▎ 摘　　要

We report on magneto-transport measurements on low-density, large-area monolayer epitaxial graphene devices grown on SiC. We observe temperature (T)-independent crossing points in the longitudinal resistivity rho(xx,) which are signatures of the insulator-quantumHall (I-QH) transition, in all three devices. Upon converting the raw data into longitudinal and Hall conductivities sigma(xx) and s sigma(xy), in the most disordered device, we observed a T-driven flow diagram approximated by the semi-circle law as well as the T-independent point in sigma(xy) near e(2)/h. We discuss our experimental results in the context of the evolution of the zero-energy Landau level at lowmagnetic fields B. We also compare the observed strongly insulating behaviour withmetallic behaviour and the absence of the I-QH transition in graphene on SiO2 prepared by mechanical exfoliation.