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We have grown In{sub x}Ga{sub 1-x}N/GaN quantum wells atop GaN microdisk with {gamma}-LiAlO{sub 2} substrate by using plasma-assisted molecular beam epitaxy. The structural and optical properties of the samples were analyzed by transmission electron microscopy, x-ray diffraction, cathodoluminescence, and photoluminescence measurements. Based on the measured results, we obtained the indium concentration of the In{sub x}Ga{sub 1-x}N/GaN single quantum well to be x = 0.25 with a band-gap energy of 2.31 eV, which is consistent with the bowing effect of bulk In{sub x}Ga{sub 1-x}N: E{sub g}(x) = [3.42 - x * 2.65 - x * (1 - x) * 2.4] eV.

Wurtzite/zinc-blende/wurtzite GaN heterophased quantum wells (QWs) were grown by plasma-assisted molecular beam epitaxy. A self-assembling mechanism was used to simulate the heterophased QW, in which a wurtzite/zinc-blende phase transition was created by rotating the threefold symmetric N-Ga vertical bond 60°. The GaN heterophased QW was attested by transmission electron microscopy, selective area electron diffraction and cathodoluminescence measurements.

Extremely high oxygen sensing is realized from individual ZnSnO3 nanowires with abundant grain boundaries. The current across one single ZnSnO3 nanowire increases by about six orders of magnitude, from 1.20×10−7to3.78×10−1μA, as the oxygen pressure decreases from 3.7×104to1.0×10−4Pa. Such a drastic sensing is ascribed to grain boundary barrier modulation. This interpretation is confirmed by the sensing experiments under UV illumination. The results demonstrate a promising approach to realize miniaturized and highly sensitive oxygen sensors.

Extremely stable electric field emission from well-aligned AlZnO nanowire arrays is realized. The emission current density is up to 6.5mA∕cm2, and no current saturation is observed. The turn-on field is 2.9V∕μm as d (distance between the nanowire emitters and anode) is 0.64mm. After aging for two days, the emission current is extremely stable with the fluctuations of±0.4%. The high stability arises from the high crystal quality with few surface states of the nanowires and the in situ fabrication of cathodes. The field emission behaviors are in excellent agreement with Fowler–Nordheim theory, and the relationship between the field enhancement factor β and d follows a universal equation. Our results imply that AlZnO nanowire arrays are promising candidates for field emission displays.

V2O4∙0.25H2O nanowires are synthesized via hydrothermal route. The nanowires are of metastable phase, and transverse grain boundaries are observed in their microstructures. Transport through individual V2O4∙0.25H2O nanowires shows nonlinear current-voltage (I-V) characteristics in the bias range of −3to3V. The resistance rapidly decreases from 2.54to0.5MΩ as the bias is raised from 0to1V. Such behaviors can be attributed to the presence of the barrier at the transverse grain boundary. By analyzing the I-V curves at various temperatures, the effective barrier height is estimated to be about 0.13eV. Our results provide important information about how the microstructure mismatch affects the electrical properties.

Several kinds of In2O3 nanowires (NWs) with different shapes and diameters were in situ synthesized from indium films with different thicknesses at a low temperature of 400°C. The NWs had screw structures, and they grew along each axial screw direction by vapor-solid growth mechanism. The thin NWs were synthesized with low indium vapor supersaturation. Two-dimensional nucleation and radial growth trends occurred when the supersaturation increased. The field emission results showed that the turn-on and threshold fields of the thick conical In2O3 NWs were lower than those of the thin ones.

Composite ZnSnO3 nanowires are synthesized via a one-step thermal evaporation method. The nanowires are of core-shell structures with the presence of grain boundary and out-of-phase boundaries. Transport through individual nanowires shows nonlinear current-voltage (I-V) characteristics in the range of the voltage from −3to3V. Such a behavior can be attributed to the presence of the barrier at the grain boundary, and the effective barrier height is estimated to be about 0.22eV by analyzing the I-V curves at various temperatures. The current at −3V jumps from 0.12to6.0μA within 30s at 300K as exposed to UV illumination. Such jump can be well explained in terms of effective barrier height and depletion width.

The SnO2 nanorods with a diameter down to 3nm are synthesized through a hydrothermal route and their sensing properties are investigated. The small size is confirmed by the results of x-ray diffraction, transmission electron microscope and Raman scattering spectrum. The sensitivity is up to 83.8 as the nanorod sensor is exposed to 300ppm ethanol vapor in air. Moreover, the linear dependence of the sensitivity on the ethanol concentration is observed for each of the 20 sensors. Compared with the measured results of 80–180nm tin oxide particles, such linear dependence is related to the small size effect.

In a basic water-alcohol mixing solution without any other toxically organic solvents, the single crystalline SnO2 nanorods with diameters of 4–15 nm and lengths of 100–200 nm were synthesized using SnCl4 as a precursor. The sensors fabricated from the nanorods exhibited the sensitivity of 31.4 for 300 ppm of ethanol. Both the response and recovery time are short, around 1 s. Moreover, a linear dependence of the sensitivity on the ethanol concentration was observed. These behaviors were well explained by considering the high surface-to-volume ratio of the nanorods.