13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- Figure 10. The tensile responses of different grafted alcohols on Si(111) surface. 5. Conclusion In this research, a bulk-fabricated side-wall Si-MEMS tribotester is fabricated to study the life-time and wear process in different gas environments. By using the on-chip buckle loading method and the resonant driving strategy, the early stage of wear can be studied and classified into adhesive and corrosive types, depending on the gas environment. Since the permitted wear is quite light in MEMS devices, introducing a suitable corrosive vapor, such as alcohol, can relieve the initial wear to prolong the life-time. For fatty alcohols, the thermal- and tribo- solvolysis may not give a full explanation of tribo-reactions. A mechanochemical mechanism is proposed to understand the possible degradation of grafted alcohols on silicon and fluoroalcohols exhibit much more stable than fatty alcohols in the DFT calculation. The average wear life-time ratio in 2,2,2-trifluoroethanol vapor is about 100 times larger than that in ethanol vapor, so trifluoroethanol can give an effective lubrication for silicon devices. Acknowledgements This work was supported by the National Natural Science Foundation of China with grant Nos. 91123033 and 51021064. References [1] K. Komvopoulos, Surface engineering and microtribology for microelectromechanical systems. Wear, 200 (1996) 305-327 [2] M.G. Hankins, P.J. Resnick, P.J. Clews, et al., Vapor deposition of amino-functionalized self-assembled monolayers on MEMS. Reliability, Testing, and Characterization of MEMS/MOEMS II, 4980 (2003) 238-247 [3] S.T. Patton, W.D. Cowan, K.C. Eapen, J.S. Zabinski, Effect of surface chemistry on the tribological performance of a MEMS electrostatic lateral output motor. Tribol Lett, 9 (2000) 199-209 [4] D.M. Tanner, J.A. Walraven, L.W. Irwin, M.T. Dugger, The effect of humidity on the reliability of a surface micromachined microengine. IEEE International Reliability Physics Symposium Proceedings, (1999) 189-197 [5] S.A. Henck, Lubrication of digital micromirror devicesTM, Tribol Lett, 3 (1997) 239-24 [6] D.B. Asay, M.T. Dugger, S.H. Kim, In-situ Vapor-Phase Lubrication of MEMS. Tribol Lett, 29 (2008) 67-74 [7] M.N. Gardos, Tribological behavior of polycrystalline and single-crystal silicon. Tribol Lett, 2 (1996) 355-373 [8] S.J. Timpe, D.H. Alsem, D.A. Hook, M.T. Dugger, K. Komvopoulos, Wear of polysilicon surface micromachines operated in high vacuum. J Microelectromech S, 18 (2009) 229-238 [9] S. Shen, Y. Meng, Adhesive and Corrosive Wear at Micro Scales in Different Vapor Environments, submitted to Friction. [10] J.F. Archard, Contact and rubbing of flat surfaces, J Appl Phys, 24 (1953) 981-988 [11] C. Mathew Mate, Tribology on the small scale, Oxford, 2008 [12] Y. Mo, K.T. Turner, I. Szlufarska, Friction laws at the nanoscale. Nature, 457 (2009) 1116-1119 [13] B. Gotsmann, M.A. Lantz, Atomistic wear in a single asperity sliding contact. Phys Rev Lett,
RkJQdWJsaXNoZXIy MjM0NDE=