用提拉法生长的GdCa_4O(BO_3)_3晶体的结构缺陷研究

Investigation on Defects in GdCa_4O(BO_3)_3 Crystal Grown by Czochralski Method

利用相衬显微镜结合化学腐蚀法 ,进行了沿 0 10 方向提拉生长的GdCa4 O(BO3) 3(GdCOB)晶体中的缺陷观察。发现位错是 0 10 方向生长的晶体中的重要缺陷。在不同方向的晶体切片上观察了螺位错和刃位错蚀坑 ,位错塞积 ,平底蚀坑及尖底蚀坑。位错密度随晶体长度的变化而变化。在晶体的尾部观测到位错密度为 10 3/cm2 ,而在晶体的初始部位位错密度很低 ,只有 4 0 /cm2 。在晶体的X ,Z及 4 0 1 方向的切片的正反两面观察到的位错蚀坑现象完全不同 ,可以认为GdCOB晶体为单畴极性晶体 ,自发极化方向沿z轴方向。

The defects in GdCa 4O(BO 3) 3 (GdCOB) crystal grown by Czochralski method have been investigated by the phase contrast microscopy combined with chemical etching mehod.Dislocations are the main defects in ?010?direction grown crystals.Screw dislocation and edge dislocation etch pits,dislocation pileups,flat bottom and pyramid shaped etch pits were observed on different oriented crystal slices.The density of dislocations increase greatly with the crystal length from the top to the end.A high density of dislocations approximately 10 3/cm 2 were observed at the final growth stage while it was very low (40/cm 2 ) at the initial growth stage.The etched morphologies are quite different on the positive and negative sides of X ,Z and ?401?plates by which one can conclude that the GdCOB is a polar crystal with single domain and the spontaneous polarization is along z axis.