Micron and Submicron Patterning of Dicyanopyrazine-Linked Porphyrin Molecules Using Micro-Contact Printing and Langmuir-Blodgett Assembly

We describe a method to conveniently fabricate micron- and submicron-sized patterns of well-ordered and densely-packed dicyanopyrazine-linked porphyrin (4-TDCPP) molecules by using micro-contact printing (mu-CP) in conjunction with Langmuir-Blodgett (LB) deposition. SEM and AFM images reveal that the sizes and shapes of the 4-TDCPP patterns are well-matched with the geometric features of the polydimethylsiloxane (PDMS) stamps used for mu-CP. Fluorescence images show strong, red emission from the 4-TDCPP patterns. However, the thicknesses of the 4-TDCPP patterns transferred onto a silicon substrate by mu-CP are not the same, even though the same amount of 4-TDCPP layers are deposited on the surface of PDMS stamps in the LB process. The thicknesses of the 10 mu m line, 2 mu m dot and 300 nm line patterns of 10-layered 4-TDCPP molecules are 34.6, 26.7 and 5.9 nm, respectively. These differences may be due to variations in adhesion forces between the silicon substrate and 4-TDCPP on PDMS stamps having different size patterns. Larger patterns have greater contact areas compared to smaller patterns. This phenomenon can cause stronger adhesion forces, resulting in greater pattern thickness.