Electronic transport of SiC molecular chains in parallel via first-principles calculations

Abstract

Motivated by the trend of increasing miniaturization and multifunctional implementation, the electronic transport properties of two silicon carbide (SiC) molecular chains in parallel sandwiched between two semi-infinite Au(100)-3 × 6 electrodes are investigated using the density-functional theory and nonequilibrium Green's function formalism. The π-bonding molecular orbitals resulting from the in-phase combination of two px or py atomic orbitals of the C and Si atoms are found to play a key role in the electronic transport, and the possible electron pathways are summarized. Our results show that changing the separation between the two chains in a certain range can produce remarkable differences in transport properties. When the two chains are in small separation (d = 2.884 Å), their strong electrostatic interaction makes a constructive contribution to the electronic transport properties, in which the underlying physical mechanism has been revealed. We also find that d = 5.768 Å is the critical distance both for the transport difference and for the electrostatic interaction in the top-top configuration. Both the conductance (classical Kirchhoff's superposition law) and the current follow the superposition law well in the atomic scale when d = 5.768 Å, much smaller than the critical distance of 15.5 Å from the result of Zhou et al. [Carbon 95, 503 (2015)]. Additionally, the superposition law is more valid for a larger chain spacing (d ≥ 5.768 Å). Our work demonstrates that the realization of the superposition law and the way of increasing current and rectification effect may lay the foundation for the miniaturization exploration and multifunctional implementation of SiC chain related molecular devices.