Publication Date:
2016-01-29
Description:
A simple method was proposed to control the nanotribology behaviors of monocrystalline silicon against SiO 2 microsphere by adjusting relative humidity (RH). Experimental results indicated that adhesion work, friction coefficient, and nanowear of silicon against SiO 2 microsphere significantly varied between 60% and 90% RH. Under 60% RH, adhesion work was 119 mN/m, and friction coefficient was about 0.53. However, adhesion work and friction coefficient decreased to ∼70 mN/m and ∼0.3 under 90% RH, respectively. An apparent wear track ∼13 nm deep formed on the silicon surface under 60% RH, whereas no obvious wear scar was observed on the silicon surface under 90% RH. Analysis indicated that such tribological behaviors were due to different water condensations on the silicon surface under 60% and 90% RH. Under 60% RH, the water that condensed on the surfaces of the silicon sample and SiO 2 tip mainly consisted of ice-like water. As a result, adhesion work was enlarged by the breaking force of the ice-like water bridge in the contact area. Given that a ≡Si–O–Si≡ bonding bridge easily formed between the silicon surface and the SiO 2 tip with the help of water condensation under 60% RH instead of 90% RH, the friction coefficient was large and the nanowear of the silicon sample was severe under 60% RH. These results may help elucidate the nanotribology behaviors of silicon and facilitate the tribological design of dynamic microelectromechanical systems working under humid conditions.
Print ISSN:
0021-8979
Electronic ISSN:
1089-7550
Topics:
Physics
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