Electron transport measurements along molecules incorporating hexa-peri-hexabenzocoronenes (HBC) and organized in self assembled monolayers (SAM) are performed by using a junction based on an Au and a Hg electrode, Au-SAM//SAM-Hg. It is well known that HBC generates well ordered supramolecular aggregates via π-π interactions between the hexabenzocoronene discs. While charge mobilty across the supramolecular aggregates have been measured, there are no information of electron transfer along the axial axis of the aromatic core. This work focuses on i) the synthesis of a the soluble compound, 2-(5-[1,2]dithiolan-3-yl-pentanoic acid dodecyl ester)-5,8,11,14,17-(3,7-dimethyloctanyl) hexa-peri-hexabenzocoronene (HBC), that allows for organization in SAM, ii) the characterization of the HBC SAMs by by XPS, NEXFAS spectroscopy and elipsometry and, iii) I-V measurements across four junctions incorporating the HBC SAMs (HBCS) and SAMs formed by alkyl chains of different length (Cn): Au-Cn//C12-Hg, Au-HBCS//Cn-Hg, Au-Cn//HBCS-Hg, Au-HBCS//HBCS-Hg. The results show that i-V curves measured in Au-C18//C18-Hg, Au-HBCS//C18-Hg, Au-HBCS//HBCS-Hg are overlapping, indicating that the HBC core behaves as transparent to electrons in respect with the aliphatic anchoring chains. The aliphatic chains are responsible for the total tunneling barrier to electron transport of the HBC monolayers. The 30 Å thick HBC SAM can be considered as effectively composed of two parts: a ”highly conductive” HBC layer with a thickness of 10 Å and an “low conductive” aliphatic part with a thickness of 20 Å. Both high mechanical stability and high electric “conductivity” of the HBC unit, qualify this material as promising building block for molecular electronics.
Electron Transport through Hexa-peri-hexabenzocoronene Units in a Metal-SAMs-Metal Junction
DUATI, Marco;GRAVE, Christian;RAMPI, Maria Anita
2006
Abstract
Electron transport measurements along molecules incorporating hexa-peri-hexabenzocoronenes (HBC) and organized in self assembled monolayers (SAM) are performed by using a junction based on an Au and a Hg electrode, Au-SAM//SAM-Hg. It is well known that HBC generates well ordered supramolecular aggregates via π-π interactions between the hexabenzocoronene discs. While charge mobilty across the supramolecular aggregates have been measured, there are no information of electron transfer along the axial axis of the aromatic core. This work focuses on i) the synthesis of a the soluble compound, 2-(5-[1,2]dithiolan-3-yl-pentanoic acid dodecyl ester)-5,8,11,14,17-(3,7-dimethyloctanyl) hexa-peri-hexabenzocoronene (HBC), that allows for organization in SAM, ii) the characterization of the HBC SAMs by by XPS, NEXFAS spectroscopy and elipsometry and, iii) I-V measurements across four junctions incorporating the HBC SAMs (HBCS) and SAMs formed by alkyl chains of different length (Cn): Au-Cn//C12-Hg, Au-HBCS//Cn-Hg, Au-Cn//HBCS-Hg, Au-HBCS//HBCS-Hg. The results show that i-V curves measured in Au-C18//C18-Hg, Au-HBCS//C18-Hg, Au-HBCS//HBCS-Hg are overlapping, indicating that the HBC core behaves as transparent to electrons in respect with the aliphatic anchoring chains. The aliphatic chains are responsible for the total tunneling barrier to electron transport of the HBC monolayers. The 30 Å thick HBC SAM can be considered as effectively composed of two parts: a ”highly conductive” HBC layer with a thickness of 10 Å and an “low conductive” aliphatic part with a thickness of 20 Å. Both high mechanical stability and high electric “conductivity” of the HBC unit, qualify this material as promising building block for molecular electronics.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
