Tribology Letters

, Volume 15, Issue 3, pp 169–176 | Cite as

Tribological Properties of Self-Assembled Monolayers and Their Substrates Under Various Humid Environments



Using friction force microscopy (FFM) under controlled environments, we have systematically investigated the humidity effect on the frictional properties of two important classes of self-assembled monolayers (SAMs), i.e., N-octadecyltrimethoxysilane (OTE, CH3(CH2)17Si(OCH3)3) on SiO2(OTE/SiO2), and N-alkanethiols on Au(111), together with their respective substrates. Experimental results show that both OTE and alkylthiol SAMs can decrease the friction force between a Si3N4 atomic force microscope (AFM) tip and substrates. The nearly humidity-independent friction of the two kinds of SAMs indicates that these SAMs are ideal lubricants in applications of micro-electro-mechanical systems (MEMS) under different environments. The humidity dependence—as the humidity increases, the friction first increases and then decreases—of the two substrates, SiO2 and Au(111), can be explained by the adsorption of water. The decrease in the friction at high humidity is attributed to the low viscosity in the multilayers of water, while the increase in the friction at low humidity can be explained by the high viscosity between the water monolayer and the surfaces (AFM tip and sample), possibly due to the confinement effects. The effect of modification of the AFM tip with alkanethiol molecules on the humidity dependence of Au(111) friction has also been investigated.

humidity self-assembled monolayers (SAMs) atomic force microscope (AFM) 


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  1. [1]
    R. Maboudian, MRS Bulletin (1998) June, 47.Google Scholar
  2. [2]
    B. Bhushan and C. Dandavate, J. Appl. Phys. 87 (2000) 1201.Google Scholar
  3. [3]
    S. M. Spearing, Acta Mat. 48 (2000) 179.Google Scholar
  4. [4]
    S. Z. Wen and J. N. Ding, Chinese J. Mech Eng. 36 (2000) 39.Google Scholar
  5. [5]
    R. Maboudian and R. T. Howe, J. Vac. Sci. Technol. B 15 (1997) 1.Google Scholar
  6. [6]
    S. Z. Wen, Nanotribology (Tsinghua University Press, Beijing, 1998).Google Scholar
  7. [7]
    K. Komvopoulos, Wear 200 (1996) 305.Google Scholar
  8. [8]
    B. Bhushan, H. Liu, Phys. Rev. B 63 (2001) 245412.Google Scholar
  9. [9]
    A. Ulman, Introduction to Ultrathin Organic Films from Lang-muir-Blodgett to Self-Assembly (Academic Press, New York, 1991).Google Scholar
  10. [10]
    A. Ulman, Thin Films: Self-Assembled Monolayers of Thiols (Academic Press, New York, 1998).Google Scholar
  11. [11]
    V. DePalma and N. Tillman, Langmuir 5 (1989) 868.Google Scholar
  12. [12]
    H. Liu, S. I. U. Ahmed and M. Scherge, Thin Solid Films 381 (2001) 135.Google Scholar
  13. [13]
    X. D. Xiao, J. Hu, D. H. Charych and M. Salmeron, Langmuir 12 (1996) 235.Google Scholar
  14. [14]
    C. M. Mate, G. M. McClelland, R. Erlandsson and S. Chiang, Phys. Rev. Lett. 57 (1987) 1942.Google Scholar
  15. [15]
    A. Lio, D. H. Charych and M. Salmeron, J. Phys. Chem. B 101 (1997) 3800.Google Scholar
  16. [16]
    A. Lio, C. Morant, D. F. Ogletree and M. Salmeron, J. Phys. Chem. B 101 (1997) 4767.Google Scholar
  17. [17]
    M. Fujihira, D. Aoki, Y. Okabe, H. Takano, H. Hokari, J. Frommer, Y. Nagatani and F. Sakai, Chem. Lett. (1996) 499.Google Scholar
  18. [18]
    K. H. Cha and D. E. Kim, Wear 251 (2001) 1169.Google Scholar
  19. [19]
    M. Binggeli and C. M. Mate, Appl. Phys. Lett. 65 (1994) 415.Google Scholar
  20. [20]
    M. Binggeli and C. M. Mate, J. Vac. Sci. Technol. B 13 (1995) 1312.Google Scholar
  21. [21]
    T. Thundat, X. Y. Zheng, G. Y. Chen, R. J. Warmack, Surf. Sci., 294 (1993) L939.Google Scholar
  22. [22]
    R. D. Piner and C. A. Mirkin, Langmuir 13 (1997) 6864.Google Scholar
  23. [23]
    T. Sunada, T. Yasaka, M. Takakura, T. Sugiyawa, S. Miyazaki and M. Hirose, Jpn. J. Appl. Phys. 29 (1990) L2408.Google Scholar
  24. [24]
    C. R. Kessel and S. Granick, Langmuir 7 (1991) 532.Google Scholar
  25. [25]
    J. Hu, X. D. Xiao, D. F. Ogletree and M. Salmeron, Surf. Sci. 327 (1995) 358.Google Scholar
  26. [26]
    R. W. Carpick and M. Salmeron, Chem. Rev. 97 (1997) 1163.Google Scholar
  27. [27]
    D. F. Ogletree, R. W. Carpick and M. Salmeron, Rev. Sci. Instrum. 67 (1996) 3298.Google Scholar
  28. [28]
    L. M. Qian, X. D. Xiao and S. Z. Wen, Langmuir 16 (2000) 662.Google Scholar
  29. [29]
    A. Noy, D. V. Nezenov and C. M. Lieber, Ann. Rev. Mater. Sci. 27 (1997) 381.Google Scholar
  30. [30]
    X. D. Xiao and L. M. Qian, Langmuir 16 (2000) 8153.Google Scholar
  31. [31]
    H. Yoshizawa and J. N. Israelachvili, J. Phys. Chem. 97 (1993) 4128.Google Scholar
  32. [32]
    J. Hu, X. D. Xiao, D. F. Ogletree and M. Salmeron, Science 268 (1995) 267.Google Scholar
  33. [33]
    J. W. G. Tyrrell and P. Attard, Phys. Rev. Lett. 87 (2001) 176104.Google Scholar
  34. [34]
    Y. X. Zhu and S. Granick, Phys. Rev. Lett. 87 (2001) 096105.Google Scholar
  35. [35]
    Y. X. Zhu and S. Granick, Phys. Rev. Lett. 87 (2001) 096104.Google Scholar
  36. [36]
    J. N. Israelachvili, Fundamentals of Friction, eds. I. L. Singer and H. M. Pollock (Kluwer, Dordrecht, 1992) p. 351.Google Scholar
  37. [37]
    F. Tian, X. D. Xiao, M. M. T. Loy, C. Wang and C. L. Bai, Langmuir, 15 (1999) 24.Google Scholar

Copyright information

© Plenum Publishing Corporation 2003

Authors and Affiliations

  1. 1.Tribology Research InstituteSouthwest Jiaotong UniversityChengduP.R. China
  2. 2.Department of PhysicsThe Hong Kong University of Science and TechnologyHong KongChina

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