钛宝石晶体中的位错以及退火对位错的影响

用化学腐蚀剂腐蚀出样品的 (0 0 0 1)表面上的位错蚀坑 ,在原生态和退火样品的对应径向线上测量了位错腐蚀坑的密度分布 .由位错腐蚀坑的形成理论确定出原生态晶体中很可能有 3种位错类型 ,即Burgers矢量b =13〈112 0〉 ,13〈110 1〉和〈10 10〉的位错线 ,然而长时间在还原性高温气氛中的退火难以降低晶体中的总的位错密度 .在晶体的放肩至等径生长阶段 ,沿着晶体的生长方向 ,晶体棒中心的位错密度由高变低 ,这显示出 :在晶体的放肩至等径生长的转变过程中 ,生长界面发生了翻转 ,由凹形界面转变为凸形界面 ,位错线随之从晶体棒的中心向边缘发散 .

DISLOCATION LINES IN DOPED-Ti SAPPHIRE CRYSTAL AND THE EFFECT OF ANNEALING

The dislocation lines in doped-Ti sapphire crystal and the effect of annealing on them are reported in this paper. By the aid of chemical etching method, the outcrops of dislocation lines are revealed in (0001) surface of doped-Ti sapphire crystal (Ti3+: Al2O3). The density distributions of dislocation lines were measured along with three corresponding radial lines in (0001) surface of the sample before and after annealing. Taking advantage of the forming thcory of dislocation etch-pit, three types of dislocation lines in as-grown crystal can be indicated, i.e. b = 1/3<1120>,1/3<1101> and <1010>. The annealing on crystal of long time in high temperature H2 atmosphere has effect on the first type of the dislocation line, but nearly no effect on other types of the dislocation lines. Therefore, the annealing on crystal hardly reduces the total density of the dislocation lines. During shoulder to equal radius growth, the densities of the dislocation lines at the center of crystal boule decrease from high to low along growth direction. During the following equal radius growth of crystal, the densities of the dislocation lines along radial direction of boule increase all through from low to high. This reveals the growth interface reversing fron concave to convex.