  We investigate electronic transport property of a graphene monolayer covered
by a graphene nanoribbon. We demonstrate that electronic transmission of a
monolayer can be reduced when covered by a nanoribbon. The transmission
reduction occurs at different energies determined by the width of nanoribbon.
We explain the transmission reduction by using interference between
wavefunctions in the monolayer and the nanoribbon. Furthermore, we show the
transmission reduction of a monolayer is combinable when covered by more than
one nanoribbon and propose a concept of "combination of control" for
nano-application design.
