Nanostructured multifunctional materials and nanocomposites
Institut za Fiziku
Center for Solid State Physics and New Materials
National Research Project
This project consists of several topics: 1. Photoluminescence and Raman spectroscopy of semiconducting nanostructures, 2. Transport properties of materials with colossal magnetoresistance effect, 3. Investigations of new superconductors in Mg-B and Cu-Pb-Ag-O systems, 4. Vibrational and magnetic properties of low-dimensional magnetic structures in spin-ladder vanadates, 5. Vibrational properties of nanotubes, small fullerens and anilin based oligomers and polymers, 6. Properties of nanocomposites obtained by sol-gel technology, 7. Quantum-mechanical engineering of semiconducting quantum structures and 8. Properties of materials under high pressure.
The investigation of single quantum dots by low-temperature micro-photoluminescence and micro-Raman is proposed, allowing direct observation of ultra narrow photoluminescence from delta-function energy levels within the dots. Low-temperature micro-Raman and micro-photoluminescence measurements will be used to investigate porous-Si made by photochemical etching of bulk material.
We will use optical methods and transport properties measurements to analyze how structural disorder influences the electronic properties of mixed valence manganites. Two different types of disorder has been considered: 1. cationic vacancies at B(Mn) sites, in the series of compounds La1-xAxMnO3+d (A=Na, K), 2. A-cations with different ionic radii in the series of compounds La0.85(Na1-xKx)0.15MnO3.
We will investigate transport and optical properties of the new high-temperature superconductor, MgB2 and search for the relevant high-temperature phase of Cu-Pb-Ag-O systems, that promises the room temperature superconductivity.
One of the central issues in the physics of strongly correlated electron systems is study of low dimensional magnetic properties. These properties, like for example the ground state energy and excitation spectra, are dominated by strong quantum fluctuation, pronounced spin-spin correlations and a suppression of the long-range magnetic order. The main goal of the present project is to identify the spin-gap related modes and relevant exchange integrals (magnetic crystal structure).in the Raman spectra of spin-ladder materials (Sr-Cu-O cuprates and AV2O5 vanadates, A=Na, Li, Cs, Ca, Mg),
Vibrational properties of nanotubes, fulerenes smaller than C60 and conducting polymers will be calculated using a model based on adiabatic harmonic approximation and valence-optical theory.
Synthesis of thin and thick films and nanocomposites in mesoporous silica-gels will be the main goal of this activity. Obtained materials will be characterized by measuring of their mechanical (density, porosity, specific surface) and optical (vibrational spectroscopies) properties.
This activity includes development of more sophistical models for semiconducting devices, such as lasers, detectors and modulators, based on intraband electronic transitions.
Optical properties of molecular crystals, such as SnGeS3, AV2O5, will be investigated at high hydrostatic pressures. We will search for phase transitions and pressure induced change of phonon dynamics in these materials.