Organic Fluorescent Molecules Patterning Based On Monolayer Patterns Directed Assembly

Organic light emitting molecules have been widely used in the fields of light emitting diodes, displays and other optical devices due to their low cost and wide applicability,which has attracted intensive research interests. For the fabrication of integrated organic electronic devices, information storage, sensors, organic field-effect transistor, it is important to pattern organic materials over large areas with high resolution. Organic luminescent molecules are used in fabricating organic film via gas deposition. Micromachining Technology is firstly applied in fabricating organic luminescent molecules, and the conventional method for micropatterning small-molecule films is based on shadow mask technology. Unfortunately, this method has limitations in achieving high resolution because of shadow effects and presents difficulties in applying over a large area. Several alternative patterning methods have also been developed, such as photolithography, microcontact printing (μCP), organic vapor jet printing , cold welding, soft lithography, and nanosphere lithography, electron-beam lithography, ion-beam lithography and so on. As an emerging technique, nanoimprint lithography provides a way to fabricate low-cost, high-throughput, high-resolution pattern.Besides the top-down fabrication methods, fabrication of organic light emitting molecules patterns based on bottom-up methods has received more and more attention. Templated assembly method is used in fabrication of organic material pattern gradually. Self-assembly monolayers (SAM) achieved great success in supramolecular assembly system. Organic silane molecules connect with the substrate by covalent bonding with high stability. Organic silane pattern make the surface functional. Template-directed growth of organic materials in gas phase can avoid ambient contamination (water and oxygen), and be readily compatible with matured semiconductor processing technology.In this work, we used patterned self-assembled monolayer (SAM) fabricated by NIL as a template to direct the deposition of organic luminescent molecules .The study follows:1. Based on nanoimprint lithography, APTMS SAM pattern was achieved on silicon substrate, which directed the deposition of organic luminescent molecules via gas phase deposition and studied the effect of morphology, molecule deposition, storage time, geometry of the pattern, and substrate temperature on the aggregation of organic luminescent molecules. Deposit organic luminescent molecules via gas phase deposition onto the SAM decorated Si substrate. At first molecules deposited on the sample surface disorderly, including the APTMS regions and substrate surface. With extending the storage time, the organic luminescent molecules move onto the APTMS monolayer from Si substrate and form a thin uniform organic film. I control the substrate temperature by heating the substrate in evaporation process. The amount of the molecules domain between the lines decreased and molecules move faster with the temperature increased, but the molecules domain between the APTMS lines became larger. At the same time, organic luminescent molecules can move onto the APTMS SAM. The distance that organic luminescent molecules can move is limited. In a certain time, the largest distance is fixed. The number of organic luminescent molecules that the APTMS SAM can contain is a certain value. The larger the SAM area is, the more molecules it can contain. Organic luminescent molecules can be deposited onto the APTMS SAM by fabricating APTMS pattern with proper geometry, achieving selective deposition of organic luminescent molecules. In this way, well-ordered organic luminescent molecules patterns were fabricated. Two kinds of substrate were chosen in the experiment and three kinds of organic luminescent molecules were selected, which achieved similar results. It proves that the method can be used with other different organic light emitting molecules. This versatile method provides a promising route for large area patterning of organic light emitting molecules with high resolution and high throughput.2. PMMA monolayer was fabricated on silicon substrate via nanoimprint lithography without deposition of APTMS via gas phase deposition. Deposite organic luminescent molecules via gas phase deposition and do research into morphology and selective deposition of molecules. It was found that the experiment results when organic luminescent molecules deposited on the PMMA were similar with that of deposition onto the APTMS SAM. With increasing the time, molecules move to the PMMA monolayer. The distance molecules can move is limited and the number of molecules PMMA monolayer can contain is related to the area of monolayer. By fabricating PMMA pattern with proper geometry, selective deposition of organic luminescent molecules can be achieved with orderly organic luminescent molecules patterns fabricated.3. Three kinds of monolayer were fabricated: APTMS, FDTS, PMMA monolayer. I made comparison on the morphology and selective deposition during the research. Deposite organic luminescent molecules via gas phase deposition on three kinds of monolayer with no structure. It is easier to form a uniform thin film on APTMS and PMMA monolayer, and form many organic domains on FDTS monolayer. We make different kinds of SAM pattern for compare the influence of different SAM to the organic molecules. We found FDTS monolayer had the lowest surface energy, so the molecules would deposite on the other monolayers, and the organic molecules prefer to deposite the APTMS monolayer, because of its highest surface energy.In conclusion, a template-directed method for patterning organic light emitting molecules is demonstrated. Based on Nanoimprinting Lithography, the self-assembled monolayer pattern provides different surface energies, and induces organic light emitting molecules depositing on anticipated positions. This versatile method provides a promising route for large area patterning of organic light emitting molecules with high resolution and high throughput.