Nanoindentation unidirectional sliding and lateral force microscopy: evaluation of experimental techniques to measure friction at the nanoscale

CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERG - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SULFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOLateral force microscopy (LFM) is an established technique to assess friction forces at the nanoscale. Nanoindentation followed by unidirectional sliding (NUS) is also used to evaluate friction forces at the micro/nanoscale. However, comparative studies between NUS and LFM evaluating the experimental results at different scales are still missing. In this work, a-C:D/H and a-C:H thin films with different [D]/[C] and [H]/[C] contents were used to analyze the friction forces by NUS and LFM. The results show that the friction behavior assessed by these two techniques in different scales is the same. The correlation between friction forces measured by NUS and LFM depends mainly on a contact area factor that makes invariant the friction force from nanoscale to microscale. Such behavior suggests a similar damping mechanism, probably phonon-coupling phenomena, for the friction force origin.812110CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERG - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SULFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERG - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SULFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO465423/2014-0sem informação2012/10127-

Influence of base pressure prior to deposition on the adhesion behaviour of carbon thin films on steel

The poor adhesion of carbon thin films was the main restriction for its massive application in recent years. Physicochemical interaction improvement at the adhesion interface between substrate and thin film is one of the most important fields of research to overcome such problem. From a chemical point of view, oxygen seems to be a major issue in the adhesion control. In this work, the influence of base pressure prior to deposition process on the carbon thin film tribological behaviour was studied. Rockwell C and scratch tests were performed to qualify the thin film failures and adhesion. Chemical mapping was performed by energy-dispersive spectroscopy to characterise the chemical elements after thin film failure. The carbon thin films show better adhesion at lower base deposition pressures. The tribological behaviour is associated with the oxygen content in the chamber atmosphere as well as to the higher thin film adhesion achieved at lower base pressures

Nanoindentation unidirectional sliding and lateral force microscopy: Evaluation of experimental techniques to measure friction at the nanoscale

Lateral force microscopy (LFM) is an established technique to assess friction forces at the nanoscale. Nanoindentation followed by unidirectional sliding (NUS) is also used to evaluate friction forces at the micro/nanoscale. However, comparative studies between NUS and LFM evaluating the experimental results at different scales are still missing. In this work, a-C:D/H and a-C:H thin films with different [D]/[C] and [H]/[C] contents were used to analyze the friction forces by NUS and LFM. The results show that the friction behavior assessed by these two techniques in different scales is the same. The correlation between friction forces measured by NUS and LFM depends mainly on a contact area factor that makes invariant the friction force from nanoscale to microscale. Such behavior suggests a similar damping mechanism, probably phonon-coupling phenomena, for the friction force origin