A generalized methodology to analyse lattice-rod scans from helium atom scattering (HAS) has been developed, allowing in situ measurement of interlayer spacing during thin film growth. A Lomb periodogram technique is used to analyse the interference fringes observed in a lattice-rod scan of a stepped crystal surface. The algorithm is ideally suited to the small, unevenly sampled HAS data sets typically collected and has the advantage that the significance of peaks in the resulting frequency distribution can be calculated. We show how the method can be used to assess the significance of each interlayer spacing quantitatively. Using the growth of cobalt on copper(111) as an example, the statistical significance of the surface step height distribution is calculated directly. This paper represents a considerable improvement over existing fast Fourier transform-based methodologies.
Journal of Physics D: Applied Physics Vol. 35, p. 3216-3220