Aug 6, 2009
All-metal probes advance AFM capabilities
The use of conductive tips in atomic force microscopy (AFM) has become increasingly important with applications ranging from electrochemical nanolithography to ferroelectric data storage. Unfortunately, the current approach of fabricating conductive tips via thin metal coatings can lead to increased tip radius and low device lifetime. Finding a way to overcome these limitations is of key importance.
To tackle the issue, researchers at the University of Alberta, Canada, and NINT NRC, US, have designed a thin-film copper-hafnium alloy with attributes optimized for AFM-probe applications. Films are deposited using co-sputtering and subsequently patterned into AFM probes using optical lithography.
A unique combination of mechanical, surface and electrical properties, owing to the glassy microstructure of the alloy, allows for the microfabrication of conductive and optically reflective AFM probes of arbitrary sizes and geometries. The realized devices have a 10 nm tip radius, which is competitive with silicon and SiN-based conventional AFM cantilevers.
In the past, fabrication of all-metal cantilevers has proved practically impossible due to cantilever curling caused by differential stresses developed during polycrystalline grain growth. This critical problem is circumvented in this design because the optimized copper-hafnium glassy films possess minimal stress gradients.
Successful imaging using these next-generation AFM probes was performed, demonstrating the feasibility of all-metal AFM probes and their potential for advancing the capabilities of numerous AFM technologies.
The researchers presented their work in Nanotechnology.
About the author
Erik Luber is a PhD student in the Department of Chemical and Materials Engineering at the University of Alberta, an Alberta Ingenuity Scholar and an NSERC Scholar. Dr David Mitlin is an associate professor in the Department of Chemical and Materials Engineering and a PI at NINT NRC. The group's research focus is on the synthesis and structure-property relations in nanostructured metallic composites for a variety of applications.