Control and prediction of crystal structures of molecular semiconductors are considered challenging, yet they are crucial for rational design of superior molecular semiconductors. It is here reported that through methylthiolation, one can rationally control the crystal structure of pyrene derivatives as molecular semiconductors; 1,6‐bis(methylthio)pyrene keeps a similar sandwich herringbone structure to that of parent pyrene, whereas 1,3,6,8‐tetrakis(methylthio)pyrene (MT‐pyrene) takes a new type of brickwork structure. Such changes in these crystal structures are explained by the alteration of intermolecular interactions that are efficiently controlled by methylthiolation. Single crystals of MT‐pyrene are evaluated as the active semiconducting material in single‐crystal field‐effect transistors (SC‐FETs), which show extremely high mobility (32 cm2 V−1 s−1 on average) operating at the drain and gate voltages of −5 V. Moreover, the band‐like transport and very low trap density are experimentally confirmed for the MT‐pyrene SC‐FETs, testifying that the MT‐pyrene is among the best molecular semiconductors for the SC‐FET devices.

The driving mechanism of the metal-insulator transition (MIT) in VO(2) has always attracted attention, in particular with regards to understanding if and how the doping mechanism may tune the MIT transition temperature. However, due to the lack of detailed local structural information, in this oxide the underlying MIT mechanism is still matter of debate. In this contribution on the V(1-x)W(x)O(2) system, we attempt to clarify the origin of the MIT induced by tungsten doping. Combining W L(3)-edge and V K-edge extended X-ray absorption fine-structure (EXAFS) spectroscopy, the local structures around both V and W have been obtained. The data point out the occurrence of internal stress along the V-V chains induced by doping. It reaches a critical value that remains constant during the transition. The main effect of the internal stress on the vanadium local structure has also been identified. Actually, upon increasing the dopant concentration, the tilt of the V-V pairs towards the apex oxygen atoms in the VO(6) octahedron decreases while the V-V bond lengths remain unchanged. The electronic structure has also been investigated by O K-edge X-ray absorption near-edge structure (XANES) spectroscopy. Actually, at high doping concentrations the interaction of O(2p) and the V d(∥) state increases, while the hybridization of O(2p) and V π* decreases. The O(2p)-V(3d) hybridization is therefore an essential parameter correlated with the decreasing transition temperature in the V(1-x)W(x)O(2) system.

High performance, air stable and solution-processed small molecule 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C 8 -BTBT) based organic field-effect transistors (OFETs) with various electrode configurations were studied in detail. The contact resistance of OFET devices with Ag, Au, WO 3 /Ag, MoO 3 /Ag, WO 3 /Au, and MoO 3 /Au were compared. Reduced contact resistance and consequently improved performance were observed in OFET devices with oxide interlayers compared to the devices with bare metal electrodes. The best oxide/metal combination was determined. The possible mechanisms for enhanced electrical properties were explained by favorable morphological and electronic structure of organic/metal oxide/metal interfaces.

We report the crystal structure and magnetic properties of Al1−xNixN films with 0 ≤ x ≤ 0.032 deposited on Si (100) substrates by radio frequency reactive sputtering. X-ray diffractometry, x-ray photoemission spectroscopy, and x-ray absorption fine structure analysis clearly showed that Ni atoms were successfully incorporated into AlN, while the crystal structure of the films was maintained. All the doped samples exhibited ferromagnetism both at 5 K and 300 K. The saturation magnetizations (Ms) and coercive fields (Hc) tended to decrease as Ni concentration increased from 0.019 to 0.032, the maximum Ms obtained at 5 K and 300 K were about 0.025 and 0.014 emu/g, respectively, and the corresponding Hc were 208 and 60 Oe. Temperature dependence of remanent magnetization showed that the ferromagnetic transition temperature was beyond 300 K.

Multiple functionality of tungsten polyoxometalate (POM) has been achieved applying it as interfacial layer for solution processed high performance In2O3 thin film transistors, which results in overall improvement of device performance. This approach not only reduces off-current of the device by more than two orders of magnitude, but also leads to a threshold voltage reduction, as well as significantly enhances the mobility through facilitated charge injection from the electrode to the active layer. Such a mechanism has been elucidated through morphological and spectroscopic studies.

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