Adhesion detachment and movement of gold nanoclusters induced by dynamic atomic force microscopy

G. Paolicelli, K. Mougin, A. Vanossi, S. Valeri

J. Phys.: Condens. Matter 20 (2008) 354011

Purpose of Study:

This study used dynamic atomic force microscopy in tapping mode to investigate the adhesion and frictional properties of nanoclusters deposited on a surface. 

 

Methods:

Atomic force microscopy was used in tapping mode with amplitude feedback (AM-AFM), meaning that the AFM was performed by measuring and controlling the energy released by the AFM tip to the system while moving across a surface.  In this case, the amplitude oscillation was made larger than that optimal for imaging purposes in order to measure the energy dissipated when the nanoclusters bound to the surface detach as a result of the extra energy.  In this way, the group was able to measure the adhesion properties of gold nanoclusters on a Si (100) surface.

Experiments were performed in air at room temperature using a VEECO Enviroscope and Nanoscope IV.  Two standard silicon cantilevers were used with nominal frequencies of 75 and 350 kHz, and spring constants of 3 and 40 N/m. 

 

Key Findings:

1.       The AM-AFM technique provides the ability to measure the energy detachment threshold for Au nanoclusters down to the 10 nm scale.

2.       The AM-AFM technique provides information on different types of detachment techniques, including collisions between moving and pinned particles, and a detachment track of sets of nanoclusters.

3.       This analysis proves that the adhesion energy of nanoclusters depend on their size down to the contact area of 10² nm².