated using X-ray methods, including diffraction (XRD), scattering (SAXS) and absorption (XANES and EXAFS), employing both conventional X-ray sources and X-ray synchrotron radiation. They are:

1. Organized mesoporous materials prepared with triblock copolymer templates.
2. Polar lipids (monooleines) for controlled release of pharmaceuticals.
3. Nanoceramic materials based on zirconium (ZrO2), used as electrodes and solid electrolytes in solid oxide fuel cells (SOFC).

Visit the group's page: http://web.if.usp.br/cristal

 

FAZZIO, Adalberto

1. Electronic and structural properties of:
 * Nanomaterials
 * Surfaces
 * Surface-adsorbed molecules and atoms
 * Large defects
 * Amorphous oxides

2. Transport properties:
 * Metallic nanowires
 * Carbon nanotubes

3. Density functional theory:
 * Implementation of meta-GGA functionals
 * Excited states

4. Development of algorithms:
 * Monte Carlo method
 * Molecular dynamics

 

FERRAZ, Armando Corbani

    Theoretical studies related to the electronic and structural properties of:
    1. Semiconducting surfaces;
    2. Adsorption of atoms and molecules on surfaces;
    3. Metal-semiconductor surfaces;
    4. Semi-conductive supernetworks;
    5. Processes of diffusion in heterostructures;
    6. Defects and impurities in solids;
    7. Simulation of materials growth processes.
    The development of these studies takes place through first principle calculations, mainly including ab initio pseudopotentials and employing either the static or Hamiltonian procedure (Kohn-Sham method) or the dynamic Lagrangean procedure (Car-Parrinello method).

 

FIGUEIREDO NETO, Antonio Martins

    Investigation of the optical and structural properties of complex fluids using techniques of linear optics (birefringence, optical activity, transmittance) and non-linear optics (Z-scan) and radiocrystallography (X-ray scattering and diffraction). The experimental results are employed in the modeling of these complex fluids.

 

FREITAS, Rafael Sá de

Experimental study of systems of highly correlated electrons in low temperatures and strong magnetic fields, with a focus on the magnetic and electric transport properties of various materials, including transition metal oxides and geometrically frustrated magnetic materials. Besides being highly interesting from the scientific point of view, these materials have a strong technological appeal and, just concerning the industry of magnetic storage technologies, are the source of revenues amounting to thousands of billion dollars per year.

 

GAMMAL, Arnaldo

    My current research involves investigating how Bose-Einstein atomic condensates evolve in time and determining the lowest energy states of the system. Condensates can be considered a laboratory for non-linear physics: with the presence of non-linear diffraction phenomena, collapse, solitons, vortices and shock waves.  Condensates also allow studying condensate matter systems in controlled situations with modifiable parameters. For the study of this time evolution we have developed various computational codes to solve partial differential equations. We are also interested in studies beyond mean field using Monte-Carlo methods and studies of high density vortices.  Additionally, we are also engaged in the studies of decoherence and transition of classic to quantum phase in chaotic systems that may have implications to the studies of coherence of condensates.  More details on http://www.fep.if.usp.br/~gammal

 

GOUSSEV, Guennadii Michailovich

    New materials for spintronic devices.
    We study the basic phenomena of materials and the properties of the structures of Aly Gay-1 As/AlxGax-1 for application in spintronics.  The spin properties in these materials depend strongly on the composition of Al x and y. This opens new possibilities of synthesizing materials with a narrow difference between the spin down energies of two-dimensional electrons in the presence of a magnetic field (low factor-g). This property allows to easily manipulate the electronic spin through the application of an external electric field.   

Transport in nanostructures with strong electron-electron interaction
    We study the transport properties of nanostructures with strong electron-electron interaction. The next generation of semiconducting devices will undoubtedly be based on the rules of quantum mechanics and on researches on very interesting basic physical phenomena such as quantum chaos and electronic correlation. These studies will be consequential for a possible application in devices.
   
Study of nuclear-electron spin interactions in semiconducting systems: Objective: memory devices for spintronics.
    We study nuclear-electron spin interactions in Aly Gay-1 As/AlxGax-1 wide parabolic quantum wells for spintronic applications. In parabolic quantum wells the energy of electrons strongly depends on experimental geometry and could be manipulated through experiments on inclined magnetic fields. This research points in the direction of a new generation of electronic memory devices based on spin.

 

HENRIQUES, André Bohomoletz

    Quantum effects such as superposition and entangling of electronic orbital states and spin are resources with a potential application in the technologies of the future.
Some of the challenges in this area are the optimization of the electronic spin lifetime and of the spin manipulation techniques in very short time scales.
We employ pump-and-probe spectroscopy to investigate magnetic and non-magnetic semiconductor nanostructures. In this technique, lasers with ultra short pulses
(femto or picosecond) are used to manipulate the electron spin. The train of pulses generated by the laser is divided in two (pump and prove). The sample is
perturbed by a pump pulse, and the changes in the sample caused by the perturbation, such as magnetization, reflectivity, absorption and luminescnece, are monitored with
femtosecond resolution. The project involves the development of theoretical models required to interpret the experimental data.

Link: http://siveab-5.if.usp.br/~andreh/pesquisa.html

 

HERNANDEZ, Felix Ghuillermo Gonzalez

    1) Production of semiconducting devices containing quantum dots
    2) Study of electron nanomagnetism and spintronics in nanocrystals
    3) Optical study of the dynamics of electron spin polarization in magnetically doped semiconductors.

 

ITRI, Rosângela

    Study of nanomaterials using scattering techniques (X-ray diffraction, low-angle X-ray and light scattering): micellar systems, crystalline liquids with an emphasis on phase transitions, proteins in solution (effects of additives, temperature and solvents), protein/surfactant/polyelectrolyte/polymer complexes, vesicles and model-membranes (effects of the addition of pharmaceuticals, photoactive molecules, peptides) and magnetic nanoparticles in solution.

 

 

JARDIM, Renato Figueiredo

Interests – Experimental Condensed Matter Physics

1) Synthesis of High TC oxides: study of their structural, magnetic, and transport properties;
2) Studies of inter and intragranular properties of High TC oxides for practical applications;
3) Metal-insulator and superconducting-insulator transitions in Cu and Ni based oxides;
4) Synthesis of magnetic nanoparticles and their general physical properties;
5) Design of supported catalysts on novel nanostructured magnetic materials and their applications in fine chemicals;
6) Novel magnetic and superconducting oxides with unconventional properties.

 

 

MORELHÃO, Sérgio Luiz

        * I. HYBRID RECIPROCAL SPACE. Epitaxy is a process which is fundamental to the technology of semiconductors, enabling the growth of one crystalline lattice upon the other with different lattice parameters. We study the phenomenon of X-ray diffraction of epitaxial films [Journal of Applied Crystallography 40, 546-551 (2007)].
        * II. SYNCHROTRON X-RAY IMAGING. With the dissemination of synchrotron facilities around the world, which started decades ago, the exploration of properties of radiation-matter interaction of hard X-rays for imaging of biological tissues has become a very active research area. In this research we show the relevance of synchrotron X-ray imaging to the study of ophthalmologic diseases, especially to cataract, which is the most common of them [Medical Physics 33, 2338-2343 (2006)], and search for new applications.
        * III. X-RAY PHYSICS IN CRYSTALLOGRAPHY AND NANOTECHNOLOGY. Crystalline materials and nanostructured semiconductive surfaces (quantum dots) are investigated through X-ray multiple diffraction [Physica status solidi A 204, 2548-2554 (2007)].
        * For more details about those research lines, consult the Digital Library of USP
          (http://www.teses.usp.br/teses/disponiveis/livredocencia/43/tde-27082007-...).

 

OLIVEIRA JUNIOR, Nei Fernandes de

    1) Research involving ultra-low temperatures and intense magnetic fields: - investigations on magnetic interactions in diluted magnetic systems; - magnetic phase transitions. 2) Semiconductors: magnetic and transport properties in two-dimensional structures. 3) Detection of gravitational waves: building of a supercooled spherical antenna.

 

PADUAN Filho, Armando

1) Magnetic Phase Trsnsitions
2) Research in High Magnetic Field and Low Temperatures
3) Bose-Einstein Condensation of Magnons

 

PARTITI, Carmen Silvia de Moya

Current research topics are:
1) Natural samples characterization (soils, sediments, rocks) aiming at correlating their magnetic properties with environmental parameters (environmental magnetism);
2) Nanosized iron oxides of interest in ferrofluid research;
3) Characterization of iron phosphate glasses
4) Characterization of lunar soils simulant.

 

PETRILLI, Helena Maria

    Density Functional theory for the description of stationary state properties of various types of materials. Study of electronic and structural properties of biomolecular systems and materials of technological interest, and also of basic physics problems. At the moment, I am collaborating with researchers in Brazil and abroad (http://nanomol.if.usp.br). I am particularly interested in the following problems:
    a) Study of proteins that have potential for application in biomolecular nanoelectronic devices;
    b) Investigation of metal compounds and macrocyclic compounds, especially Crown thioethers.  These are crown-shaped compounds that hold the capacity of encapsulating specific atoms (such as metals), presenting a key-keyhole behavior; we also investigate the possibility of application of these compounds by the pharmaceutical industry.
    c) Study of Fe-Al alloys with the addition of a third element (Mo, initially) to improve mechanical properties. We build phase diagrams (concentration versus temperature) through the combination of electronic structure calculations (quantum mechanics) and methods of statistical mechanics. We also study the electronic and magnetic properties of these alloys.
    d) A class of problems related to the field of optoelectronic devices, which is the investigation of structural properties of conjugated polymers of technological interest, PPP, in particular.
    e) Study of interfaces between polymers (or other sulphur-containing molecules) and transition metal oxides for application in the field of electronic devices.
    f) Study of intermetallic alloys and compounds. As a basic research, we explore the great variety of compounds that crystallize in the same structure with different elements, we aim at helping in the interpretation of experimental techniques that involve hyperfine interactions.
    g) A class of problems in the field of magnetism (basic physics), but with important implications for the magnetic recording industry, the study of magnetic grains of transition metals in metallic matrices, in which we investigate local magnetic properties.

 

PONTUSCHKA, Walter Maigon

    Study of structural, optical and electronic properties of special glasses and amorphous semiconductors.  The characterization of microscopic structural and superstructural unities is mainly based in parallel studies of isomorphic crystalline solids, although some specific phenomena are exclusive to non-crystalline systems.

    Charge and energy transfer in glasses doped with transition elements and rare earths.  EPR, optical and fluorescence studies with the determination of Judd-Ofelt parameters, as well as the investigations of Fano antiresonance, have allowed to demonstrate the charge and energy transfer among ions in co-doped glasses.

    EPR of impurities and defects induced by ionizing radiation in glasses. Studies of growth kinetics and thermal decay of paramagnetic centers have allowed to identify the phenomena of charge carrier trapping and recombination which gave support to later investigations on thermoluminescence, fluorescence, and detailed exploration of the dielectric properties of glasses.

    Optical absorption spectroscopy, Raman and Mössbauer spectroscopy, fluorescence, and thermoluminescence in oxide glasses. Data from previous EPR studies have provided a detailed description of the interactions among ions that structure and the ones that modify the amorphous network.

    Dielectric properties of oxide glasses, absorption and dispersion of microwaves. Studies on the contribution of irradiation-induced electric dipoles for the dielectric constant of glasses, using the technique of impedanciometry for frequencies from 0 to 1 MHz and microwave techniques in the X band (~9 GHz).

    Ferromagnetic resonance of biocompatible superparamagnetic nanoparticles used as magnetic tracers in studies of their distribution and elimination in biological systems and in magnetic resonance imaging.

    Non-linear optical properties of tellurite glasses. Application of heat treatment techniques with the use of electrical poling to induce anisotropy in tellurite glasses with the objective of triggering second harmonic generation. Studies of third-order nonlinearity are also being carried out.

 

QUIVY, Alain André

    Since 1995, I have been responsible for the production of samples of III-V compound semiconductors produced via molecular beam epitaxy (MBE) from the Laboratory of New Semiconducting Materials (LNMS). Besides providing samples to the Brazilian scientific community (and some foreign researches),  I carry out some research lines of my own, connected to the doctoral theses under development in the group, which are related to the study of segregation of indium atoms in the alloy InGaAs, the growth of self-assembled InAs quantum dots and the development of  doped heterostructures specifically for application in micro and optoelectronic devices, such as high electron mobility transistors, light emitting diodes, and semiconductor lasers. We employ various characterization techniques, the most important of which are photoluminescence (PL), atomic force and transmission electric microscopy (AFM and TEM), X-ray diffraction and transport measurements (by Hall effect and Shubnikov-de Haas), to obtain complementary information on  optical, structural and electrical properties of samples. We have recently been able to produce InAs quantum dots, by emitting at the wavelengths of 1.3 and 1.5?m, corresponding to the two main minimums of the absorption spectrum of the optic fibers currently produced [APL 82, 2646 (2003)] and we have formulated a new technique to quantitatively determine, in situ and in real time, the segregation coefficient of indium atoms in InGaAs alloys [APL 81, 2863 (2002)].

 

RABBANI, Said R.

Development of new techniques (pulse sequences and instrumentation) for obtention of image treatment by Nuclear Magnetic Resonance (NMR). Implementation, development and treatment of data via functional images by MR. New application of NMR imaging techniques for determination of other physical properties. In vivo 31P spectrometry.
Application of in vivo high-resolution NMR methodologies for the study of metabolic changes in biological materials, using metabonomic procedures.

 

SANTOS, Antonio Domingues dos

My research activities are in the nanoscience and nanotechnology areas. The main objective is the development of new methods for the production and the characterization of magnetic materials on the micro and nanoscopic scales. Recent work includes:
1)    Production by gas aggregation method and structural/magnetic characterization of magnetic and noble metals nanoparticles.
2)    Experimental micromagnetic studies on magnetic microscopic objects by optical near-field magneto-optical methods.
3)    Study of the interaction between surface plasmons and magnetism.

 

SILVA, Euzi C. Fernandes da

Research in the area of semiconductor materials with emphasis in the development of solid state devices (photodetectors and lasers) based on the III-V compounds operating in the infrared spectral region. The experimental characterization of the devices is performed with electrical measurements (dark current and photocurrent), transport measurements (Hall and Shubnilov-deHaas) and optical spectroscopy (FTIR, photoluminescence (PL) and photoluminescence-excitation (PLE)).

 

 

SANTOS, Maria Cristina dos

     Electronic structure of carbon systems (conjugated organic molecules, fullerenes, carbon nanotubes, graphene planes):  study of conformation, optical properties, molecular magnetism, transport properties, using semi-empirical and ab initio techniques.
Development of hybrid techniques (classic dynamics/quantum mechanics) for the obtention of fluorescence spectra of organic systems.
Structural studies of carbon nanotubes in liquid media involving surfactants and polymers through classical molecular dynamics. 

 

SHIBLI, Suhaila Maluf

    Interferometry of liquid crystals and photothermal and photoacoustic measurements of various materials.
    http://axpfepl.if.usp.br/~gfcxhp

 

SILVA, Antônio José Roque da

    Study of the electronic structure and dynamic properties of solids, atomic and molecular systems. The main interest is in the area of computational simulations, with strong emphasis on the utilization of first principle methods based on Density Functional theory for describing the electronic structure of materials, as well as in simulations of finite temperature, using either Molecular Dynamics or Monte Carlo. Properties of nanostructures have been the focus of research. Some examples are: carbon nanotubes, metallic nanowires, semiconductor nanowires, molecular devices and fullerenes. Special attention has been devoted to the investigation of transport properties and to how they are affected by impurities and defects.

 

SILVA, Euzi C. Fernandes da

Research in the area of semiconductor materials with emphasis in the development of solid state devices (photodetectors and lasers) based on the III-V compounds operating in the infrared spectral region. The experimental characterization of the devices is performed with electrical measurements (dark current and photocurrent), transport measurements (Hall and Shubnilov-deHaas) and optical spectroscopy (FTIR, photoluminescence (PL) and photoluminescence-excitation (PLE)).