We studied the growth of pentacene (C22H14) on the Au(110) surface by means of He atom scattering and Synchrotron X-ray photoemission. We found that two-dimensional commensurate growth only occurs in the monolayer range for a substrate temperature, T-s, higher than similar to 370 K. Larger amounts of deposited molecules forms three-dimensional uncorrelated clusters on the wetting layer. The desorption of second layer molecules occurs at T-s >= 420 K. The highest coverage ordered phase displays a (6 x 8) symmetry and corresponds to the saturation coverage at T, = 420 K. The (3 x 6) symmetry phase, recently reported for a multilayer planar film [Ph. Guaino, et al. Appl. Phys. Lett. 2004, 85, 2777], is only found at a coverage slightly lower than the (6 x 8) one. The (3 x 6) phase corresponds to the saturation coverage of the first layer at T-s = 470 K.
