USING AMOSOV METHOD FOR GROWING MONOCRYSTALS FROM MELT Russian patent published in 2005 - IPC

FIELD: crystal growing.

SUBSTANCE: invention relates to technology of growing monocrystals seed crystal and can be used for growing monocrystals having different chemical composition, e.g., types A₂B₆ and A₃B₅, as well as monocrystals of refractory oxides, for instance sapphire. In a method preparing monocrystals by growing them from melt comprising melting starting material and drawing monocrystal by crystallization of melt on seed crystal at controlled removal of crystallization heat and use of independent heating sources forming own heat zones, according to invention, independent heating sources form two equal-sized coaxially disposed heat zones so that unified thermal melt and grown crystal region is created separated by melt mirror. Starting material is melted in two steps: first upper heat zone is heated by feeding upper heater with 50% power required to produce melt until maximum temperature providing stable state of seed crystal solid phase is attained, after which the rest of power is directed to lower heat zone onto lower heater at unchanged temperature of upper heat zone until batch is completely melted. Enlargement and growth of monocrystal proceed at controlled lowering of temperature in upper heat zone and preserved unchanged power fed into lower heat zone. Furthermore, crystallization heat is removed in crystal enlargement and growth step at a velocity calculated from following formula: g/sec, where Δm denotes crystal mass, g; Δτ denotes mass growth (Δm) time; T_melt melting temperature of starting material, °C; T_crit maximum temperature of stable state of seed crystal solid phase, °C; ΔT temperature change in upper heater in the process, °C; ΔH_melt specific melting point, cal/g; ρ pressure const; R crystal radius, cm; A = ΔT/ΔR is radial temperature gradient near crystallization zone, °C/cm; is initial axial temperature gradient in crystal growth zone, °C/cm; C_p specific heat capacity, cal/g-°C'; and λ heat conductivity of crystal, cal/cm-sec-°C.

EFFECT: achieved independence of process of grown monocrystal material, increased productivity, and increased structural perfection of monocrystal due to lack of supercooling in the course of growth.

2 cl