Interfacial States and Fano-Feshbach Resonance in Graphene-Silicon Vertical Junction

Interfacial quantum states are drawing tremendous attention recently, because of their importance in design of low-dimensional quantum hetero-structures with desired charge, spin or topological properties. Although most of studies of the interfacial exchange interactions mainly performed across the interface vertically, the lateral transport nowadays is still a major experimental method to probe these interactions indirectly. In this report, we fabricated a graphene and hydrogen passivated silicon interface to study the interfacial exchange processes. For the first time we found and confirmed a novel interfacial quantum state, which is specific to the 2D-3D interface. The vertically propagating electrons from silicon to graphene results in electron oscillation states at the 2D-3D interface. A harmonic oscillator model is used to explain this interfacial state. In addition, the interaction between this interfacial state (discrete energy spectrum) and the lateral band structure of graphene (continuous energy spectrum) result in Fano-Feshbach resonance. Our results show that the conventional description of interfacial interaction in low-dimensional systems is valid only in considering the lateral band structure and its density-of-states and is incomplete for the ease of vertical transport. Our experimental observation and theoretical explanation provide more insightful understanding on various interfacial effects in low-dimensional materials, such as proximity effect, quantum tunneling, etc. More important, the Fano-Feshbach resonance may be used to realize all solid-state and scalable quantum interferometer.