  We invented a method to fabricate graphene transistors on oxidized silicon
wafers without the need to transfer graphene layers. To stimulate the growth of
graphene layers on oxidized silicon a catalyst system of nanometer thin
aluminum/nickel double layer is used. This catalyst system is structured via
liftoff before the wafer enters the catalytic chemical vapor deposition (CCVD)
chamber. In the subsequent methane based growth process monolayer graphene
field-effect transistors (MoLGFETs) and bilayer graphene transistors (BiLGFETs)
are realized directly on oxidized silicon substrate, whereby the number of
stacked graphene layers is determined by the selected CCVD process parameters,
e.g. temperature and gas mixture. Subsequently, Raman spectroscopy is performed
within the channel region in between the catalytic areas and the Raman spectra
of fivelayer, bilayer and monolayer graphene confirm the existence of graphene
grown by this silicon-compatible, transfer-free and in-situ fabrication
approach. These graphene FETs will allow a simple and low-cost integration of
graphene devices for nanoelectronic applications in a hybrid silicon CMOS
environment.
