Increased Control over Gold Colloid Adsorption on Substrates for Colloid Displacement Lithography

摘要

Colloid displacement lithography is proving to be very effective in the designing of nanometer scale electronic devices. Precise control of the structure of matter at the nanometer scale has brought a revolutionary change in science and technology. The use of these nanometer scale devices ranges from the diagnosis of various diseases to cell repair to ultra strong materials. This research focused on optimizing the conditions for gold colloid particle adsorption for colloid displacement lithography, an expansion on gold colloid particle manipulation techniques using a scanned probe microscope. The system consists of a scrupulously cleaned glass surface that is coated with poly(diallyldimethylammonium chloride) (PDDA) and then with 5- or 10- nm gold colloid particles. The optimum conditions include the use of very low molecular weight PDDA (Avg MW u3c100,000 g/mol) or low molecular weight PDDA (Avg MW 100,000-200,000 g/mol) with an exposure time to the glass substrate of 120 to 150 minutes. This is then followed by a 24-hour exposure to the colloid solution. An atomic force microscope (AFM) is used to pattern the thus prepared colloid coated slides. In this work a variety of salts are used as potential blocking agents to prevent or modify the colloid adsorption. These include potassium iodide, potassium bromide, potassium chloride, sodium fluoride, sodiumsulfate, potassium hydrogen phosphate, potassium hydrogen phthalate, and sodium citrate.In summary, the following were found as a result of this work: The optimum conditions that lead to efficient patterning are: Low molecular weight PDDA with a coating time of 120 to 150 minutes.Exposure to 5-nm gold colloid for 24 hoursThe most interesting potential blocking agents are the phosphate, sulfate and citrate salts, as they show some potential for modifying the adsorption of the gold colloids on the PDDA.The dispersion of the colloid particles on the PDDA does not change when using the potential blocking agents compared to direct adsorption on the unmodified PDDA layer.The use of the potential blocking agents reduces the force required to pattern by a factor of 100 to 300.