Near room temperature self-assembly of nanostructures by reaction of gallium with metal thin films.

NEAR ROOM TEMPERATURE SELF-ASSEMBLY OF NANOSTRUCTURES BY REACTION OF GALLIUM WITH METAL THIN FILMS Mehdi M. Yazdanpanah July 28, 2006 Liquid gallium (Ga) spontaneously alloys with thin films of metals such as Ag, Au, Pt AI, and Cu at near or even below room temperature resulting in rapid self-assembly of nanostructures. In this dissertation, studies of the formation of these nanostructures are reported together with application of the processes towards device fabrication. Ag2Ga needles, CoGa3 rods, and G~Pt plates self-assemble at room temperature at the interface of Ga and thin films of Ag Co, and Pt. The Ag2Ga needles orient nearly vertical to the interface which suggests that an individual needle can be directed to grow in a desired direction by drawing a silver-coated surface from the Ga droplet. Needles from 25 nm to microns in diameter and up to 33 microns long were grown by this method. Needle-tipped cantilevers have been used to perform atomic force microscopy (AFM) and voltage lithography. Mechanical properties of the Ag2Ga needles are measured during bending, buckling, yielding, and AC electric excitation of vibrational modes. The rates of reactive spreading of Ga through thin films of Au and Ag from room temperature to 200°C are measured. A model of the reduction in spreading rate of Au-Ga over time describes the reduction in area for inter granular flow as the Ga2Au crystallites precipitates and grow together. Ga spreading on Au microelectrodes is used to perform