Search

Using multi-step deposition mode, we developed an innovational strategy of homogenously multilayered (HM) structure to tailor the roughening kinetics of sputtered W films. Dynamic scaling analysis showed that all sublayers of HM W films exhibited the same anomalous roughening behavior, which originated from the limited surface diffusion. Intriguingly, different from its single-layered counterpart, the HM W films exhibited a suppression effect of kinetic roughening, which could be well manipulated by film modulation period. Detailed experimental characterization and phenomenological model analysis suggested that this roughening suppression arises from the multi-interruption of the continuous film roughening process, forming an interlayer interface after every interruption and restarting the sublayer roughening on the pre-sublayer surface. [ABSTRACT FROM AUTHOR]

Local disordering has been analyzed in ordered intermetallic CoAl films epitaxially grown on GaAs(001) substrates by molecular beam epitaxy. Transmission electron microscopy investigations demonstrate the appearance of the bcc phase in the CoAl epilayer, which is the disordered version of the B2 crystal lattice type. Variations in the growth temperature between 100 and 300 °C reveal that the degree of thermal disordering and the volume fraction of the disordered bcc phase increase with increasing temperature. Interface reactions were observed in the sample fabricated at 300 °C resulting in the formation of CoAs precipitates at the interface. These precipitates contribute to the plastic relaxation of the 1.2% lattice mismatch between the CoAl film and the GaAs substrate affecting the strain-induced order–disorder transition. The impact of disordering is discussed in connection to the high diffusivity of vacancies and Co atoms existing in the intermetallic alloy. [ABSTRACT FROM AUTHOR]

Single-crystal dendritic ZnO nanostructures in appearance of macroscale in mass production have been synthesized via the vapor-phase transport method with Cu catalyst at 930 °C. The hierarchical ZnO dendrites with a long central trunk and lots of multilevel branches are composed of well-oriented nanorods whose diameters range from 60 to 800 nm. Gas sensors based on as-synthesized ZnO products exhibit high sensitivity and selectivity to H2S gas at room temperature through detecting various gases. The large modulation of the energy barrier of contact between nanorods in ZnO dendrites by H2S gas at room temperature might be the origin of the high sensitivity. The results demonstrate that the ZnO dendrites, with macroscopical appearance and properties of nanomaterials, are potential to develop effective and high performance gas sensors. Moreover, the detailed humidity characteristics of the sensor have also been investigated in the relative humidity range of 5%-97.6%. [ABSTRACT FROM AUTHOR]

ZnGa2O4 nanowires were grown via a low-pressure chemical vapor deposition method, and the electrical transport properties of these nanowires were investigated. It was found that the current across individual nanowires was several picoamperes at a bias of 30 V, and the current was insensitive to oxygen and temperature. These behaviors still maintained as the ZnGa2O4 nanowires were exposed to below-band-gap irradiation. In contrast, upon exposure to 254 nm ultraviolet light, the current across the nanowire increased a lot. With decreasing oxygen pressure or increasing temperature, the photocurrent increased evidently; this could be understood from the Langmuir model and the adsorption isobar, respectively. The present results demonstrate that surface-related processes especially oxygen chemisorption have significant effects on the photoelectric properties of nanostructures. The optically driven oxygen and temperature sensing as found in the ZnGa2O4 nanowires may find promising applications in functional devices. [ABSTRACT FROM AUTHOR]

The effects of constant bias stress and electric field on the electromechanical behavior of <001>-oriented Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PMN–0.32PT) relaxor ferroelectric single crystals have been investigated. Both unipolar and bipolar responses are considered. Obtained results show that compressive bias stress with appropriate magnitude can significantly increase the piezoelectric constant. It is also found that bias electric field in the poling direction stabilizes the microstructure of PMN–0.32PT and reduces the hysteresis loss. The observed effects of bias stress and bias electric field on the electromechanical properties of <001>-oriented PMN–0.32PT single crystals can be interpreted in terms of phase-transformation-induced polarization rotation through intermediate phases. [ABSTRACT FROM AUTHOR]

The fabrication of single-crystal dendritic ZnO nanostructures via the vapor-phase transport method with Cu as catalyst at 930 degree Celsius is described. The ZnO dendrites with macroscopical appearance and nanomaterial properties could find potential use to develop effective and high performance gas sensors.