Crystal orientation of epitaxial film deposited on silicon surface.

Direct growth of oxide film on silicon is usually prevented by extensive diffusion or chemical reaction between silicon (Si) and oxide materials. Thermodynamic stability of binary oxides is comprehensively investigated on Si substrates and shows possibility of chemical reaction of oxide materials on Si surface. However, the thermodynamic stability does not include any crystallographic factors, which is required for epitaxial growth. Adsorption energy evaluated by total energy estimated with the density functional theory predicted the orientation of epitaxial film growth on Si surface. For lower computing cost, the adsorption energy was estimated without any structural optimization (simple total of energy method). Although the adsorption energies were different on simple ToE method, the crystal orientation of epitaxial growth showed the same direction with/without the structural optimization. The results were agreed with previous simulations including structural optimization. Magnesium oxide (MgO), as example of epitaxial film, was experimentally deposited on Si substrates and compared with the results from the adsorption evaluation. X-ray diffraction showed cubic on cubic growth [MgO(100)//Si(100) and MgO(001)//Si(001)] which agreed with the results of the adsorption energy.

Complex Impedance Analyses of Li doped ZnO Electrolyte Materials.

The recent studies indicate that internal point defects in solid electrolytes modify the electronic and ionic conductivity and relaxation mechanism of solid oxide fuel cells. We focused on synthesis of Lithium (Li) doped Zn1-xCoxO (x = 0.00, and 0.10) nanoparticles employing chemical synthesis technique with a reflux setup under constant Argon gas flow. The structural characterizations were performed by x-ray powder diffractometer (XRD) and x-ray photoelectron spectroscopy (XPS). Then, Rietveld refinements were performed to investigate the replacement of Li atom amount in ZnO lattice. Moreover, the variations in ionic conduction dependent on 5, 10 and 20 mol% Li doped ZnO were analysed via ac impedance spectroscopy. The complex measurements were performed in an intermediate temperature range from 100 °C to 400 °C. Ac conductivity responses of each sample were disappeared at a certain temperature due to becoming electronic conductive oxides. However, this specific temperature was tuned to high temperature by Li doping amount in ZnO lattice. Furthermore, the activation energy change by Li dopant amount implied the tuneable ionic conduction mechanism.