STM Investigation of Phthalocyanines as Possible Building Blocks for Quantum-Dot Cellular Automata

Ultra-high-vacuum scanning tunneling microscopy was used to observe copper phthalocyanine molecules deposited on the Au(111) surface. The primary goal of these experiments was to isolate a single copper phthalocyanine so that its electronic properties could be studied closely with the molecule not interacting with any other surface bound molecules. There where several issues that had to be addressed satisfactorily before the microscope would be ready to scan single molecules. These steps included fabricating a support structure for the instrument, and eliminating or minimizing all sources of external noise. Several samples were used to calibrate the microscope and verify that the instrument could image atomic-scale features. Dip-casting was used to create Au(111) samples with low coverages of copper phthalocyanines. We optimized the experimental parameters used to acquire images, including bias voltage, tunneling current, and scan speed; this optimization was done to maximize resolution, contrast, and tunneling stability. STM imaging of single copper phthalocyanine molecules was demonstrated.