2025, Vol.35, No.4

Journal of the Korean Crystal Growth and Crystal Technology 2024 KCI Impact Factor : 0.2

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

This study investigates the effect of Czochralski (CZ) growth conditions on the structural and optical properties of high-purity CaF₂ single crystals, with a focus on application in deep ultraviolet (DUV) optical applications. Two (111) single crystals, grown under different pulling and cooling rates (C2308 and C2408), were compared to elucidate the influence of thermal gradients on residual stress development and defect formation. The C2408 (slow-pulling, gradual- cooling) condition reduced thermal gradients, resulting in the suppression of structural defects and stress birefringence. These results demonstrate that controlling growth and cooling rates is a critical factor in determining the overall structural and optical properties of CaF₂ single crystals, including crystallinity, stress-induced birefringence, and defect density.

This study investigates the effects of MoO₃ excess on the crystal structure and microstructure of MnTeMoO6 (MTMO), a candidate ULTCC material for high-frequency devices. MTMO powders were prepared by solid-state reaction with 0.5, 1.0, and 2.0mol% MoO₃ additions and sintered at 700°C. X-ray diffraction confirmed a single orthorhombic phase across all samples without secondary phases. SEM analysis suggested excess MoO₃ could modify the chemistry of interface liquids, reduce grain shape anisotropy, and regulate grain growth. This reduction in anisotropy is attributed to increased atomically disordered interfaces and a lowered critical driving force for grain growth, consistent with the predictions of two-dimensional nucleation and growth theory. The findings demonstrate that controlled MoO₃ addition enables microstructure tuning, improving process compatibility and performance for ULTCC applications.

This paper presents a numerical simulation of double diffusive convection in a rectangular enclousre during physical vapor transport of Hg₂Cl₂. The flow characteristics are numerically investigated as a function of the partial pressure of Br₂ at 10 Torr and 200 Torr at a temperature difference of 10°C (290°C→280°C) between the source and crystal regions, and the velocity vectors, streamlines, isotherms, and isomass concentration contours are presented. In addition, both the average Nusselt number and the average Sherwood number decrease linearly and exponentially, respectively, with increasing a partial pressure of Br₂. For pressures of Br₂ for 10 Torr and 200 Torr, the average Nusselt number in the crystal region is larger than in the crystal region, and conversely, the average Sherwood number in the crystal region is three times larger than in the source region.