Highly <111>-oriented diamond films with azimuthal alignment were successfully deposited on platinum{111}/iridium{111}/platinum{111} formed on sapphire{0001} by microwave enhanced chemical vapor deposition. With oriented nucleation density of approximately 1x10 8 cm - 2 , the heteroepitaxial {111}-oriented diamond films were grown over a 10x10 mm 2 area without crack or delamination from the substrate. X-Ray diffraction rocking curve of diamond{111} has a full-width at half maximum value of 1.1 o , which endorses a high crystal quality of the diamond film. The high density of oriented nucleation and improved adhesion of the diamond can be attributed to the Ir film inserted between the two Pt layers, which hinders diffusion of carbon through the Pt and graphite formation at the Pt/sapphire interface.