Tribology of Dendrimer-based Metal Nanocomposites: Influence on Critical Load
X. Li, M. Curry, S. Street and M. Weaver
We continue our study of the tribology of dendrimer-based metal nanocomposites and the use of dendrimer underlayers to control oxidation and grain size in metal overlayers. The focus of the current tribology work is on reactive metal overlayers, particularly Ti and Al. Recent results have shown that while Ti itself adheres very well to silica substrates, the dendrimer-mediated Ti film shows an even higher critical load (film failure, see Figure below) in ramped load scratch tests. Thus, even though the dendrimer interlayer does not improve adhesion in this case (as it did with Cu overlayers, previously reported), the composite film still shows improved nanotribological behavior. We have also shown that the dendrimer interlayer modifies the grain growth of metal overlayers. Apparently, this morphology change arises because the dendrimer monolayer restricts lateral diffusion of the deposited metal atoms and in some cases chemically reacts with the incoming metal, forming an interfacial layer which modifies subsequent metal grain growth. We are also studying the ability of the dendrimer-based metal nanocomposite to resist oxidation and retain native electrical conductivity.