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Daniela Cavalcoli

Associate Professor

Department of Physics and Astronomy

Academic discipline: FIS/03 Physics of Matter


Keywords: optoelectronics GaN based heterostructures photovoltaic nanostructures silicon surface photovoltage atomic force microscopy

Study of defects, interfaces, impurities in semiconducting materials.
The physical properties of semiconducting materials are often determined by the characteristics of micro- and nano-structures (crystal defects, impurities, contaminants..). The study of microstructure characteristics is fundamental to understand and predict the physical properties of semiconducting materials and devices. This study is carried out through experimental analyses based on several characterization methods: spectroscopical (junction spectroscopy, non-contact surface photovoltage spectroscopy..) and microscopical (Scanning Electron Microscopy, Scanning Probe Microscopy) methods.
The main objectives of the research are not only the study and characterization of defects in semiconducting materials, but also the development and implementation of non conventional experimental methods for the chacterization of microstructures.
The invesyigated materials are: Si (crystalline, multi and nano-crystalline, amorphous) for microelectronic and photovoltaic applications, CdTe and CdZnTe for applications in detectors, nitride based low dimensional structures.

One example of such studies concerns a functional multiphase material: hydrogenated nanocrystalline Si nc-Si:H. This material is made up by small (5-15 nm diameter) Si nanocrystals embedded in an amorphous Si matrix. It's a very promising material for thin film photovoltaic applications. Quantum confinement effects at Si nanocrystals are responsible for the increase of the energy gap of this material with respect to crystalline Si. Morphological properties of nc-Si:H have been investigated by AFM (Atomic Force Microscopy), electronic properties by conductive- AFM (C-AFM), defect spectroscopy by Surface Photovoltage Spectroscopy (SPS). This material has been studied in the framework of an European Research Project financed within the 6th Framework Programme of EU.

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