Direct observation and localization of colloidal nanoparticles on patterned surface by capillary forces

Precise localization of nanoparticles is often required to fully exploit the intrinsic physical properties as well as to develop methodologies for large-scale integration of nanodevice building-blocks with the macroscopic world. In this work, a simple technique, based on control of capillary forces at the triple contact line during evaporation, was used to localize colloidal gold nanoparticles in pre-patterned resist holes on a silicon dioxide surface. By adjusting the surface contact angle and displacement speed of the contact line, pattern filling could be achieved for nanoparticles ranging from 10 to 100 nm in a range of hole and line patterns. We also show that after organization, the resist template can be removed by a dry O-2 plasma treatment to leave behind free-standing "nanowalls" of particles on the silicon dioxide surface. Finally, it demonstrated that the hole filling process can be followed dynamically by directly observing the evaporation process in situ as the three phase contact line is displaced over the resist pattern. (c) 2006 Elsevier B.V. All rights reserved.