The main fields of investigation and specializations are reported in the following.
SEMICONDUCTOR LOW-DIMENSIONAL NANOSTRUCTURES
The research on "Preparation and characterization of nanostructures for photonics" takes advantage of an integrated package of expertises on preparation, modelling and study of physical properties of low-dimensional structures based on III V semiconductors; such expertises have been developed in more than 20 years of activity in the field; they deal with:
o Molecular Beam Epitaxy (MBE) growth of zero-dimensional (self-assembled quantum dots) and two-dimensional (e.g. quantum wells and superlattices) structures based on III-V semiconductors;
o Design and modelling of quantum dot nanostructures for photonic applications;
o Study and characterization of morphological and structural properties by means of:
o Atomic Force Microscopy (AFM);
o Transmission Electron Microscopy (TEM);
o Advanced X-ray diffraction techniques and X-ray topography;
o Study and characterization of electrical properties of low-dimensional and three-dimensional systems by:
o Space-charge techniques (Capacitance-Voltage (CV), Deep Level Transient Spectroscopy (DLTS) and variants, Admittance, Electrochemical Profiling);
o Current-Voltage (IV) and Hall effect measurements;
o Optical lithography and metallizations for the preparation of test devices
o Study and characterization of optical properties of low-dimensional nanostructures by using:
o CW variable-temperature photoluminescence.
One-dimensional photonic crystals based on III-V semiconductors are designed, prepared by MBE and characterized by optical reflectance and X-ray diffraction techniques.
The Magnetic Materials group has developed a pluriannual expertise in hard magnetic materials.The research has been devoted to the preparation and characterization of a large number of alloys (RE-TM, oxides, Heusler), to the modelling of magnetization processes (e.g. FOMP theory), and to the development of new measurement techniques (e.g. SPD technique for the anisotropy determination in polycrystalline materials).
At present, the research interests are focused on:
- magnetic thin films, exchange-spring magnets, and nanostructures for applications in recording media, and micro/nano-electromechanical systems
- intermetallic ferromagnetic-shape-memory materials, magnetocaloric materials, and hard magnetic materials for applications as sensors/actuators, eco-compatible refrigerants and permanent magnets
- magnetic oxides for application in spintronic devices
- metallic oxide nanowires for sensor applications
- ferroelectrics thin films for non volatile memories and sensors
- high Tc superconductors: materials developments, crystal growth, phase diagram, long length YBCO Coated Conductors for power applications
MATERIALS FOR PHOTOVOLTAIC APPLICATIONS
Based on the very positive results of the European Project "THE REV" (A Thermophotovoltaic generator for hybrid electric vehicles), a series of successful projects were initiated by the former partners of that project. The Institute is involved in some of these initiatives as an "R&D provider" as defined by the European Commission. In particular:
- Characterisation of alpha and beta-prototypes of III-V concentrator solar cells for QuantaSol Ltd., a spin-out company launched by Imperial College London in 2006. Later in 2008 this project, fully funded by QuantaSol, will be expanded to include some "blue sky" research on novel structures and devices to be prepared and tested at the CNR in Parma.
- Design and development of a secondary concentrator for a novel building-integrated photovoltaic module developed by the UK company, SolarStructure Ltd. This activity is part of a larger project involving two large multinationals of the building industry, an Italian curtain wall manufacturer and a Dutch company operating in the solar blind sector. Engineering and prototyping of the secondary concentrator, a key component of SolarStructure's IP, will be part of joint project with a Bonomi srl, a plastic-materials company based in Parma.
- Development of selective emitters and advanced optical filters for thermophotovoltaic extension-units designed to be fitted in domestic heating systems. The project is led by Baltur srl. a local SME manufacturing high performance burners and boilers sector and is structured in three stages: a) proof of concept, b) prototype fabrication, c) commercialisation plan. The University of Ferrara and Salentec srl. are the other two partners of the project. This project is also part of a wider PRIN application which is still awaiting response from the Ministry of Research.
In addition to these commercially-driven activities, the Institute will also carry out explorative research in the field of hybrid photovoltaic-photocatalytic systems for co-generation of electricity and hydrogen. An international FIRB application for a joint Chinese-Italian project on this topic was submitted in November 2007 and a new application for the European programme IDEAS is being prepared.
Recently, a project called "PED4PV" on photovoltaic application has been approved and financed; it deals with the development of an innovative solar cell, based on the deposition of successive layers (absorber and TCO) by PED (Pulsed Electron Deposition), developded at IMEM. The partners of the project, funded by the Italian Government (programme: Industria 2015) and characterized by a strong industrial participation, are CTG (Italcementi Group), Marazzi, X-Group, Rial Vacuum, Salentec and IMEM-CNR.
IMEM has a long-standing tradition in the development and the study of novel materials with appropriate functionalities for advanced applications. On the basis of the previous expertises, the available know-how and the demand of the up-dated devices, the materials research is mainly focused on:
- nanostructured hybrid organic inorganic materials
- new inorganic materials with novel electronic properties (manganites, cuprates, superconductors, multiferroics)
- metastable phases stabilized through chemical substituents.
- Growth of metallic thin films
- Thermally induced disorder study on metallic surfaces
- Growth and characterization of organic molecular monolayers
- Gas/surface interaction study, chemiabsorption
MATERIALS PREPARATION AND CRYSTAL GROWTH
IMEM (former MASPEC) is one the main Institutes of CNR established to develop researches on new materials and materials preparation technologies. These aspects traditionally represent the object of the IMEM activities and they were pursued by developing suitable know-how and the relevant facilities, which include:
o Single crystals:
Czochralski, Bridgman, Hydrothermal
Chemical vapour transport, Sublimation Flux, growth from solution
o Thin Films:
o Growth by Metal Organic Vapor Phase (MOCVD) technique of semiconducting materials epitaxial films:
LPE, Laser ablation, r.f. sputtering, thermal co-evaporation, e-beam induced evaporation, PED
Single source thermal ablation and spin coating of organic-inorganic hybrids
o Polycrystal and alloys:
Ceramic, sol-gel, co-precipitation,
Melt-spinning arc and induction-melting processes
o Inorganic synthesis:
low/medium pressure, sintering
High pressure (multi-anvil, piston-cylinder)
IMEM is fully equipped for the characterization of the new materials, mainly dealing with structural, electrical, magnetic, optical, and thermodynamic properties. A list of the main facilities and the relevant know-how follows:
High resolution x-ray diffraction and topography for epitaxial samples and crystalline materials
X-ray diffraction and topography, X-ray and neutron diffraction data refinements
Electron microscopy: SEM (EBIC, TCL), TEM and microanalysis
Scanning probe techniques
Scanning Capacitance, Torsional Resonance Mode, Scanning Tunnel, Atomic Force, and Magnetic Force Microscopy
Nanolithography and Nanomanipulation
Preferential chemical etching
Hall effect, DLTS, C-V, admittance spectroscopy,
Thermally stimulated capacitance, transport and resistivity measurements
thermally stimulated current, impedance spectroscopy, electrochemical C-V profiling
Magnetotransport (AC/DC) and capacitive (AC) measurements in magnetic field (up to 5.5.T)
IR spectroscopy, photoluminescence, Kerr effect
VSM, AGFM, and SQUID magnetometry, anisotropy measurement (SPD technique) in pulsed magnetic fields, transverse susceptibility, thermomagnetic analysis
DTA, spectrophotometry (VIS, UV, AAS), electrochemical techniques, microanalysis
Several modelling expertises are present, which mainly focus on:
- Theoretical study and simulations via first principles and classical methods of the electronic and structural properties of surfaces, interfaces, and nanostructures
- Interchangable stochastic and markovian processes
- Transport properties in nanowire and quantum dots
- Monte Carlo simulation of bidimensional spin models for the description of ultrathin films
- Modelling of magnetism in multisulattices systems
- Theoretical studies on the superconductivity in MgB2 and on the coexistence of superconductivity and antiferromagnetism in heavy fermions systems.
Realization of measuring techniques and innovative instruments, realization of x-ray optics for x-ray instrumentation, electron gun and thermal metalizations reactive ion etching, photolitography, wire bonding, sample polishing, heat treatments in inert atmosphere.