Progress in surface X-ray crystallography and the phase problem

With the increase in the brilliance of synchrotron radiation sources, diffraction techniques have grown and expanded the scientific field of application. Surface X-ray diffraction (SXRD) is one of the state-of-the-art techniques to determine the constellations of atoms on crystal surfaces including adsorbates, thin films, and relaxed layers. We briefly overview SXRD and review the recent advances over decades from both experimental and theoretical viewpoints, including fast observations and imaging surface atoms.