Oligothiophenes are an interesting family of semiconducting pi-conjugated molecules, used to study the growth of poly-crystalline organic thin films and to fabricate high performance organic devices for several applications. The small size of such fundamental building blocks helps the investigation of their self assembly to understand the forces involved. This could permit to minimize the rise of different grains or domains inside the thin film. Such boundaries hinder different properties such as the charge carrier mobility inside the organic devices, decreasing their performances. Supersonic molecular beam deposition, the innovative technique we are using in the NanoScience Lab of IMEM, can achieve unprecedented results thanks to a much higher control on the deposition beam [ , ]. A proper setting of the source parameters allows to finely tune the molecules kinetic energy, the main factor affecting the way the molecules assembly on the substrate [ ]. In this contribution we relate on our investigations concerning the growth of ?-sexithiophene on silicon oxide substrate. We studied sexithiophene growth as a function of substrate temperature, substrate wettability and especially kinetic energy of the impinging molecules [ ]. Each of these parameters has a different effect on the growth of the molecular thin film, in particular on the size and shape of the sub-monolayer islands. Optimizing these parameters in order to obtain the largest islands and minimize the grain boundaries among them, we also deposited some thicker films which have been used to fabricate several arrays of organic field effect transistors. The better arrangement of the first monolayer drives in this case a quasi-layer-by-layer growth which produces wide, smooth and regular terraces. The wider islands and the lower grain boundary density lead to much better performance: a field effect mobility average value of 1.5o10-1 V?cm-1?s-1, twice higher than the best values in literature up to now. This work was financially supported by the Fondazione CARITRO Project "NanoSmart".
Supersonic Molecular Beam Deposition of ?-Sexithiophene: because energy matters!
M Tonezzer;
2012
Abstract
Oligothiophenes are an interesting family of semiconducting pi-conjugated molecules, used to study the growth of poly-crystalline organic thin films and to fabricate high performance organic devices for several applications. The small size of such fundamental building blocks helps the investigation of their self assembly to understand the forces involved. This could permit to minimize the rise of different grains or domains inside the thin film. Such boundaries hinder different properties such as the charge carrier mobility inside the organic devices, decreasing their performances. Supersonic molecular beam deposition, the innovative technique we are using in the NanoScience Lab of IMEM, can achieve unprecedented results thanks to a much higher control on the deposition beam [ , ]. A proper setting of the source parameters allows to finely tune the molecules kinetic energy, the main factor affecting the way the molecules assembly on the substrate [ ]. In this contribution we relate on our investigations concerning the growth of ?-sexithiophene on silicon oxide substrate. We studied sexithiophene growth as a function of substrate temperature, substrate wettability and especially kinetic energy of the impinging molecules [ ]. Each of these parameters has a different effect on the growth of the molecular thin film, in particular on the size and shape of the sub-monolayer islands. Optimizing these parameters in order to obtain the largest islands and minimize the grain boundaries among them, we also deposited some thicker films which have been used to fabricate several arrays of organic field effect transistors. The better arrangement of the first monolayer drives in this case a quasi-layer-by-layer growth which produces wide, smooth and regular terraces. The wider islands and the lower grain boundary density lead to much better performance: a field effect mobility average value of 1.5o10-1 V?cm-1?s-1, twice higher than the best values in literature up to now. This work was financially supported by the Fondazione CARITRO Project "NanoSmart".I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
