In this paper, we report on the in situ synthesis of graphene layers by means of chemical vapor deposition (CVD), directly on nickel micro-electromechanical systems (MEMS) surfaces. We have developed MEMS structures of which the temperature can be increased locally by Joule heating while in a methane environment. For our MEMS structures, the thermal time constant is 28 μs. As a result, we have control over the carbon precipitation time, thereby governing how many graphene layers are formed. Bi-layer to multi-layer graphene was observed using micro-Raman spectroscopy, but not single-layer graphene, as it gives no Raman signal when coupled on a nickel surface. The corresponding precipitation control theory is also presented in this paper, in which we relate the out-diffusion of carbon atoms from the grains of the nickel structure to the resulting number of graphene layers. Our method provides regulated carbon segregation from nickel and allows a prescribed number of graphene layers to form by tuning the precipitation time. In this way, we enable the direct in situ synthesis of graphene locally on the top and sidewalls of nickel MEMS structures, so that e.g. such graphene-coated MEMS surfaces can contribute towards a promising solution against friction and wear for MEMS devices with sliding components.

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In this paper, we report on the influence of capillary condensation on the sliding friction of sidewall surfaces in polycrystalline silicon micro-electromechanical systems (MEMS). We developed a polycrystalline silicon MEMS tribometer, which is a microscale test device with two components subject to sliding contact. One of the components can be heated in situ by Joule heating to set the temperature of the contact and thereby control the capillary kinetics at the MEMS sidewalls. We used an optical displacement measurement technique to record the stick–slip motion of the slider with sub-nanometer resolution, and we assessed the friction force with nanonewton resolution. All friction measurements were performed under controlled ambient conditions while sweeping the contact temperature from room temperature to 300 C, and from 300 C to room temperature. We were able to distinguish the two ways in which energy is dissipated during sliding: the ‘semi-statically’ dissipated energy attributed to asperity deformation and contact yield, and the dynamically dissipated energy ascribed to the release of the tension in the slider during slip events. We observed an increase in the dynamically dissipated energy at 80 C while sweeping down in temperature. This increase is caused by higher adhesion due to capillary condensation between the conformal surfaces. Our study highlights how energy is dissipated during the sliding contact of MEMS sidewalls, and it is helpful in overcoming friction in multi-asperity systems. @en

In this paper we present the characterization of the coefficient of thermal expansion (CTE) of in-situ doped polycrystalline SiC thin films, obtained by low pressure chemical vapor deposition (LPCVD). The material is characterized using V-beam actuators on which the temperature coefficient of resistance (TCR) and the in-plane displacement versus current are measured. A CTE value of 4.3 ± 0.4 ppm/K is obtained in the temperature region of 20°C to 300°C. This value is used in a finite element modeling (FEM) simulation of vertical SiC-SiO2 bimorph beams. For an actuator length of 700 μm, width of 100 μm and layer thickness of 2 μm, a displacement up to 200 μm can be obtained.@en

In this work, we have incorporated heaters in a MEMS device, which allow the in situ local heating of its contacting surfaces. This design offers a promising solution for MEMS devices with contacting components by preventing capillary-induced adhesion. The force of adhesion was assessed by optically measuring in-plane snap-off displacements. We were able to decrease adhesion from 500 nN to 200 nN with just one heated surface of which the temperature was set above 300 °C. The temperature should not be set too high: we observed increased adhesion due to a direct bonding process once the temperature was increased above 750 °C. Remarkably, adhesion increased by heating from room temperature to 75 °C, which is attributed to more water being transferred to the contact area due to faster kinetics. We observed the same effect in the cases where both surfaces were heated, although at slightly different temperatures. We demonstrated that heating only one surface to between 300 °C and 750 °C is sufficient to significantly lower adhesion, due to the removal of capillary menisci. The required heater is typically most easily implemented in a stationary part of the device.@en