Negative differential resistance in a hybrid silicon-molecular system: resonance between the intrinsic surface-states and the molecular orbital.
It has been a long-term desire to fabricate hybrid silicon-molecular devices by taking advantages of organic molecules and the existing silicon-based technology. However, one of the challenging tasks is to design applicable functions on the basis of the intrinsic properties of the molecules, as well as the silicon substrates. Here we demonstrate a silicon-molecular system that produces negative differential resistance (NDR) by making use of the well-defined intrinsic surface-states of the Si (111)-√3 × √3-Ag (R3-Ag/Si) surface and the molecular orbital of cobalt(II)-phthalocyanine (CoPc) molecules. From our experimental results obtained using scanning tunneling microscopy/spectroscopy, we find that NDR robustly appears at the Co(2+) ion centers of the CoPc molecules, independent of the adsorption configuration of the CoPc molecules and irrespective of doping type and doping concentration of the silicon substrates. Joint with first principle calculations, we conclude that NDR is originated from the resonance between the intrinsic surface-state band S(1) of the R3-Ag/Si surface and the localized unoccupied Co(2+)d(z(2)) orbital of the adsorbed CoPc molecules. We expect that such a mechanism can be generally used in other silicon-molecular systems.
Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China.
Weihua
W
Wang
Yongfei
Y
Ji
Hui
H
Zhang
Aidi
A
Zhao
Bing
B
Wang
Jinlong
J
Yang
J G
JG
Hou
D003198:Computer Simulation; D017097:Electric Impedance; D008422:Materials Testing; D008956:Models, Chemical; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties
D012825:Silicon