Monitoring surface roughness during film growth using modulated RHEED intensity oscillations

Separation of the high- and low-frequency components of Reflection High-Energy Electron Diffraction (RHEED) intensity oscillations during pulsed deposition allows the extraction of a signal that is in phase with the cyclic surface morphology evolution during layer-by-layer growth. Similar to a biased impedance measurement in electricity, the periodic modulation of surface roughness induced by the pulsed deposition probes the differential response of the growth front to changes in step density. This signal does not follow the complex variation of the RHEED oscillation phase with diffraction conditions and surface reconstruction and therefore allows a direct detection of monolayer completion. Off-Laue Circle oscillations show promise to probe the surface morphology evolution at sharply defined in-plane spatial frequencies. •The modulation of the surface step density during pulsed deposition is used to probe the surface morphology.•The processed high-frequency signal has maxima at integer layer coverage, independent of the phase of the growth oscillations.•Off-Laue Circle oscillations contain information on the in-plane evolution of the surface morphology.•The algorithm is fast and numerically stable, offering the potential for real-time detection of monolayer completion.