| The experimental method is used to study the properties of friction of the Si-DLC films in the paper. At the same time, the properties of elastic-plastic contact is analyzed as well as distributing rule of friction heat from the perspective of numerical simulation as Silicon MEMS devices before and after coated Si-DLC films.Firstly, this paper introduces the principle and specific process of two techniques which could manufacture Si-DLC films at the same time: electron cyclotron resonance plasma enhanced chemical vapor deposition and plasma enhanced unbalanced magnetron sputtering. The characterization of the prepared samples makes the Si-DLC film known as amorphous film. The AFM is used to make study on the surface properties. With negative substrate bias voltage increasing, the surface roughness decreases. When the bias sputtering is around 400V, there is a smooth surface morphology and a little adhesion force.Secondly, micron-level AFM of ball probe is used to do the friction test on Si-DLC films. The effect of plus load and scan rate on the frictional properties of film have been studied in the micrometer scale. Considered the impact of adhesion, the amendment Amonton formula is proposed for friction micro-characterization of low-load contact. The relationship between friction coefficient and surface asperity has been analyzed. According to the distribution of film surface asperity, a equivalent contact model of ball probe and film surface asperity is established in micrometer scale and gets the function expression f (p,Φ) of friction on the load parameters (p) and morphology parameters (Φ), which shows that contact with asperity density per unit area plays a dominant role on the size of the friction. The contact model successfully explains the phenomenon of friction test.In order to study the properties of friction of the Si-DLC film, the frictional experiments is done with tip probe, ball probe and flat probe. the mechanism of thin film adhesion and friction under contacts of different scales have been studied, In the light of the contact model which is built of probes and membrane surface asperity, the formula for surface adhesion and contacting area are derived which is indicated to play a leading role in the micro-contact. The micro-friction coefficient of tiny probe and film surface depends on the slope of the surface asperity but the height of asperity; contact asperity density per unit area decides on the ball probe friction of film surface; when the flat probe slide in the film surface, the friction depends on the applied load and surface morphology of micro-size effect on the friction is negligible.Finally, the finite element method is used to test the performance of elastic-plastic contact and distribution of friction heat of Silicon MEMS devices before and after coated Si-DLC films. The modeling process of the elastic-plastic contact and friction thermal analysis is built by ansys10.0 which considered the factors of establishing the geometric model of elastic-plastic contact and friction heat. It mainly analyzes the law between the parameters and contact properties and the distributing rule of friction heat and thermal coupling stress at elastic and elastic-plastic stages. The results show that: after the MEMS being coated with a layer of Si-DLC film, its resistance to external deformation and abrasion resistance are greatly improved, while the thermal coupling stress caused by friction heat reduces greatly.This paper has laid a good theoretical basis for studying micro-friction properties of DLC films and guiding the design and application of the MEMS.
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