2024, Vol.34, No.6

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

CaF2 (calcium fluoride) single crystal is in increasing demand as an objective lens for semiconductor lithography equipment with deep ultraviolet (DUV) light source. High crystallinity, excellent and homogeneous optical properties, and low birefringence value are required to be used as a material for UV lens. In this study, <111> CaF2 single crystals were grown via czochralski growing method. Growth direction, single crystallinity, high purity and high optical transmittance of CaF2 crystal were confirmed. In addition, the crystal shows average refractive index of 1.437124, 1.433864, and 1.43248 according to 486.1 nm, 587.6 nm, and 656.3 nm wavelengths, respectively. Calculated uniformity of refractive index was 17.4 ppm, 10.5 ppm, and 10.5 ppm, which shows excellent optical homogeneity. Moreover, residual stress was analyzed through comparing birefringence at 193 nm and 570 nm wavelength. CaF2 single crystal shows average birefringence of 1.021 nm/cm under 193 nm light source, while 0.788 nm/cm at 570 nm source. Considerable changes of birefringence pattern according to light source wavelength were not observed. Conclusively, we confirmed that our as-grown CaF2 single crystal has remarkable optical and structural properties such as uniform refractive index and low birefringence.

The Ti3C2Tx MXene is an emerging material for electrical devices, sensing, energy, environmental, and biomedical applications. Therefore, the effective development of synthesis and functionalization strategy has been triggered from delamination via etching routes to the addition of functional groups. The present report demonstrates the synthesis of Ti3C2Tx and modification by titanium dioxide (TiO2). The incorporation of titanium dioxide (TiO2) showed different morphology, chemical structures, and chemical composition compared to Ti3C2Tx. Moreover, the electrical characteristics have been investigated and showed a promising performance as semiconductor devices. The existence of titanium dioxide turned the Ti3C2Tx IV characteristics from ohmic behavior toward the Schottky behavior, resulting in enhanced hysteresis of memory devices and responsibility of chemical sensors upon NO2 gas.

Tungsten carbide is known for its excellent mechanical properties and is commonly used as a surface coating material for various tools. However, existing coating technologies are hindered by high process costs and poor durability due to the thinness of the coating layers. Therefore, there is a need to reduce costs and develop a unified manufacturing process. In this study, we explore a technique for analyzing and manufacturing tungsten carbide coating samples using a single sintering process with tungsten carbide and stainless steel powder. When these powders are sequentially filled and sintered in a mold, pore regions tend to form at the interface due to the behavior of the cobalt liquid phase, leading to segregation. To address this issue, a nickel powder layer was inserted as an intermediate layer to suppress the cobalt liquid phase behavior. As a result, the formation of pore regions was effectively prevented.