The Effect of Atomic-Scale Roughness on the Adhesion of Nanoscale Asperities: A Combined Simulation and Experimental Investigation
- 1.5k Downloads
The effect of atomic-scale roughness on adhesion between carbon-based materials is examined by both simulations and experimental techniques. Nanoscale asperities composed of either diamond-like carbon or ultrananocrystalline diamond are brought into contact and then separated from diamond surfaces using both molecular dynamics simulations and in situ transmission electron microscope (TEM)-based nanoindentation. Both techniques allow for characterization of the roughness of the sharp nanoasperities immediately before and after contact down to the subnanometer scale. The root mean square roughness for the simulated tips spanned 0.03 nm (atomic corrugation) to 0.12 nm; for the experimental tips, the range was 0.18–1.58 nm. Over the tested range of roughness, the measured work of adhesion was found to decrease by more than an order of magnitude as the roughness increased. The dependence of adhesion upon roughness was accurately described using a simple analytical model. This combination of simulation and experimental methodologies allows for an exploration of an unprecedented range of tip sizes and length scales for roughness, while also verifying consistency of the results between the techniques. Collectively, these results demonstrate the high sensitivity of adhesion to interfacial roughness down to the atomic limit. Furthermore, they indicate that care must be taken when attempting to extract work of adhesion values from experimental measurements of adhesion forces.
KeywordsAdhesion Surface roughness In situ TEM Molecular dynamics simulation Nanotribology AFM Diamond Diamond-like carbon
The authors wish to thank Dr. Doug Yates and Dr. Ryan Major for microscopy and equipment assistance, and Prof. Mark O. Robbins for helpful discussions. The authors thank Graham E. Wabiszewski for assistance performing AFM on the indenter tip. Use of the facilities of the Pennsylvania Regional Nanotechnology Facility is acknowledged. The authors acknowledge funding from the National Science Foundation under the following Grants: CMMI 0826076 (RWC); IGERT DGE 0221664 (TDBJ); DMR 1120901 (RWC); CMMI 0845294 (KTT); CMMI 0825981 (JAH, PLK, KER); CMMI 1200019 (KTT, RWC); CMMI 1200011 (JAH); and IAA 1129629 (JAH, PLK, KER). KER and PLK also acknowledge partial support from the Office of Naval Research through the US Naval Academy. The support of AFOSR under Contract No. FA2386-11-1-4105 AOARD is also acknowledged (RWC).
Supplementary material 2 (MOV 225558 kb)
- 1.Israelachvili, J.N.: Intermolecular and Surface Forces, 3rd edn. Elsevier, San Francisco (2010)Google Scholar
- 30.Johnson, K.L.: Contact Mechanics. Cambridge University Press, London (2011)Google Scholar
- 34.LAMMPS Molecular Dynamics Simulator. http://lammps.sandia.gov/
- 42.Liu, J., Grierson, D.S., Sridharan, K., Carpick, R.W., et al.: Assessment of the mechanical integrity of silicon and diamond-like-carbon coated silicon atomic force microscope probes. In: Proceedings of the SPIE–The International Society for Optical Engineering, vol. 7767, p. 776708 (2010)Google Scholar
- 44.Fletcher, P.C., Felts, J.R., Dai, Z., Jacobs, T.D., et al.: Wear-resistant diamond nanoprobe tips with integrated silicon heater for tip-based nanomanufacturing. Am. Chem. Soc. Nano 4, 3338–3344 (2010)Google Scholar