In the last years a strong research effort has been devoted to build new devices based on nanostructured materials. One of the most interesting nanomaterial is carbon nanotube (CNT) which, thanks to its unique electronic and structural properties and to the possibility to be grown on different substrates, has been used for several applications, such as electronic devices and sensors. One of the most interesting applications is as nanostructured template to increase the surface area of organic and inorganic films deposited on them. For example the realization of new sensors for both gas and biological compounds is based of functionalized CNT. Another important research field is on organic films for the realization of several devices, such as transistors, sensors, solar cells, because of the possibility to synthesize an enormous amount of different organic compounds and to deposit them using low temperature and low cost techniques.
In this work we will present our recent results on the growth of copper phthalocyanine (CuPc) very thin films on multi-walled CNT (MWCNT). The MWCNT have been grown using CVD technique on silicon substrate and the CuPc films have been grown, by thermal evaporation, on the MWCNT in UHV conditions. We have studied the electronic properties of this system, as a function of the CuPc thickness, using soft XPS, to investigate the valence band features, and XPS to study the core levels. Moreover XRD and SEM techniques have been used to characterize the morphology and the crystalline structure of the system. The SEM images have shown the growth of CuPc particles around the MWCNT, which, looking at the XRD spectra, are nanocrystals in the â-form. The valence band spectra have shown a small shift of the CuPc HOMO peak for very small deposition and its maximum moves towards higher binding as the CuPc film thickness increases. The core levels do not show any sizeable variations indicating that the interaction between CuPc and MWCNT is very small. The effects on the HOMO position and the missing of any change in the core level peak can be explained in terms of variation of the growth mode of the molecules as the film thickness increases.
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