Faster acquisition of structure-factor amplitudes in surface X-ray diffraction experiments

The traditional way of measuring intensities in surface X-ray diffraction experiments is by performing rocking scans. Owing to experimental time limitations, this rather slow procedure leads to incomplete data sets for large surface unit cells. This lack of information not only may affect adversely the accuracy of the refined atomic positions, but also hinders the application of three-dimensional direct methods of structure solution. Here the viability of the alternative data collection strategy proposed by Specht & Walker [J. Appl. Cryst. (1993), 26, 166-171] is investigated by using as test material a 50 Å thick NBCO thin film grown on an SrTiO₃(001) substrate. This procedure, which is based on stationary L scans, i.e. the sample is kept fixed during the L scan, shortens the measuring time by an order of magnitude. In this study, special attention has been paid to the validation of the predicted theoretical Lorentz factor, which is specific for this experimental setup.