Abstract
Pentacene, an organic molecule, is a promising material for high-performance field effect transistors due to its high charge carrier mobility in comparison to usual semiconductors. However, the charge carrier mobility is strongly dependent on the molecular orientation of pentacene in the active layer of the device, which is hard to investigate using standard techniques in a real device. Raman scattering, on the other hand, is a high-resolution technique that is sensitive to the molecular orientation. In this work, we investigated the orientation distribution of pentacene molecules in actual transistor devices by polarization-dependent Raman spectroscopy and correlated these results with the performance of the device. This study can be utilized to understand the distribution of molecular orientation of pentacene in various electronic devices and thus would help in further improving their performances.
Highlights
Pentacene, an organic molecule, is a promising material for high-performance field effect transistors due to its high charge carrier mobility in comparison to usual semiconductors
If the pentacene molecules lie on the substrate, the radial polarization of incident light would result in minimum Raman intensity, while azimuthal polarization of incident light would show maximum Raman intensity of B3g mode
The information about molecular orientation of pentacene can be obtained from X-ray diffraction spectroscopy (XRD) technique, this technique has very low spatial resolution, which only gives an average value of orientation over a large area and it is not suitable for investigating the effect of molecular orientations on carrier mobility
Summary
An organic molecule, is a promising material for high-performance field effect transistors due to its high charge carrier mobility in comparison to usual semiconductors. The information about molecular orientation of pentacene can be obtained from X-ray diffraction spectroscopy (XRD) technique, this technique has very low spatial resolution, which only gives an average value of orientation over a large area and it is not suitable for investigating the effect of molecular orientations on carrier mobility This technique cannot be applied to study disordered part of the sample. We have investigated the orientation of pentacene molecules in actual transistor devices by utilizing polarization-dependent Raman spectroscopy and correlated these results with the performance of the device. In order to correlate the device performance with the presence of impurity molecules in a non-sublimated device as compared to a sublimated device, we quantitatively investigated the distributions of molecular orientation of pentacene molecules in both the devices using polarization-dependent Raman spectroscopy. Our analysis confirms that the pentacene molecules in the sublimated sample were aligned in wider areas in comparison with those in the non-sublimated device, and the sublimated device shows higher charge carrier mobility
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