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We report on the optical and structural characterization of rubrene polycrystalline films fabricated from vacuum deposition with various substrate temperatures (Tsub). Depending on Tsub, the role of twisted and planar rubrene conformational isomers on the properties of rubrene films is focused. The temperature (T)-dependent inverse optical transmission (IOT) and photoluminescence (PL) spectra were performed on these rubrene films. The origins of these IOT and PL peaks are explained in terms of the features from twisted and planar rubrene molecules and of the band characteristics from rubrene molecular solid films. Here, two rarely reported weak-peaks at 2.431 and 2.605 eV were observed from IOT spectra, which are associated with planar rubrene. Besides, the T-dependence of optical bandgap deduced from IOT spectra is discussed with respect to Tsub. Together with IOT and PL spectra, for Tsub > 170 °C, the changes in surface morphology and unit cell volume were observed for the first time, and are attributed to the isomeric transformation from twisted to planar rubrenes during the deposition processes. Furthermore, a unified schematic diagram in terms of Frenkel exciton recombination is suggested to explain the origins of the dominant PL peaks performed on these rubrene films at 15 K.

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We demonstrate high-performance Schottky CMOS transistors with NiSi source/drain and gate-all-around (GAA) silicon nanowire (∼5 nm) channels. The transistors exhibit good I on /I off characteristics, along with fully controlled shortchannel effects revealed by low drain-induced barrier lowering (∼10 mV/V) and near-ideal subthreshold swing (∼60 mV/dec). Although the N-MOSFET required dopant segregation to suppress the ambipolar behavior, excellent P-MOSFET characteristics could be achieved without the use of barrier modification techniques. We attribute this to the Schottky barrier thinning in a nanosized metal-semiconductor junction and superior gate electrostatic control in a GAA nanowire architecture.