The energy-dispersive reflectometer at BESSY II: a challenge for thin film analysis

Installed in 1999 the energy-dispersive reflectometer at the 13.2 bending magnet employs the exponentially decaying white X-ray emission spectrum of the 1.7 GeV storage ring of BESSY II outside the vacuum. Using an energy-dispersive detector specular and longitudinal-diffuse reflectivity spectra of thin films can be recorded simultaneously between 0.2 Å−1<qz<1.2 Å−1 within a few seconds. pability of the experiment is demonstrated probing the correlation length of Cd-arachidate and -stearate films at room temperature and its change during annealing. At T=70°C we observe an instantaneous decay of specular Bragg peaks accompanied with an increase of the diffuse scattering. This indicates the onset of the melting of 2D-ordered acid domains. The vertical diffusion coefficient is estimated to be about 2×10−24 m2/s.