色散对GaN和ZnO的XRD摇摆曲线的影响

Influence of Dispersion on ZnO and GaN XRD Rocking Curves

在用X射线双晶衍射研究GaN和ZnO结晶性能的实验中,观察到(102)非对称衍射摇摆曲线的半峰宽比(002)对称衍射更窄以及ZnO(002)摇摆曲线分裂的现象.经研究证实,这是由于Kα2 线参与衍射引起的.通过计算Kα1 和Kα2 线在不同晶面衍射的分离角并与实验现象对比,阐明了GaN样品(102)半峰宽比(002)小以及ZnO(002)衍射峰分裂的原因.在此基础上,进一步分析了在使用不同参考晶体的双晶衍射系统中,GaN和ZnO的各晶面被X射线色散展宽的情况,并提出,在使用Si,Ge或GaAs的(220)面为参考晶面的双晶衍射仪中,GaN和ZnO的(002)和(102)面摇摆曲线的半峰宽受色散效应的影响小;而在使用Si,Ge或GaAs的(004)面为参考晶面的双晶衍射系统中,(002)和(102)面摇摆曲线的半峰宽受色散效应影响较大,此时(004)和(103)受色散影响小,因此用来表征晶体质量将更可靠.

Smaller FWHM of (102) rocking curve than (002) is observed in the double crystal XRD study of GaN films and peak splitting is observed in ZnO (002) rocking curves.By calculating the Kα 1-Kα 2 separation and comparing it with the distance of the two peaks in the ZnO (002) rocking curve,it is confirmed that these abnormal phenomena are introduced by the simultaneous diffraction of Kα 1 and Kα 2 lines.This is proved by the exact coincidence of the measured and calculated separation of high quality Si,GaAs,and sapphire crystal.Further analysis reveal that in double crystal diffraction systems using Ge(004),Si(004) or GaAs(004) as the reference crystal,the rocking curves of (004) and (103) plane of GaN and ZnO will be broadened much less by the wavelength dispersion than the commonly used (002) and (102) plane.So their FWHM will by more suitable indicator for the crystal quality of GaN and ZnO when use these diffraction systems.