坩埚高径比对泡生大尺寸蓝宝石单晶的影响

Effects of crucible H/D ratio on large size Kyropoulos sapphire single crystal

研究了高径比分别为1.36和1.50的两组坩埚在炉体内的轴向、径向温度梯度和液流情况.在两组坩埚中进行晶体生长实验,将生长出来的晶体进行掏棒和切片,并对晶棒进行应力和气泡检测,对晶片进行位错和双晶摇摆曲线检测.对比理论计算和实验结果表明,当纵横温度变化近似一次函数,且纵横温度梯度作用下的固液面的夹角在45°~60°时,可以有效降低应力,减少开裂几率;当熔体内部只有一个涡旋的时候,可有效减少晶体气泡;坩埚高径比为1.36时,能有效降低位错密度,提高结晶性.

We investigate the effects of the crucible height to diameter ratio H / D on the quality of large size sapphire single crystal theoretically and experimentally. For two crucibles with H / D ratios of 1. 36 and 1. 50 we calculate the axial and radial temperature gradients and flow theoretically. We analyze the effects of two temperature fields on the growth of sapphire crystal in these two temperature fields. By comparing the theoretical calculation results with experimental results of these two temperature fields,the following conclusions are obtained： the stress and cracking probability are effectively reduced when the axial and radial temperature curves are close to linear function and the angle of solid surface is between 45° and 60° in the role of the axial and radial temperature gradient; the bubble inside the sapphire crystal is reduced when the melt has only one vortex; the dislocation density is reduced,and the crystallization quality is increased when the crucible H / D ratio is 1. 36.