| AVS 58th Annual International Symposium and Exhibition | |
| Tribology Focus Topic | Thursday Sessions |
| Session TR-ThA |
| Session: | Advanced Tribological Materials |
| Presenter: | Keeley Stevens, North Carolina State University |
| Authors: | K. Stevens, North Carolina State University J. Krim, North Carolina State University |
| Correspondent: | Click to Email |
Friction at the nanoscale shows a strong and complex relationship to surface roughness and atomic disorder [1]. Recent research in superconductivity dependent friction [2-5], along with reports that quantum size effects [6] can influence diffusion (and thus friction) of adsorbed layers, has motivated our investigation. In particular, we have performed friction measurements of adsorbed nitrogen and helium films sliding on nanostructured lead films substrates that have been deposited on titanium, a substrate that lead does not wet. Varying the lead coverage results in a spectrum of percolated morphologies. We prepare these films on a quartz crystal microbalance (QCM) and probe their topologies by means of adsorption onto the surface [7].
Measurements have been recorded on nanoclustered lead films with coverages crossing the critical concentration for percolation. We study the substrate in the superconducting and normal states, which allows us to isolate and quantify the contribution of electronic and phononic dissipation to the total friction present [2]. Submonolayer adsorbate converages have allowed us to probe the edge effects of surface nanoclusters, while multilayer coverages have let us explore the strength and proximity effects of surface roughness. We compare our measurements to those reported by Pierno et al. on films of ordered Pb(111) terraces, where atomic step edges are present [3], and conclude that the variation in reported values of friction on nanostructured lead is due to phononic effects at the step edges.
Funding provided by NSF DMR.
[1] Y. Braiman et al., Physical Review E 59, R4737-40 (1999).
[2] M. Highland and J. Krim, Physical Review Letters 96, 1-4 (2006).
[3] M. Pierno et al., Physical Review Letters 105, 1-4 (2010).
[4] Q. Ding et al., Wear 265, 1136-1141 (2008).
[5] M. Kisiel et al., Nature Materials 10, 119-122 (2011).
[6] M. Özer et al., Physical Review B 72, 3-6 (2005).
[7] V. Panella and J. Krim, Physical Review E 49, 4179-4184 (1994).