Vertical Bridgman growth of sapphire—Seed crystal shapes and seeding characteristics

Abstract

The growth of sapphire by the traditional vertical Bridgman (VB) method was studied by using various shapes of seed crystals and tungsten (W) crucibles shaped to match the seeds. Approximately 2-inch diameter, c-axis sapphire single crystals were reproducibly grown from three kinds of seed: thin, tapered and full diameter. Factors relating seed type to single-crystal growth are discussed, including the reproducibility of seeding processes, and the generation and elimination of low-angle grain boundaries (LAGBs). What was learned facilitated the subsequent growth of large-diameter, 3-, 4-and 6-inch, c-axis single-crystal sapphires from full-diameter seeds.

Vertical Bridgman growth of Al2O3/YAG:Ce melt growth composite

“…We could confirm in Fig. 7 that just as the stereographic projections of Al 2 O 3 [11][12][13][14][15][16][17][18][19][20], [0001], and YAG [001], [À 112] show the same orientations as the seed, the Ce-doped MGC grown in the Mo crucible also retained the orientation of the seed. In contrast, we found that in Ce-doped MGC grown in an Ir crucible, while the orientation of the Al 2 O 3 phase was the same as the seed, however, the orientation of the YAG phase was inclined about 131 from that of the seed.…”

“…The crucible was mounted on a Mo crucible rod that can rotate and also translate vertically. A W/Re thermocouple was inserted in the crucible rod to measure the temperature of the crucible bottom [18]. The carbon heater was powered by high-frequency induction coils.…”

Morphology and formation mechanism of metallic inclusions in VB-grown sapphire crystals

“…Sapphire crystals, 50 mm in diameter and elongated along the c-axis, were grown by the VB technique using a tapered seed and a W crucible [11]. The furnace consisted of a graphite heater and carbon heat shields, and was filled with an atmosphere of 99.999 % pure argon gas (absolute pressure about 100kPa).…”

“…The crucible was slowly drawn downwards at 3 mm/h, the crystal growth being controlled by the rate at which the crucible was drawn down. Detailed growth conditions have been reported elsewhere [11].…”

Analysis of thermal stress through finite element analysis during vertical Bridgman crystal growth of 2 inch sapphire

“…VB 공정은 기존 HEM과 비교하여 hot zone 내 온도구배와 결정성장 속도의 제어가 용이하 며 [7][8][9], 성장시 hot zone 하단에 저온부가 형성되므로 CZ, KY 등의 공정과 비교하여 대류의 영향에서 자유로 운 장점이 있다. 또한 기판에 쓰이는 c-축 방향으로 직 접 성장이 가능하고 대구경화에 용이하여 향후 LED용 사파이어 기판 제조에 적극 활용될 것으로 기대된다 [10].…”