The Research On Transport Properties Of Molecular Devices

In this paper, we present the recent development, main research methods,and theoretic basis in the molecular electronics field first. Then, we study the transport sensitivities of a carbon atomic wire attached, respectively, with seven kinds of commonly seen side-groups NO₂, CN, CHO, Br, C₆H₅, C₅H₄N, and NH₂. The intrinsic origins of side-group effects on the transport current in the wire are suppression of the transmission eigen-channel, change of the Mulliken population, diminution of the delocalization of HOMO or LUMO, and alternation of the resonant molecular orbital. We also use a small organic molecule to design a simple molecular switch and compute its voltage-current (I-V) curves. The analysis on the transmission spectrums, transmission coefficients in the two-dimensional Brillouin zone and the transmission eigenstate of each eigenchannel at the HOMO levels demonstrates that an obvious increase of delocalization of the atomic orbital induced by the rotation of a mid-benzene ring about the X or Y axis is the intrinsic origin of distinctive conducting switch behaviors. Meanwhile, such a switch has both explicitly stable state and meta-stable state that can be converted from each other by an energy stimulus or mechanical operations. These findings suggest that this small molecular switch has obvious potential advantages for scaling down a device to a possible ultra-small size. At last, we investigate the equilibrium conductance property of a simple resonant tunneling structure, comprised of benzene and cofacial cyclobutadiene, with a monatomic dopant in a two-probe system. The system displays distinctive metallic transport behavior with nonmetal dopants and has obvious advantages for tuning the transport properties of miniaturized molecular electronic applications. We also compared its difference in tunneling characteristics when it has atomic purity and at different sites of impurity. The result reveals that the site effect is very distinctive to the rectifier ratio and it can enhance, weaken or reverse the rectification behavior.