▎ 摘　　要

In this work we present a theoretical study of transport properties of a double crossbar junction composed of segments of graphene ribbons with different widths forming a graphene quantum dot structure. The systems are described by a single-band tight binding Hamiltonian and the Green's function formalism using real space renormalization techniques. We show calculations of the local density of states, linear conductance, and I-V characteristics. Our results depict a resonant behavior of the conductance in the quantum dot structures, which can be controlled by changing geometrical parameters such as the nanoribbon segment widths and the distance between them. By application of a gate voltage on determined regions of the structure, it is possible to modulate the transport response of the systems. We show that negative differential resistance can be obtained for low values of applied gate and bias voltages.