Thin film growth of tetracene on Ag(1 1 0) has been investigated by using scanning tunneling microscopy (STM). In the
monolayer regime, the tetracene molecules formed islands of ordered structure, which is commensurate (4-fold periodicity) in
the ½1 ¯10 direction, but incommensurate in the [0 0 1] azimuth, with the substrate. All the tetracene molecules align regularly
with their longer axes parallel to the [0 0 1] direction, and with their molecular planes parallel to the surface. At multilayer
coverages, the tetracene molecules form a crystalline film in a novel 3D orthorhombic structure, with their orientations remained
unchanged. Growth of tetracene on Ag(1 1 0) is in the layer-by-layer growth mode.
organic semiconductor , Epitaxial growth , Silver surface , Scanning tunneling microscopy