Organic molecule-metal interfaces are relevant both for theirtechnological applications and for the knowledge of the earlystage of the adsorption. In this context the interface propertiesplay an important role in determining the adsorbate orderingand its electronic properties. In this work we present theelectronic properties and the growth morphology of the CuPcmolecule grown on Al(100) and Au(110) surfaces. These twometals have completely di.erent properties that influence thenature of the interface. Al is a prototype of a free electronmetal and the CuPc/Al(100) interface is characterized by asignificant charge transfer as observed by the disappearanceof the HOMO-LUMO transition in the EELS spectra at lowcoverage [1]. Strong evidence of the interaction between themolecule and Al substrate also come from XPS [2] where weobserve the disappearance of the shake-up satellites in the C1s spectra and the complete reduction of copper for the lowestcoverages. On the contrary Au is characterized by a stronglocalization of d electrons and a low density of delocalized selectrons. For the CuPc/Au(110) interface we observe less important modification of the electronic structure of the moleculewith respect to the CuPc/Al(100) interface. Nonetheless theinteraction between the molecule and the Au substrate is notnegligible. In fact HR-UPS study has shown the presence ofinterface states [3]. From a morphological point of view weobserve that CuPc grown on Au(110) gives rise to di.erentsymmetry of the interface as a function of the CuPc thickness:the 1x2 clean Au reconstruction evolves in a 5x5 and in a 5x3reconstruction as observed by LEED. The Au(110) surface ismade by long channels of missing atoms that act as a guidefor the adsorption of the molecules. Along the direction of thechannels we observe a periodicity that match the dimension ofthe molecule, while along the other direction the x2 reconstructionof the Au atoms disappears after a deposition of a fractionof monolayer and it evolves in the x5 and the x3 reconstruction.As pointed out by GIXD [4], these reconstructions along the [001] direction is due to a rearrangement of the uppermostgold atoms. The CuPc/Al(100) interface does not show anylong range order. For the lowest coverage the strong interactionsuggests a flat lying deposition while for thicker film, XASdata indicate the growth of CuPc layer with the plane of themolecule perpendicular to the surface.
Ruocco, A., Evangelista, F., Stefani, G., Betti, M.G., Mariani, C., Cossaro, A., et al. (2004). The Copper-Phthalocyanine metal interface: electronic properties and growth morphology.
The Copper-Phthalocyanine metal interface: electronic properties and growth morphology
RUOCCO, Alessandro;EVANGELISTA, FABRIZIO;STEFANI, Giovanni;
2004-01-01
Abstract
Organic molecule-metal interfaces are relevant both for theirtechnological applications and for the knowledge of the earlystage of the adsorption. In this context the interface propertiesplay an important role in determining the adsorbate orderingand its electronic properties. In this work we present theelectronic properties and the growth morphology of the CuPcmolecule grown on Al(100) and Au(110) surfaces. These twometals have completely di.erent properties that influence thenature of the interface. Al is a prototype of a free electronmetal and the CuPc/Al(100) interface is characterized by asignificant charge transfer as observed by the disappearanceof the HOMO-LUMO transition in the EELS spectra at lowcoverage [1]. Strong evidence of the interaction between themolecule and Al substrate also come from XPS [2] where weobserve the disappearance of the shake-up satellites in the C1s spectra and the complete reduction of copper for the lowestcoverages. On the contrary Au is characterized by a stronglocalization of d electrons and a low density of delocalized selectrons. For the CuPc/Au(110) interface we observe less important modification of the electronic structure of the moleculewith respect to the CuPc/Al(100) interface. Nonetheless theinteraction between the molecule and the Au substrate is notnegligible. In fact HR-UPS study has shown the presence ofinterface states [3]. From a morphological point of view weobserve that CuPc grown on Au(110) gives rise to di.erentsymmetry of the interface as a function of the CuPc thickness:the 1x2 clean Au reconstruction evolves in a 5x5 and in a 5x3reconstruction as observed by LEED. The Au(110) surface ismade by long channels of missing atoms that act as a guidefor the adsorption of the molecules. Along the direction of thechannels we observe a periodicity that match the dimension ofthe molecule, while along the other direction the x2 reconstructionof the Au atoms disappears after a deposition of a fractionof monolayer and it evolves in the x5 and the x3 reconstruction.As pointed out by GIXD [4], these reconstructions along the [001] direction is due to a rearrangement of the uppermostgold atoms. The CuPc/Al(100) interface does not show anylong range order. For the lowest coverage the strong interactionsuggests a flat lying deposition while for thicker film, XASdata indicate the growth of CuPc layer with the plane of themolecule perpendicular to the surface.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
