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Low-emissivity films consisting of a metal oxide/Ag/metal oxide structure improve the thermal insulation performance of windows. Deposition of an oxide layer on top of the Ag layer requires either the insertion of a blocking layer (BL) or the sputtering deposition of an oxide target under an argon atmosphere. In this study, we carried out a sequential sputtering deposition method for inserting a BL to achieve both high visible-light transmittance and low sheet resistance. The effects of metallic and oxide BLs on the sheet resistances were investigated, and metallic BLs were confirmed to cause an increase in sheet resistance due to the diffusion of metal atoms into the Ag layer. Oxide BLs deposited under low oxygen concentrations maintained the low sheet resistance. The most significant result was obtained with a TiO x BL deposited under 2.9% oxygen, which prevented an increase in sheet resistance even after the deposition of the top layer (TL). By optimizing the thickness of the TL, high visible-light transmittance and low sheet resistance were achieved in a glass/TiO2/ZnO/Ag/TiO x /ZnO multilayer. Thus, high-performance multilayers could be fabricated by selecting an appropriate BL, which is beneficial for the industrial fabrication of low-E films.

Silver-based low-emissivity films have been studied to improve window insulation performance. We have reduced the resistivity of Ag in glass/ZnO/Ag structures by inserting a TiO2 in the lowermost layer. In another study, we have also found that the resistivity of Ag thin film can be reduced by changing the sputtering gas from Ar to Kr. In this study, both methods were adapted to achieve even lower resistivity and the factors involved were analyzed in detail. The lowest electrical resistivity achieved was 3.3 μΩ·cm for a combination of a glass/TiO2/ZnO/Ag structure and Kr gas sputtering, which was 2.9% less than that for a glass/TiO2/ZnO/Ag structure with Ar gas sputtering. X-ray diffraction, atomic force microscopy, and secondary ion mass spectroscopy results indicated that the important factor influencing the electrical resistivity was a reduction in the amount of sputtering gas trapped in the Ag layer by depositing the layer using Kr gas.

To improve the thermal insulation performance of windows, lowering the electrical resistivity of the Ag-based multilayer structure in low-emissivity (low-E) glass is necessary. We have reported that the electrical resistivity of the structure can be reduced from 4.4 μΩ·cm to 3.4 μΩ·cm by inserting TiO2 in glass/TiO2/ZnO/Ag deposited by sputtering method. In this study, Nb2O5 and ZrO2 were selected as the lowermost layers and their effects on electrical resistivity were investigated. When the lowermost layer was Nb2O5, the resistivity became 3.4 μΩ·cm; however, the resistivity did not improve when the lowermost layer was ZrO2. Based on the X-ray diffraction, atomic force microscopy, and transmission electron microscopy results, we determined the factors correlated with electrical resistivity and elucidated the suitable conditions of the lowermost layer for reducing the electrical resistivity of the Ag-based multilayer structure in low-E glass.

In order to improve the heat insulating properties of low-emissivity coatings, it is necessary to reduce the electrical resistivity of their multilayer structure, which consists of an Ag layer and oxide layers. In this study, structures comprising glass/ZnO/Ag and glass/TiO2/ZnO/Ag were deposited by sputtering, and the effects of these layers on the electrical resistivity were investigated. For a ZnO layer deposited at low sputtering gas pressure, lower surface roughness reduced the electrical resistivity of the Ag layer. Also, it was found that the electrical resistivity could be further decreased by inserting a TiO2 lowermost layer between the substrate and the ZnO layer. The results of X-ray diffraction and X-ray reflectivity measurements showed that the decrease in resistivity was mainly due to the improved crystal orientation of the ZnO and Ag layers.

We investigate the electron-spin injection dynamics via tunneling from an In0.1Ga0.9As quantum well (QW) to In0.5Ga0.5As quantum dots (QDs) in coupled QW-QDs nanostructures. These coupled nanostructures demonstrate ultrafast (5 to 20 ps) spin injection into the QDs. The degree of spin polarization up to 45% is obtained in the QDs after the injection, essentially depending on the injection time. The spin injection and conservation are enhanced with thinner barriers due to the stronger electronic coupling between the QW and QDs. (C) 2014 AIP Publishing LLC.

We report the temperature dependence of the dynamics of optical spin injection from GaAs barriers into self-assembled quantum dots (QDs) of In0.5Ga0.5As. Transient circular-polarization properties of photoluminescence (PL) from excited states in QDs depend strongly on the temperature (T) and rate-equation analysis shows the T-dependent dynamics of spin injection. The filling for the majority spin states is strongly suppressed as T increases above 100 K, enhancing the circular polarization degree of PL. This suppression originates from thermal redistribution of electrons from the excited states in the QDs to the barrier. In contrast, spin relaxation during the injection becomes significant at T ≥ 150 K.