Andrew Jonathan Smith

Nanomechanics of single crystalline tungsten nanowires

Single crystalline tungsten nanowires were prepared from directionally solidified NiAl-W alloys by a chemical release from the resulting binary phase material. Electron back scatter diffraction (EBSD) proves that they are single crystals having identical crystallographic orientation. Mechanical investigations such as bending tests, lateral force measurements, and mechanical resonance measurements were performed on 100-300 nm diameter wires. The wires could be either directly employed using micro tweezers, as a singly clamped nanowire or in a doubly clamped nanobridge. The mechanical tests exhibit a surprisingly high flexibility for such a brittle material resulting from the small dimensions. Force displacement measurements on singly clamped W nanowires by an AFM measurement allowed the determination of a Youngs modulus of 332 GPa very close to the bulk value of 355 GPa. Doubly clamped W nanowires were employed as resonant oscillating nanowires in a magnetomotively driven resonator running at 117 kHz. The Youngs modulus determined from this setup was found to be higher 450 GPa which is likely to be an artefact resulting from the shift of the resonance frequency by an additional mass loading.

Copper Repassivation Characteristics in Carbonate-Based Solutions

bMax-Planck-Institut fur Eisenforschung, D-40237 Dusseldorf, Germany The present work reports on carbonate-based solutions, which can provide copper passivity in a wide potential range. This report focuses mainly on the identification of copper repassivation features obtained subsequent to mechanical damage of copper passive films in carbonate-based solutions. The repassivation rate of copper in carbonate-based solutions was measured with the use of a slurryjet system. The measured repassivation rate of copper in a slurryjet system utilizing a carbonate-based solution was found to be in the range of 1‐2 ms. An increase in the concentration of carbonate ions leads to a decrease of the copper repassivation time at potentials ranging from 200 to 600 mVAg/AgCl. The impingement angle between the copper surface and the single abrasive particle has an insignificant impact on the repassivation time and characteristics. It is therefore recommended that the use of carbonate anions as a passivating component in a future chemical mechanical planarization slurry design should be considered.