The Electronic Transport Properties Of Novel Low-dimensional Carbon Allotropes

In recent decades, the carbon-based nano-materials had attracted much attentions.After the fullerene and carbon nanotubes, more low-dimensional carbon allotropeshave been synthesized successfully, such as graphene and graphyne. These carbonallotropes possess different electronic properties. Therefore, much attentions has beenfocused on this filed—novel low-dimensional carbon allotropes. In this thesis, usingfirst-principles calculations and green’s function methods, the transport properties ofsome low-dimensional carbon allotropes are studied.In chapter one, the research background of single-layer carbon nanomaterials,espeically the electronic properties of graphene and graphyne are introduced.In chapter two, the first-principles calculations and green’s function methods andrelated computing software are introduced.In chapter three, we have investigated the transport properties of graphenequantum dots (GQDs)/graphyne quantum dots (GYQDs) systems. It is found that theresonant transmissions are induced by the quasi-bound states confined in the QDs,thus the current-voltage characteristics of these QD systems which exhibit severalrepresentative peaks of multiple negative differential resistance (NDR) behaviors. Theresonant peaks and NDR behaviors can be tuned by the size of QDs. As the size ofQDs increases, the number of resonant peaks increases and shift to the Fermi level,this results in NDR behaviors that appeared at lower bias. In addition, comparing thetwo carbon-based QD systems, GYQD systems possess more amazing electronictransport properties for more robust resonant transmission and NDR behaviorappeared at lower bias. These results could provide useful applications based on thegraphene or graphyne quantum dots in electronics.In chapter four, we have studied the transport properties of a novel two-dimensional carbon allotrope, named3,12-graphene. We find that the3,12-grapheneexhibits interesting properties, i.e., the flat band near Fermi energy mainly contributedby the pzorbital. The armchair-edged3,12-graphene nanoribbons are semiconductor,and the band gap can be tuned by the width of nanoribbons. The two typeszigzag-edged of3,12-graphene nanoribbons remain the metal properties. A nearly atband appears around the Fermi level are ruled by the electronic states confined at thecenter of the nanoribbons. These interesting ndings could offer useful guidelines for the design of electronics.In the fifth chapter, a summary of this thesis is given and we explicitly describethe conception of future studies.