We evaluated the structural, electrical and optical properties of tungsten (W)-doped Ge₈Sb₂Te₁₁ thin films. In a previous work, GeSbTe alloys were doped with different materials in an attempt to improve thermal stability. 200 mm thick Ge₈Sb₂Te₁₁ and W-doped Ge₈Sb₂Te₁₁ films were deposited on p-type Si (100) and glass substrates using a magnetron co-sputtering system at room temperature. The fabricated films were annealed in a furnace in the 0~400℃ temperature range. The structural properties were analyzed using X-ray diffraction (X`pert PRO, Phillips). The results showed increased crystallization temperature (T_c) leading to thermal stability in the amorphous state. The optical properties were analyzed using an UV-Vis-IR spectrophotometer (Shimadzu, U-3501, range : 300~3,000 nm). The results showed an increase in the crystalline material optical energy band gap (E_op) and an increase in the Eop difference (△E_op). This is a good effect to reduce memory device noise. The electrical properties were analyzed using a 4-point probe (CNT-series). This showed increased sheet resistance (R_s), which reduces programming current in the memory device.

Tungsten carbide (WC) has been suggested as a new buffer layer for the GaN-on-Si technology. We have investigated and optimized the sputtering condition of WC layer on the Si-substrate. We confirmed the suppression of the Si melt-back phenomenon. In addition, surface energy of WC/Si layer was measured to confirm the possibility as a buffer layer for GaN growth. We found that the surface energy(γ=82.46 mJ/cm²) of WC layer is very similar to that of sapphire substrate(γ=82.71 mJ/cm²). We grow GaN layer on the WC buffer by using gas-source MBE, and confirm that it is available to grow a single crystalline GaN layer.

Thin films of cubic Na0.6WO3, which is one of the sodium tungsten bronze, were fabricated byrf sputtering for the electrode applications in integrated sensors and actuators. A single-phase cubicNa0.6WO3 sputtering target of power type was prepared by conventional solid-state reaction. Thin filmswere deposited from the powder target, and the as-deposited films were amorphous, thus they annealedby tube furnace or RTP for crystallization. Thin films having cubic phase NaxWO3 were fabricated by theoptimization of sputtering and post-annealing conditions, but single-phase cubic Na0.6WO3 thin films werenot obtained. Although the films were not in single phase, they had good electrical conduction propertiesshowing electrical resistivities of 10-4 Ω·cm order.

The powders for the NaxWO3 (x= 1 and 0.75) sputtering targets were synthesized by the calcination in reductive atmosphere. Near single-phase NaWO3 and single-phase Na0.75WO3 powder targets were prepared. By using the targets, thin films of each composition were deposited by rf magnetron sputtering on the SiO2 (100 nm)/Si substrates and annealed by RTP (rapid thermal processing) for crystallization. In the case of the NaWO3 composition, single-phase NaxWO3 thin films, where x was believed to be slightly less than 1, were fabricated accompanying the Na-diffusion into the substrates during RTP. However, in the case of the Na0.75WO3 thin film preparation, it was unable to make single-phase thin films. From the phase formation behaviors of both powders and thin films, it was revealed that NaxWO3 with nonstoichiometric composition of x, which was slightly less than 1, was favorable. The good electrical conduction properties were obtained from the single-phase NaxWO3 thin films. Their electrical resistivities were as low as 7.5 × 10-4 Ω·cm.

An optical lens is usually produced in the manner of high temperature compression molding with tungsten carbide alloy molding cores, it is necessary to develop and study technology for super-precision processing of molding cores and coating the core surface. As main methods used in surface improvement technologies using thin film, DLC present high hardness, chemical stability, and outstanding durability of abrasion to be extensively applied in various industrial fields. In this study, the effect of DLC coating of a thin film by means of the FVAS (filtered vacuum arc source) analyzed the characteristics of thin film. Surface roughness before and after DLC coating was measured and the result showed that the surface roughness was improved after coating as compared to before coating. In conclusion, it was observed that DLC coating of the ultra hard alloy core surface for molding had an effect on improving the surface roughness and shape of the core surface. It is considered that this will have an effect on improving abrasion resistance and the service life of the core surface.

Rhenium-Iridium(Re-Ir) thin films were deposited onto the tungsten carbide(WC) molding core by sputtering system. The Re-Ir films were prepared by multi-target sputtering with iridium, rhenium and chromium as the sources. Argon and nitrogen were inlet into the chamber to be the plasma and reactive gases. The Re-Ir thin films were prepared with targets having atomic percent of 3:7 and the Re-Ir thin films were formed with 240 nm thickness. The Re-Ir thin films on tungsten carbide molding core were analyzed by scanning electron microscope(SEM) and surface roughness. Also, adhesion strength and coefficient friction of Re-Ir thin film were examined. The Re-Ir coating technique has been intensive efforts in the field of coating process because the coating technique and process have been their feature, like hardness, high elasticity, abrasion resistance and mechanical stability and also have been applied widely the industrial and biomedical areas. In this report, tungsten carbide(WC) molding core was manufactures using high performance precision machining and the efforts of Re-Ir coating on the surface roughness.