Setup for in situ surface investigations of the liquid/glass transition with (coherent) x rays

A dedicated setup comprising an efficient cryogenic device for the in situ preparation of large surface areas of prototypical organic glass formers in a wide temperature range (170–340 K) is presented. This setup provides the necessary temperature and vibrational stability for surface x-ray and neutron scattering experiments, including the extremely sensitive technique of x-ray photon correlation spectroscopy (XPCS). XPCS is an emerging method which is made possible by the high coherent photon flux produced by third-generation synchrotrons. We demonstrate that microscopic motion at the surface can be studied in a direct way in the liquid and supercooled state using XPCS. In addition, we have used a charge-coupled-device detector to record two-dimensional images of static speckle patterns forming on surfaces in the glassy state.