We use thermal annealing to improve smoothness and to increase the lateral size of
crystalline islands of n-tetratetracontane (TTC, C 44 H 90) films. With in situ x-ray diffraction,
we find an optimum temperature range leading to improved texture and crystallinity while
avoiding an irreversible phase transition that reduces crystallinity again. We employ real-
time optical phase contrast microscopy with sub-nm height resolution to track the diffusion of
TTC across monomolecular step edges which causes the unusual smoothing of a molecular …