Self-Assembly of Organic Molecules on Gold Surfaces

Increasing conductivity of organic thin-films via crystallization of organic molecules prompts developments in organic electronics. Organic molecules deposited onto surface reconstructions demonstrate self-organization on the surface, growing organic thin-films with large crystalline areas. To grow these films, we need atomically flat Au (111) with a surface reconstruction. As-received Au films on Si wafers were imaged using scanning tunneling microscopy (STM), revealing the surface as several curved mounds with no flat, reconstructed area. Post annealing at 100°C in either N2 or high vacuum, the Au mounds showed evidence of flattening into terraces ~500nm2 in size; however, this area was not sufficient for our purposes. Depositing Au onto the Au/Si sample via thermal evaporation was tested at deposition rates of 0.07Å/s-1.4Å/s and substrate temperatures of 30°C-100°C. At all deposition parameters, small islands formed on the surface, demonstrating that the deposition had no flattening effects. Au deposition was continued on mica substrates at 115°C and revealed small step edges at the surface. Continued testing of Au on mica at higher temperatures will be beneficial towards growing larger gold plateaus on the surface necessary for organic film growth.