X-ray reflectvity uses total external reflection from surfaces and interfaces. It is useful for layer thickness between 5 and 350 Angstrom. It can give accurate layer thickness, density and roughness.  X-ray reflectvity measurements can be performed using a conventional power diffractometer [1].

XRR Scan of Thin ge Film on SI Substrate

 

The postions of the fringes are related to the film thickness by the modified bragg equation [1]

 

 

[1] Thin-film thickness and density determination from X-ray reflectivity data using a conventional power diffractometer HUANG T. C. ; GILLES R. ; WILL G. ;