分子接面的電子傳輸與熱電效應

Abstract

我們研究分子接面的傳輸性質與熱電效應。以第一原理計算的方式，研究苯環胺基取代以及硝基取代兩種系統的電子輸運性質與熱電效應。我們藉著源漏電壓與閘極偏壓去調控其狀態密度，進而影響電子的輸運性質與熱電效應。我們發現有著不同官能基取代的苯環分子，其電子輸運性質與熱電效應的表現也不盡相同。官能基的取代可增加或減少□-orbital 的電子，導致導電性產生變化。胺基取代後的苯環分子接面會使□ -orbital 的電子減少，導致導電率下降。反之，硝基取代後的苯環分子接面會提供電子，在費米面附近產生新的能態，導致導電率上升。當我們觀察電子輸運性質與熱電效應時，因為相同原因，硝基系統易受源漏電壓與閘極偏壓的影響，其可調性較胺基系統為佳。

We investigate the electron transport and thermoelectric properties in amino-substituted (-NH2) and nitro-substituted (-NO) 1,4-benzenedithiolates molecular junctions by using first-principles approaches. We compare the density of states (DOSs) in the above systems by applying the source-drain biases and the gate voltages, which provide a means to control the electron transport and the thermoelectric properties. We find that the functional substitutions of 1,4-benzenedithiolates may donate or retrieve electrons from the □ -orbital, and thus have influence on the conductance of molecular junctions. The amino-substituted 1,4-benzenedithiolates molecular junctions withdraw electrons from□ -orbital, and suppresses the conductance. The nitro-substituted 1,4-benzenedithiolates molecular junctions donate electrons to □ -orbital and create states closer to the current-carrying window such that the conductance is enhanced. Consequently, the I-V characteristics and the Seebeck coefficients in NO-substituted 1,4-benzenedithiolates molecular junctions display richer features due to theses □ -donating states.