Abstract:

Carbon-based thin solid films, including nanocrystalline diamond and diamond-like carbon (DLC), are an important class of “solid lubricants”: materials that can exhibit extremely low friction (more slippery than ice) and wear (100’s of times more wear-resistant than well-lubricated steel). Applications include aerospace and automotive components, computer hard disks, and nanoscale mechanical devices for logic and lithography. In this talk, I will provide a general overview of the formation, structure, composition, properties, and technological applications of these materials.

I will then focus on two specific scientific issues that limit the applicability of these materials. First, I will discuss how the thermal stability of DLC-based materials is a key concern, particular for next-generation hard disks. SiO_x-doped DLC’s may provide a solution, as they exhibit better thermal stability than typical hydrogenated DLC’s. However, the scientific basis for this behavior is not established. To explore this, we are investigating the structure, bonding, and composition of these materials as a function of temperature, including through the use of an advanced surface science apparatus we have developed ¹, which includes an environmental X-ray photoelectron spectrometer (E-XPS) able to acquire spectra at elevated pressures (up to 0.4 Torr) and temperatures.

Second, I will discuss new insights into the nanoscale wear mechanisms for these materials. I will show that these ultrastrong carbon-based materials can be used to be greatly reduce nanoscale wear compared to their conventional silicon-based counterparts^2,3. I will also discuss the characterization of nanoscale wear in situ using a transmission electron microscope. Nanoscale probes composed of the materials of interest are slid against a flat diamond substrate. The shape evolution and volume loss due to wear are well described by kinetic model based on stress-assisted bond breaking mechanisms, allowing new insights to be gained about the kinetics of atomic-scale wear^4,5.

1.            Mangolini, F., Ahlund, J., Wabiszewski, G.E., Adiga, V.P., Egberts, P., Streller, F., Backlund, K., Karlsson, P.G., Wannberg, B. and Carpick, R.W. Angle-resolved environmental x-ray photoelectron spectroscopy: A new laboratory setup for photoemission studies at pressures up to 0.4 torr. Rev. Sci. Instrum. 83, 093112-093110 (2012).

2.            Bhaskaran, H., Gotsmann, B., Sebastian, A., Drechsler, U., Lantz, M., Despont, M., Jaroenapibal, P., Carpick, R.W., Chen, Y. and Sridharan, K. Ultra-low nanoscale wear through atom-by-atom attrition in silicon-containing diamond-like-carbon. Nature Nanotech. 5, 181-185 (2010).

3.            Liu, J., Grierson, D.S., Notbohm, J., Li, S., O’Connor, S.D., Turner, K.T., Carpick, R.W., Jaroenapibal, P., Sumant, A.V., Carlisle, J.A., Neelakantan, N. and Moldovan, N. Preventing nanoscale wear of atomic force microscopy through the use of monolithic ultrananocrystalline diamond probes. Small 6, 1140-1149 (2010).

4.            Jacobs, T.D., Gotsmann, B., Lantz, M.A. and Carpick, R.W. On the application of transition state theory to atomic-scale wear. Tribol. Lett. 39, 257 (2010).

5.            Jacobs, T.D.B. and Carpick, R.W. Nanoscale wear as a stress-assisted chemical reaction. Nature Nanotech. in press (2013).