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X-ray reflectivity analysis of thin films


X-ray reflectivity is a unique technique that can determine surface and interface roughness, film thickness, and the density of the thin film samples in a nondestructive manner. Rigaku's SmartLab® diffractometer has made X-ray reflectivity measurements a very simple task. The sample is precisely aligned automatically and the measurement conditions are optimized automatically based on sample information. All users have to do is input an approximate density range and sample size and the Guidance™ software package does the rest.


Shown below is an X-ray reflectivity curve measured from a WCN alloy film on a silicon substrate. Thickness fringes due to the interference of the X-ray beams reflected at the free surface and film-substrate interface are clearly observed. This experimental curve is fit to a model structure by Rigaku's GIXRR reflectivity software. From the fitting results, shown in the table, it seems that a reaction took place at the interface between the film and the substrate, resulting in a low density interfacial layer. The surface seems to have lower W concentration than the bulk. It is also seen that the film roughness has increased as growth proceeded.

Reflectivity curve measured