  Variability effects in graphene can result from the surrounding environment
and the graphene material itself, which form a critical issue in examining the
feasibility of graphene devices for large-scale production. From the
reliability and yield perspective, these variabilities cause fluctuations in
the device performance, which should be minimized via device engineering. From
the metrology perspective, however, the variability effects can function as
novel probing mechanisms, in which the 'signal fluctuations' can be useful for
potential sensing applications. This paper presents an overview of the
variability effects in graphene, with emphasis on their challenges and
opportunities for device engineering and applications. The discussion can
extend to other thin-film, nanowire and nanotube devices with similar
variability issues, forming general interest in evaluating the promise of
emerging technologies.
