Artificial opals consisting of polystyrene spheres ordered into a fcc lattice are grown with control over orientation and thickness. A thorough study of the formation of the pseudogap in these structures is carried out by means of reflectivity and transmission spectra. Special attention is paid to discriminate those features inherent to the photonic crystal, and those to the substrate on which the crystal is grown. Further, a characterization of the photonic band structure in the hexagonal facet of the Brillouin zone is made using angle resolved reflectivity measurements.

The structure and stability of alkanethiols self-assembled on Au(111) have been studied as a function of the molecular chain length by means of atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXD). Below saturation, phases consisting of molecules with different tilt angles and periodicities are formed. Differences in the mechanical stability of these phases are revealed by AFM experiments and discussed in terms of the competition between intermolecular and molecule-substrate interactions as a function of chain length. For long molecules, intermolecular interactions play a dominant role which stabilizes the formation of closed packed 30 degrees tilted ( radical 3x radical 3)R30 degrees structures. For short molecules, the van der Waals interaction with the gold substrate favors the formation of a 50 degrees tilted phase in which the molecules are arranged in a rectangular configuration.