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This letter investigates the effect of repeated bending of flexible p-channel low-temperature polycrystalline–silicon thin-film transistors employing an ultra-low-temperature process (

KTa1−xNbxO3 single crystals are typically regarded as normal ferroelectrics. Such crystals are thought to undergo a paraelectric-ferroelectric phase transition from the cubic to the tetragonal phase where generally a single hysteresis loop is expected. Nevertheless, a double-loop hysteresis is clearly observed in the tetragonal phase of KTa0.58Nb0.42O3. Our investigations reveal further that the double loop exhibits good ergodicity during changes in temperature under various applied electric fields. The origin of this unusual double-loop hysteresis in tetragonal KTa0.58Nb0.42O3 is revealed with the recoverable reorientation of the asymmetric polar domains.

The effect of hydrogenation on a 14 nm Co14Pd86/Al2O3(0001) thin film was investigated on the basis of the magnetooptical Kerr effect. After exposure to H2 gas, the squareness of the hysteresis loop showed a large transition from approximately 10% to 100% and the saturation Kerr signal was reduced to nearly 30% of the pristine value. The reversibility of the transition was verified and the response time was within 2–3 s. These observations indicate that the hydride formation transformed the short-range coupled and disordered magnetic state of the Co14Pd86 film to a long-range-ordered ferromagnetic state and induced appreciable decrease in the magnetic moment. The enhanced long-range-ordering and the reduction of the magnetic moment were attributed to the change of electronic structure in Co14Pd86 with hydrogen uptake.

We report interfacial characterization of 3,4,9,10-perylene-teracarboxylic dianhydride (PTCDA)-based organic spin valves (OSV) dusted with a thin layer of partially oxidized alumina at the organic semiconductor (OSC)/ferromagnet (FM) interfaces. Up to 13.5% magnetoresistance is achieved at room temperature. X-ray photoelectron spectroscopy measurements reveal interfacial electronic interaction between PTCDA and FM while the application of a thin alumina layer at the PTCDA/FM interfaces prevents the electronic hybridization and effectively preserves the spin injection into the OSC spacer. This finding demonstrates the critical effect of interfacial structure on magnetotransport behavior in OSV.

The perpendicular magnetic anisotropy(PMA) was shown to be established in ferromagnetic (FM)/fcc-Mn bilayers through the FM-antiferromagnetic (AFM) exchange coupling. We demonstrate here that such PMA can be further enhanced by incorporating an ultrathin Fe film as an underlayer. In a series of Fe/Mn bilayers, hysteresis loop measurement shows that the thickness of top Fe layer with PMA can be extended to a thicker range while an ultrathin Fe underlayer is inserted. Such enhancement of PMA is attributed to an increase of AFM ordering on the Mn film originated from the magnetic proximity effect with the Fe underlayer.

In perpendicularly magnetized Pd/Co/Pd trilayers, the hydrogenation not only increased Kerr signal but also significantly enhanced the magnetic coercivity (HC) by 17%. The reversibility was demonstrated by cyclic H2 exposure. The time constants of hydrogen absorption and desorption effect on HC range from tens to hundreds seconds, depending on the H2 gas pressure. The magneto-optical Kerr signal and magnetic coercivity was simultaneously recorded during H2 absorption and desorption. These multifarious signals respond differently and provide a detailed understanding of hydrogenation effect on the functional Pd/Co/Pd trilayers.

Photoresponsive organic field-effect transistors (PhotOFETs) based on palladium phthalocyanine (PdPc) and C60 were fabricated with different donor-acceptor layer sequences. Both planar heterojunction devices fabricated exhibit better performance under illumination than the single PdPc device. PhotOFETs with the structure SiO2/C60/PdPc/Au exhibit a higher photosensitivity and photoresponsivity than that with the structure SiO2/PdPc/C60/Au. The origin for this is largely the high mobility of C60 and the well-matched LUMO levels of PdPc and C60. The maximum photosensitivity of the SiO2/C60/PdPc/Au device is 8 × 103, and the photoresponsivity is approximately 28 times that of the single component PdPc device.

Pentacene organic phototransistors (OPTs) modified by introducing C60 electrodes buffer layer were fabricated. Compared with conventional single-layer pentacene OPTs, the devices with C60 buffer layer exhibited higher performance under illumination. Maximum photoresponsivity is 4.27 A/W at zero gate bias under 0.2 mW cm(-2), which is six times higher than that of single-layer device and exceeds that of most OPTs reported recently in the same conditions. The maximum photo/dark current ratio is also higher than 5 x 10(4). Meanwhile, the C60 modified device could obtain lower threshold voltage and higher field-effect mobility. These results suggest that single-layer OPTs modified by heterojunction buffer layer will obtain better optical response. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4756937]

Synchrotron x-ray scattering was used to study the evolution of interface roughness with annealing for a series of Cu thin films. The films were encapsulated in SiO2 or Ta/SiO2 and prepared by sputter deposition. Specular x-ray reflectivity was used to determine the root mean square roughness for both the upper and the lower Cu/SiO2 (or Cu/Ta) interfaces. The lateral roughness was studied by diffuse x-ray reflectivity. Annealing the films at 600 °C resulted in a smoothing of only the upper interface for the Cu/SiO2 samples, while the lower Cu/SiO2 interfaces and both interfaces for the Ta encapsulated films did not evolve significantly. This difference in kinetics is consistent with the lower diffusivity expected of Cu in a Cu/Ta interface (compared to a Cu/SiO2 interface) and the mechanical rigidity of the lower Cu/SiO2 interface. As a function of roughness wavelength, the upper Cu/SiO2 interfaces exhibited a roughness decay with annealing that was only 12.5% of that expected for classical capillarity driven smoothening of a free surface.

The modification of crystalline structure by epitaxial growth on different single crystals induces crucial effects on the exchange bias coupling. Due to the larger lattice constant (a0) of Cu3Au(100) (a0=3.75A), the vertical lattice constants of Fe∕FexMn1−x films on Cu3Au(100) are much smaller than those of the Fe∕FexMn1−x∕Cu(100) system (Cu: a0=3.61A). By reducing the vertical lattice constants, the interface exchange bias coupling energy of Fe∕FexMn1−x∕Cu3Au(100) is enhanced to be 0.12–0.18erg∕cm2, which is approximately four times that of the Cu(100) system.