X-ray refractive index: A tool to determine the average composition in multilayer structures

Miceli, P. F.; Neumann, D. A.; Zabel, H.
January 1986
Applied Physics Letters;1/6/1986, Vol. 48 Issue 1, p24
Academic Journal
We present a novel and simple method to determine the average composition of multilayers and superlattices by measuring the x-ray refractive index. Since these modulated structures exhibit Bragg reflections at small angles, by using a triple axis x-ray spectrometer we have accurately determined the peak shifts due to refraction in GaAs/AlxGa1-xAs and Nb/Ta superlattices. Knowledge of the refractive index provides the average fractional composition of the periodic structure since the refractive index is a superposition of the refractive indices of the atomic constituents. We also present a critical discussion of the method and compare the values of the average fractional composition obtained in this manner to the values obtained from the lattice parameter change in the GaAs/AlxGa1-xAs superlattices due to the Al.


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