Organic semiconducting materials are attractive for their applicability to large-area flexible electronics because of their potential for achieving mechanical flexibility, low cost, and large-area fabrication [1]. The actual bottleneck for such kind of devices is at present their low charge carrier mobility, due to a high grain boundaries density in the thin film [2]. Deposition methods based on vacuum sublimation give the best results in terms of film quality, but still far from the desirable performance. The problem is the still limited ability to accurately control their growth, because this affects then structure, morphology and physical/chemical properties of the material, and thus lowers the performance of the electronic device. For these reasons a better control over molecular assembling during thin film growth will results in strong enhancement in devices properties. Supersonic Molecular Beam Deposition (SuMBD) has shown to be uniquely suitable to approach such challenge, achieving unprecedented control on morphology and structure [3]. This technique, based on supersonic beams made of organics seeded in lighter carrier gasses, permits to overcome some thermodynamic limitations and opens new perspectives in realizing structures controlled at different length scales [4]. Here we report the results achieved growing sexithiophene (?-6T) sub-monolayer films by SuMBD. The possibility to control the energetic properties of the precursor permits indeed to realize highly ordered thin films. We show the morphological (AFM) evolution of the sub-monolayer molecular islands as a function of the growth conditions, showing the high quality of the films deposited by SuMBD. Furthermore we report the electrical characterization of field effect transistors realized with thicker ?-6T films, showing greatly enhanced electrical properties with a carrier mobility of 0.15 cm2/V?s, to our knowledge the best values found in literature for this materials. This opens new perspective for the application of such compounds in sensing or photovoltaic where relative high mobility are request.
SuMBD growth of ?-sexithiophene thin films: influence of kinetic energy on sub-monolayer formation and device performance
M Tonezzer;
2010
Abstract
Organic semiconducting materials are attractive for their applicability to large-area flexible electronics because of their potential for achieving mechanical flexibility, low cost, and large-area fabrication [1]. The actual bottleneck for such kind of devices is at present their low charge carrier mobility, due to a high grain boundaries density in the thin film [2]. Deposition methods based on vacuum sublimation give the best results in terms of film quality, but still far from the desirable performance. The problem is the still limited ability to accurately control their growth, because this affects then structure, morphology and physical/chemical properties of the material, and thus lowers the performance of the electronic device. For these reasons a better control over molecular assembling during thin film growth will results in strong enhancement in devices properties. Supersonic Molecular Beam Deposition (SuMBD) has shown to be uniquely suitable to approach such challenge, achieving unprecedented control on morphology and structure [3]. This technique, based on supersonic beams made of organics seeded in lighter carrier gasses, permits to overcome some thermodynamic limitations and opens new perspectives in realizing structures controlled at different length scales [4]. Here we report the results achieved growing sexithiophene (?-6T) sub-monolayer films by SuMBD. The possibility to control the energetic properties of the precursor permits indeed to realize highly ordered thin films. We show the morphological (AFM) evolution of the sub-monolayer molecular islands as a function of the growth conditions, showing the high quality of the films deposited by SuMBD. Furthermore we report the electrical characterization of field effect transistors realized with thicker ?-6T films, showing greatly enhanced electrical properties with a carrier mobility of 0.15 cm2/V?s, to our knowledge the best values found in literature for this materials. This opens new perspective for the application of such compounds in sensing or photovoltaic where relative high mobility are request.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
