A large measured two-dimensional (2D) diffusion coefficient of gold nanoclusters on graphite has been known experimentally and theoretically for about a decade. When subjected to a lateral force, these clusters should slide with an amount of friction that can be measured. We examine the hypothetical possibility of measuring by quartz crystal microbalance (QCM) the phononic sliding friction of gold clusters in the size range around 250 atoms on a graphite substrate between 300 and 600 K. Assuming the validity of Einstein's relations of ordinary Brownian motion and making use of the experimentally available activated behaviour of the diffusion coefficients, we can predict the sliding friction and slip times as a function of temperature. It is found that a prototypical deposited gold cluster could yield slip times at the standard measurable size of 10(-9) s for temperatures around 450-500 K, or 200 degrees C. Since gold nanoclusters may also melt at around these temperatures, QCM could offer the additional chance of observing this phenomenon through a frictional change.
Gold clusters sliding on graphite: a possible quartz crystal microbalance experiment?
Tosatti E;Tartaglino U;Vanossi A
2007
Abstract
A large measured two-dimensional (2D) diffusion coefficient of gold nanoclusters on graphite has been known experimentally and theoretically for about a decade. When subjected to a lateral force, these clusters should slide with an amount of friction that can be measured. We examine the hypothetical possibility of measuring by quartz crystal microbalance (QCM) the phononic sliding friction of gold clusters in the size range around 250 atoms on a graphite substrate between 300 and 600 K. Assuming the validity of Einstein's relations of ordinary Brownian motion and making use of the experimentally available activated behaviour of the diffusion coefficients, we can predict the sliding friction and slip times as a function of temperature. It is found that a prototypical deposited gold cluster could yield slip times at the standard measurable size of 10(-9) s for temperatures around 450-500 K, or 200 degrees C. Since gold nanoclusters may also melt at around these temperatures, QCM could offer the additional chance of observing this phenomenon through a frictional change.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
