Method for Determining Crystal Grain Size by X-Ray Diffraction

The crystalgrain size can be quantitatively calculated by Scherrer equation according to the diffraction peak broadening in the XRD curves. Actually, the results calculated by the Scherrer equation are the thickness that perpendicular to the crystal planes. However, in the actual XRD measurements, the broadening of the diffraction peaks is not only because of the Micro-level changes of crystal such as grain size and lattice distortion, but also due to the instrumental broadening. Thus, the Scherrer equation is less reliable if the full width at half maximum caused by the physical broadening is smaller than that caused by the instrumental broadening. In this paper, it is concluded that the applicable range of the Scherrer equation will increases with the increasing diffraction angle. As an example of Scherrer equation's application, the calculation result for the maximum applicable scope of Si(100) films is 137nm.