  We report low-temperature transport spectroscopy of a graphene quantum dot
fabricated by atomic force microscope nanolithography. The excellent spatial
resolution of the atomic force microscope allows us to reliably fabricate
quantum dots with short constrictions of less than 15 nm in length. Transport
measurements demonstrate that the device is dominated by a single quantum dot
over a wide gate range. The electron spin system of the quantum dot is
investigated by applying an in-plane magnetic field. The results are consistent
with a Lande g-factor of 2 but no regular spin filling sequence is observed,
most likely due to disorder.
