棱角对NH4H2PO4晶体Z切片薄表面层生长影响的研究

Effect of Edge Angles on Growth of Thin Surface Layer of Z-cut NH_4H_2PO_4 Crystal

本研究制备了具有不同形式棱角的NH_4H_2PO_4(ADP)晶体Z切片样品。通过实验,观察不同Z切片薄表面层形成及生长特性,并计算了不同棱角情况下薄表面层的切向生长速度V及其动力学系数β。结果表明,正常棱角的缺失,影响Z切片对其原有形态的"判断",进而影响薄表面层的形成及生长;薄表面层在正常棱角处相遇形成相交角后,将主要在相交角处形成并向棱边扩展生长,表明棱角可能为薄表面层的主要生长源。此外,计算结果显示,正常棱角处薄表面层切向生长的平均生长动力学系数β_n为131.8μm/s,远大于棱角缺失后薄表面层切向生长的平均生长动力学系数β_a=11.6μm/s,即正常棱角缺失后,薄表面层的切向生长速度将大大降低。

The Z-cut NH4H2PO4 （ADP） crystal plate samples with different types of edge angle were prepared. During crystal growth experiments, formation and growth characteristics of thin surface layers of different Z-cut plate samples were observed. Meanwhile, the tangential growth rate V and the corresponding kinetics coefficients β of thin surface layers were calculated in the present study. The results show that destruction of the normal angles has significantly influences on ＂judgment＂ of the original morphology ,of Z-cut plate, and further influence formation and growth of thin surface layers. When the thin surface layers meet with each other at normal edge angles, where the intersecting angles form, the thin surface layers generate mainly at intersecting angles and spread out along the edges. This phenomenon suggests that edge angles may be the main origin of thin surface layers. In addition, the average growth kinetics coefficient βn at normal angle is calculated to be 131.8 μm/s, much higher than 11.6 μm/s[0] ofβα at destroyed angle. These experimental and calculated results suggest that lack of normal angles remarkably decreases the tangential growth rate of thin surface layers.