Nanotechnologists form near-frictionless diamond material

Feb 25, 2010
This is an SEM image of a silicon microcantilever with an ultrasharp tip of diamond-like carbon with silicon. Credit: Harish Bhaskaran, IBM

Researchers at the University of Pennsylvania, the University of Wisconsin-Madison and IBM Research-Zürich have fabricated an ultra sharp, diamond-like carbon tip possessing such high strength that it is 3,000 times more wear-resistant at the nanoscale than silicon.

The end result is a diamond-like carbon material mass-produced at the that doesn't wear. The new nano-sized tip, researchers say, wears away at the rate of one atom per micrometer of sliding on a substrate of , much lower than that for a tip which represents the current state-of-the-art. Consisting of carbon, hydrogen, silicon and oxygen molded into the shape of a nano-sized tip and integrated on the end of a silicon microcantilever for use in , the material has technological implications for atomic imaging, probe-based and as emerging applications such as nanolithography, nanometrology and nanomanufacturing.

The importance of the discovery lies not just in its size and resistance to wear but also in the hard substrate against which it was shown to perform well when in sliding contact: silicon dioxide. Because silicon -- used in almost all integrated circuit devices -- oxidizes in atmosphere forming a thin layer of its oxide, this system is the most relevant for nanolithography, nanometrology and nanomanufacturing applications.

Probe-based technologies are expected to play a dominant role in many such technologies; however, poor wear performance of many materials when slid against silicon oxide, including silicon oxide itself, has severely limited usefulness to the laboratory.

Researchers built the material from the ground up, rather than coating a nanoscale tip with wear-resistant materials. The collaboration used a molding technique to fabricate monolithic tips on standard silicon microcantilevers. A bulk processing technique that has the potential to scale up for commercial manufacturing is available.

Robert Carpick, professor in the Department of Mechanical Engineering and Applied Mechanics at Penn, and his research group had previously shown that carbon-based thin films, including diamond-like carbon, had low friction and wear at the nanoscale; however, it has been difficult to fabricate nanoscale structures made out of diamond-like carbon until now.

Understanding friction and wear at the nanoscale is important for many applications that involve nanoscale components sliding on a surface.

"It is not clear that materials that are wear-resistant at the macroscale exhibit the same property at the nanoscale," lead author Harish Bhaskaran, who was a postdoctoral research at IBM during the study, said.

Defects, cracks and other phenomena that influence material strength and wear at macroscopic scales are less important at the nanoscale, which is why nanowires can, for example, show higher strengths than bulk samples.

The study is published in the current edition of the journal Nature Nanotechnology.

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User comments : 4

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danman5000
not rated yet Feb 26, 2010
So where was the part about it being frictionless like the title says?
eldowan
Feb 26, 2010
This comment has been removed by a moderator.
eachus
not rated yet Feb 27, 2010
danman5000 asked: So where was the part about it being frictionless like the title says?

"The new nano-sized tip, researchers say, wears away at the rate of one atom per micrometer of sliding on a substrate of silicon dioxide, much lower than that for a silicon oxide tip which represents the current state-of-the-art."

One million atoms lost per meter may sound like a lot, but think of running a phonograph needle over a piece of sandpaper. How many millimeters before you have no point left? With the phonograph needle, even a diamond stylus you would be losing material a million or more times as fast.
NeilFarbstein
not rated yet Mar 01, 2010
so what? silicon is soft and easily abraded.
3000 times the hardness if silicon is not impressive
macroguru
not rated yet Mar 25, 2010
so what? silicon is soft and easily abraded.
3000 times the hardness if silicon is not impressive

actually, silicon is an impressively hard material, it is not soft at all. in fact in vacuum, silicon probes are incredibly wear resistant. also soft has little to do with wear. rubber is soft too but it is used in tires.