![]() The resulting stacked graphene sample is a freestanding film with near-perfect in-plane crystallinity but a mixed stacking order through the thickness, which separates it from all existing carbon materials. Heat-treatment of the sample up to 2800 ☌ results in the removal of interstitial contaminants and the healing of graphene layer defects. The graphene layers are transferred and stacked one by one using a wet process that leads to layer defects and interstitial contamination. ![]() « lessĪ macroscopic film (2.5 cm × 2.5 cm) made by layer-by-layer assembly of 100 single-layer polycrystalline graphene films is reported. A sacrificial layer can be applied to facilitate separation of a more » first carbon layer from a second carbon layer, wherein, upon pyrolysis to form the second carbon layer and lithography thereof, the sacrificial layer is removed to form a CMEMS comprising a first carbon layer (e.g., comprising bottom contacts) located beneath a second carbon layer (e.g., a mechanical layer). A pyrolyzed layer of carbon is lithographically defined after pyrolysis, wherein the post-pyrolysis etch process can produce carbon structures having repeatable and accurate device geometries, with straight sidewalls. The various embodiments can be utilized in producing a plurality of CMEMS with full production level fabrication, e.g., 6 inch wafers can be processed. The various technologies presented herein relate to formation of carbon micromechanical systems (CMEMS), wherein the CMEMS comprise multiple layers of carbon structures and are formed using a plurality of photoresist precursors that are processed to form carbon. Results of MEMS-based characterization were combined with the tribological and morphological properties measured by microscratch test and x-ray diffraction analysis. ![]() = films were assessed by using both mechanical characterization based on scanning profilometers and piezoresistive sensing elements integrated in the silicon cantilevers. The resistance was measured periodically and remained constant over 6 months' time. Thin film pyrolyzed carbon resistors were hermetically sealed in a nitrogen ambient in 24-pin dual in-line packages (DIP's). Thin level of disorder and the conductivity of thin film resistors were found to unchanged by 2Mrad gamma irradiation from a Co 60 source. The calculated average density of pyrolyzed AZ 4330 films was 1.32 g/cm 2. This was consistent with our Raman analysis, which also showed the film to more » be largely sp 2 bonded. Transmission electron microscopy (TEM) results showed the film to be largely amorphous, containing some sub-micrometer sized graphite crystallites. By fitting the results of self-heated bridges in an inert ambient, we calculated that the bridges survived to 1000C without failure. The temperature-dependent resistance was characterized from room temperature to 500C and found to be nearly linear over this range. Young's modulus of 23 GPa was extracted from nanoindentation measurements of pyrolyzed AZ 50XT films. Two novel multi-level, volume-scalable CMEMS processes were developed on 6" diameter wafers. ![]() By reactive ion etching pyrolyzed blanket AZ 50XT thick film photoresist, a high aspect ratio process was demonstrated with films >7.5um thick. By incorporating 2 wt.% graphene stiffeners into the film, a 65% increase in Young's modulus and 11% increase in conductivity were achieved. A novel method of increasing Young's modulus and the conductivity of pyrolyzed AZ 4330 was demonstrated by loading the films with graphene oxide prior to pyrolysis. ![]() In this work, we characterized the material and developed novel processes for fabricating carbon composite micro-electromechanical systems (CMEMS) structures. Pyrolyzed carbon as a mechanical material is promising for applications in harsh environments. ![]()
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