In this study, double layer KTN/STO thin films were fabricated on Pt/Ti/SiO₂/Si substrate, their structural and electrical properties were measured according with the number of STO coatings, and their applicability to microwave materials was investigated. The average grain size was about 80~90 nm, the average thickness of the 6-coated KTN thin film was about 320 nm, and the average thickness of the STO thin film coated once was about 45~50 nm. The dielectric constant decreased with increasing frequency, and as the number of STO coatings increased, the rate of change of the dielectric constant with the applied electric field decreased. The tunability of the KTN thin film showed a maximum value of 19.8% at 3 V. The figure of merit of the KTN/1STO thin film was 9.8 at 3 V.

Electric double layer capacitors (EDLCs) are promising candidates for energy storage devices in electronic applications. An EDLC yields high power density but has low specific capacitance. Carbon material is used in EDLCs owing to its large specific surface area, large pore volume, and good mechanical stability. Consequently, the use of carbon materials for EDLC electrodes has attracted considerable research interest. In this paper, in order to evaluate the electrochemical performance, graphene is used as an EDLC electrode with flake sizes of 3, 12, and 60 nm. The surface characteristic and electrochemical properties of graphene were investigated using SEM, BET, and cyclic voltammetry. The specific capacitance of the graphene based EDLC was measured in a 1 M TEABF₄/ACN electrolyte at the scan rates of 2, 10, and 50 mV/s. The 3 nm graphene electrode had the highest specific capacitance (68.9 F/g) compared to other samples. This result was attributed to graphene’s large surface area and meso-pore volume. Therefore, large surface area and meso-pore volume effectively enhances the specific capacitance of EDLCs.

Coil specimen was prepared by coating a copper wire with two varnish thin layers: the first was polyamideimide (PAI)/nanosilica (5 wt%) varnish and the second was anti-corona PAI/nanosilica (15 wt%) varnish. Insulation breakdown voltage was investigated under inverter surge condition at 20℃, 70℃, 100℃, 150℃, 200℃, 250℃, respectively. The insulation lifetime of the two layered coil was tens of times longer than that of original PAI coil. And the insulation lifetime decreased with increasing ambient temperature because there was weak binding strength between copper and varnish layer.

The photoinduced hydrophilicity of TiO2/WO3 double layer films was fabricated by using a conventional rf-magnetron sputtering method. The photoinduced hydrophilic reaction of the TiO2 surface was enhanced by the presence of WO3 under the TiO2 layer by irradiation of a 10 W cylindrical fluorescent light bulb. However, when the TiO2 and WO3 layers were separated by an insulating layer, the surface did not appeared high hydrophilic,under the same light bulb. The enhanced photoinduced hydrophilic reaction can be explained by the charge transfer between TiO2 and WO3 layers. It was also demonstrated that visible light passing through the TiO2 layer could excite WO3. Thus, visible light can be used for the hydrophilic reaction in the present TiO2/WO3 system.

Crystalline silicon solar cells with SiNx/SiNx and SiNx/SiOx double layer anti-reflection coatings(ARC) were studied in this paper. Optimizing passivation effect and optical properties of SiNx and SiOx layer deposited by PECVD was performed prior to double layer application. When the refractive index (n) of silicon nitride was varied in range of 1.9∼2.3, silicon wafer deposited with silicon nitride layer of 80 nm thickness and n= 2.2 showed the effective lifetime of 1,370 ㎛. Silicon nitride with n= 1.9 had the smallest extinction coefficient among these conditions. Silicon oxide layer with 110 nm thickness and n= 1.46 showed the extinction coefficient spectrum near to zero in the 300∼1,100 nm region, similar to silicon nitride with n= 1.9. Thus silicon nitride with n= 1.9 and silicon oxide with n= 1.46 would be proper as the upper ARC layer with low extinction coefficient, and silicon nitride with n=2.2 as the lower layer with good passivation effect. As a result, the double layer AR coated silicon wafer showed lower surface reflection and so more light absorption, compared with SiNx single layer. With the completed solar cell with SiNx/SiNx of n= 2.2/1.9 and SiNx/SiOx of n= 2.2/1.46, the electrical characteristics was improved as ΔVoc= 3.7 mV, ΔJsc= 0.11 mA/cm2 and Δ Voc= 5.2 mV, ΔJsc= 0.23 mA/cm2, respectively. It led to the efficiency improvement as 0.1% and 0.23%.