Self-alignment of Gold Nanoparticles through the Control of Particle-substrate and Particle-particle Interactions

Abstract

Gold (Au) nanostructures have been fabricated on various substrates, such as Si, ITO and quartz glass, through the position-selective deposition of Au nanoparticles. This self-aligned deposition of the nanoparticles is promoted through the electrostatic interaction between the nanoparticles and the deposition sites, which are charged negatively and positively, respectively. Prior to the nanoparticle deposition, the positively charged sites where covered with aminosilane self-assembled monolayer had been constructed on the substrate with an artificial pattern design by a lithographic method. A photolithographic process, which was based on direct photochemical modification of organic substances induced by irradiating with a vacuum ultra-violet (VUV) light, was employed so that sub-μm features down to 500nm have been successfully fabricated and provided as templates for aligning Au nanoparticles. The second method for patterning was electrochemical line drawing using a scanning probe microscope. One-dimensional arrays of Au nanoparticles with a line thickness of a single nanoparticle diameter have been successfully fabricated. In addition, by replacing a surface charged layer consisting of citric acid molecules surrounding the Au nanoparticles with alkanethiol molecules, the Au nanoparticles were neutralized so that the fabricated Au nanoparticle array in which most of the nanoparticles were separated each other was re-organized to a more closely packed structure.