Work function of MgO single crystals from ion-induced secondary electron emission coefficient
ABSTRACT The work functions ϕω of MgO single crystals with its respective orientation (111), (200), and (220) have been investigated from their ion-induced secondary electron emission coefficient Γ, respectively, using various ions with different ionization energies in a Γ-focused ion beam system. The work function ϕω for MgO single crystal with (111) orientation has the lowest value, 4.22 eV, whereas it is 4.94 eV for (200) and the highest value is 5.07 eV for (220). These work functions of MgO single crystals can explain the nonzero values of the ion-induced secondary electron emission coefficient Γ for Xe+ ions, whose ionization energy is 12.13 eV.
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ABSTRACT: Stable and efficient organic solar cells with Mg (20 at. %): Ag alloy cathodes and bulk-heterojunction absorber layers from metal (e.g., Cu, Zn)-phthalocyanine and C60 small molecules are demonstrated. Device efficiencies of 4.0% under an illumination of 100 mW/cm2 at 25̊C were achieved as a result of the fine adjustment of the cathode work function as well as of the absorber design. By combining low and high work function materials, the work function in both Mg/Ag bilayer and Mg:Ag alloy layer cathodes was adjusted for optimum photovoltaic parameters. The electric and photovoltaic properties of the devices are discussed with respect to the cathode layer structure. The formation of the absorber/cathode interface was investigated by x-ray photoelectron spectroscopy measurements (XPS). The work function of the absorber and cathode layers were determined from the XPS high binding energy cutoff (HBEC) spectra. For optimized devices, the work function of the cathode at the side adjacent to the absorber layer equals 4.0…4.1 eV. While devices with Mg/Ag bilayer contacts exhibit a 65% efficiency drop in the first month after the preparation, devices with Mg:Ag alloy contacts demonstrate stable photovoltaic parameters within the time of the study of ∼ 1 year.Energy Procedia 01/2012; 31:96–101. DOI:10.1016/j.egypro.2012.11.170
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ABSTRACT: This paper proposes a modified alternating current plasma display panel (PDP) in which gold nanoparticles are incorporated into a bare MgO layer to enhance the performance of the protective layer. The proposed structure's ion-induced secondary electron yield, which is expressed in a gamma value ( value) is greater than that of a bare MgO layer; as a result, the operating voltage decreases by 10 V to 20 V. The integration of emitted infrared (IR) light and the power density consumed by the discharge current are both increased, but the ratio of increment is greater for the case of the IR light. Consequently, IR efficacy is increased. The IR response time of the sustain discharge and the address discharge time lag are reduced by the enhanced wall charge accumulation characteristic and the exoelectron emission property. The results of ultraviolet photoelectron spectroscopy show that a MgO layer with Au nanoparticles has a lower work function than a conventional bare MgO layer. Furthermore, the structure that is not flattened by nanoparticles seems to enhance the secondary electron emission property of the MgO protective layer. Consequently, the value is enhanced by the two reasons previously mentioned.IEEE Transactions on Electron Devices 11/2010; DOI:10.1109/TED.2010.2058850 · 2.36 Impact Factor
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ABSTRACT: Lanthanum hexaboride (LaB6) thin films were used as protective layers in alternating current plasma display panels (AC-PDPs). The firing voltages and discharge delay time of protective LaB6 thin films were evaluated and compared with the conventional protective MgO layers in planar-type test panels filled with 5%–15% Ne-Xe. By employing LaB6 thin films as protective layers, both the firing voltages and discharge delay time decreased drastically. Improvements in the discharge properties of the LaB6 thin film could be attributed to the lower work function, offering more priming electrons during the discharge process.Chinese Science Bulletin 07/2012; 57(20). DOI:10.1007/s11434-012-5221-0 · 1.37 Impact Factor