Seminarium Fizyki Ciała Stałego

Ultra-thin layers of wide-gap oxides (so-called "high-k oxides") deposited by the Atomic Layer Deposition (ALD method) are currently used in electronics, as gate oxides and elements of the new generation of semiconductor memories, in photovoltaics, as barrier layers or as anti-reflective layers, and in opto-electronics, in thin films electroluminescence devices or as anti-reflective coatings.During the seminar I will discuss the advantages of the ALD deposition method, and then the fascinating properties of so-called high-k oxides. Thin layers of high-k oxides are deposited using the ALD at low-temperature and the process is optimized to ensure their best stoichiometry. Unfortunately, in the following annealing processes of electronic structures, defects resulting from deviations from the ideal stoichiometry can be generated - such as oxygen vacancies or broken bonds. In some extreme cases the concentration of these defects can be high, which can generate significant ionic conductivity associated with the diffusion of oxygen ions. In the case of hetero-structures, the properties of oxides determine the accumulation of charges in the near-surface layer of the semiconductor. The generation of defects at the dielectric/semiconductor interface (and within the insulating layer) limits the efficiency and reliability of electronic components, by increasing the leakage current and reducing the mobility of carriers in the semiconductor. Thus, it is necessary to ensure a low concentration of defects at the interface. I will discuss selection of oxides for a given application and still many open questions regarding their properties.