Observation of composition in surface monolayers by X-ray scattering spectra caused by crystal truncation and interferences.
X-ray crystal-truncation-rod (CTR) scattering measurements using synchrotron radiation and an imaging plate can reveal the composition of a surface monolayer. Even when the composition is changed in only one atomic layer on the top surface, the X-ray CTR spectrum can change due to the differences in composition. X-ray CTR spectra are greatly enhanced by X-ray interference when a sample is designed properly. In this paper, it is shown by theoretical calculations and experiments for AlAs/GaAs samples grown by MBE that a 1 ML (monolayer)-thick AlAs layer embedded under 10 ML below the surface can enhance the modulation of an X-ray CTR spectrum.