  Unparalleled strength, chemical stability, ultimate surface-to-volume ratio
and excellent electronic properties of graphene make it an ideal candidate as a
material for membranes in micro- and nanoelectromechanical systems (MEMS and
NEMS). However, the integration of graphene into MEMS or NEMS devices and
suspended structures such as proof masses on graphene membranes raises several
technological challenges, including collapse and rupture of the graphene. We
have developed a robust route for realizing membranes made of double-layer CVD
graphene and suspending large silicon proof masses on membranes with high
yields. We have demonstrated the manufacture of square graphene membranes with
side lengths from 7 micro meter to 110 micro meter and suspended proof masses
consisting of solid silicon cubes that are from 5 micro meter multiply 5 micro
meter multiply 16.4 micro meter to 100 micro meter multiply 100 micro meter
multiply 16.4 micro meter in size. Our approach is compatible with wafer-scale
MEMS and semiconductor manufacturing technologies, and the manufacturing yields
of the graphene membranes with suspended proof masses were greater than 90%,
with more than 70% of the graphene membranes having more than 90% graphene area
without visible defects. The graphene membranes with suspended proof masses
were extremely robust and were able to withstand indentation forces from an
atomic force microscope (AFM) tip of up to ~7000 nN. The measured resonance
frequencies of the realized structures ranged from tens to hundreds of kHz,
with quality factors ranging from 63 to 148. The proposed approach for the
reliable and large-scale manufacture of graphene membranes with suspended proof
masses will enable the development and study of innovative NEMS devices with
new functionalities and improved performances.
