Rapid-annealing method for growing large-size sapphire single-crystal with SAPMAC method

Abstract

The invention provides a rapid-annealing method for growing large-size sapphire single-crystal with the SAPMAC method. The SAPMAC method is adopted for growing sapphire single-crystal; after growing is finished, the vacuum degree of a crystal growing furnace is kept; electric power source is not cut off; heating power is lowered according to certain temperature reduction procedure until heating power is zero; and then inert gases are led in for rapid cooling. The invention has the beneficial effects that: 1. crystal dislocation density can be lowered, the lattice vacancy of crystal with big diameter and high expansion factor can be lowered, defect concentration such as distortion of lattice, dislocation and the like can be eliminated, crystal cleavage is avoided, and crystal quality and utilization factor can be improved; 2. in-situ annealing of crystal can be realized, crystal growing cycle can be shortened under the precondition of ensuring crystal quality; and 3. production cost can be lowered.

Description

(1) Technical field [0001] The invention relates to an annealing method for a single crystal, in particular to a rapid annealing method for growing a large-sized sapphire single crystal by a cold shoulder micro-pulling method. (2) Background technology [0002] The sapphire crystal grown by the melt method is required to be carried out at a temperature close to the melting point, so the grown crystal often has a large thermal stress, a serious lattice distortion, and poor optical uniformity. Therefore, the sapphire crystal must be annealed before processing and use to eliminate the original elastic deformation and crystal distortion, and reduce the thermal stress of the crystal. [0003] From a thermodynamic point of view, if the crystal contains a certain concentration of vacancies (depending on temperature), the free energy of the crystal will have a minimum value. The equilibrium vacancy concentration n can be expressed as: [0004] n~exp(-E v / kT) (1) [0005] In the...

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Problems solved by technology

[0012] It can be seen from formulas (1) and (2) that for crystals with large diameter and high expansion coefficient, in order to reduce the density of defects such as dislocations, reduce lattice distortion, and prevent cracking, a lower cooling rate must be used; however, another On the one hand, the reduction of cooling rate will inevitably prolong the annealing time and increase the production cost

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