High resolution x-ray diffration (HRXRD) is an ex-situ characterization method and it is the core tool to analyze nano-scale epitaxial structures. X-rays are produced from a source where electrons are ejected from a cathode, collide on a metal plate (in our case copper) and excite inner-shell electrons in the metal, resulting in the emission of strong spectral lines. The output is conditioned as a Cu Kα quasi-parallel beam, strikes on the crystalline sample at different incidence angles and the scattering signal is collected by a detector. The working principle behind HRXRD is Bragg’s law, which states that when the x-ray incident onto a crystal surface with angle of incidence, θ, it will reflect back with a same angle of scattering, θ. When the path difference, d is equal to a whole number, n, of wavelength, a constructive interference will occur. The path difference is the separation between the crystal planes that caused the reflection.
The Jordan Valey QC3 HRXRD system can be operated in different scanning modes: omega scan (rocking curve), detector scan, coupled scan and reciprocal space map. The data can be analyzed by a powerful software built with dynamic x-ray scattering models, where useful parameters such as layer thicknesses, composition, tilt and strain can be obtained upon curve fitting.