Dr. Bret N. Flanders
Oklahoma State University
Directed Electrochemical Nanowire Assembly
Tuesday, October 16, 2007
Directed Electrochemical Nanowire Assembly (DENA) technique is a single-step approach to fabricating metallic nanowires and interconnecting them with external circuitry. We have previously shown that these are near single crystalline metallic nanowires and that they interconnect with on-chip electrodes with very small contact resistances, of the order of 10 W.[1, 2] Here we identify dendritic solidification as an important component of the DENA process, and exploit this mechanism to realize diameter-tunable nanowire growth. The experimental parameter that provides this control is the frequency w of the alternating voltage that induces the DENA process. Increasing w increases the metal cation concentration gradient at the wire-solution interface, thereby increasing the growth velocity of the wire. In turn, the anti-correlation between growth velocity and tip-radius, a fundamental characteristic of dendritic solidification, gives rise to a wire of reduced diameter. For indium wires, increasing w from 0.5 to 3.5 MHz increases the growth velocity of the wires from 11 to 78 mm/s and reduces their diameter from 770 to 114 nm. Gold wires exhibit diameter-tunability that ranges from ~1 mm down to 45 nm. Thus, it is possible to tune the wire diameter from the microscale down to the nanoscale. Recent results on the user-specified directional growth of these nanowires will be presented, as well. This combination of capabilities will enable the future interrogation of the intrinsic transport properties of nanomaterials.
 Ozturk B, Mishima T, Grischkowsky D R and Flanders B N "Single step growth and low resistance interconnecting of gold nanowires," 2007 Nanotechnology 18, 175707.
 Talukdar I, Ozturk B, Mishima T D and Flanders B N "Directed growth of single crystal indium wires," 2006 Appl. Phys. Lett. 88, 221907.