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The performance of metal-insulator-semiconductor (MIS) type tunneling diodes based on ZnO nanostructures is investigated through modeling. The framework used in this work is the Schrödinger equation with an effective-mass approximation. The working mechanism of the MIS type tunneling diode is investigated by examining the electron density, electric field, electrostatic potential, and conduction band edge of the device. We show that a valley in the electrostatic potential is formed at the ZnO/MgO interface, which induces an energy barrier at the ZnO side of this interface. Therefore, electrons need to overcome two barriers: the high and narrow MgO barrier, and the barrier from the depletion region induced at the ZnO side of the ZnO/MgO interface. As the MgO layer becomes thicker, the valley in electrostatic potential becomes deeper. At the same time, the barrier induced at the ZnO/MgO interface becomes higher and wider. This leads to a fast decrease in the current passing through the MIS diode. We optimize the thickness of the MgO insulating layer, sandwiched between a ZnO film (in this work we use a single ZnO nanowire) and a metal contact, to achieve maximum performance of the diode, in terms of rectification ratio. An optimal MgO layer thickness of 1.5 nm is found to yield the highest rectification ratio, of approximately 169 times that of a conventional metal-semiconductor-metal Schottky diode. These simulated results can be useful in the design and optimization of ZnO nanodevices, such as light emitting diodes and UV photodetectors. [ABSTRACT FROM AUTHOR]

We developed and demonstrated a ZnO/ZnS/Au composite photoanode with significantly enhanced photoelectrochemical water-splitting performance, containing a ZnS interlayer and Au nanoparticles. The solar-to-hydrogen conversion efficiency of this ZnO/ZnS/Au heterostructure reached 0.21%, 3.5 times that of pristine ZnO. The comparison of the incident photon-to-current efficiency (IPCE) and the photoresponse in the white and visible light regions further verified that the enhancement resulted from contributions of both UV and visible light. The modification of the Au NPs was shown to improve the photoelectrochemical (PEC) performance to both UV and visible light, as modification encouraged effective surface passivation and surface-plasmonresonance effects. The ZnS interlayer favored the movement of photogenerated electrons under UV light and hot electrons under visible light, causing their injection into ZnO; this simultaneously suppressed the electron-hole recombination at the photoanode-electrolyte interface. The optimized design of the interlayer within plasmonic metal/semiconductor composite systems, as reported here, provided a facile and compatible photoelectrode configuration, enhancing the utilization efficiency of incident light for photoelectrochemical applications. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The piezoelectric properties of [0001]-oriented ZnO nanowires are investigated via density functional theory (DFT). The axial effective piezoelectric coefficient of ZnO nanowires is significantly greater than the bulk value, and the coefficient increases as the nanowire size decreases. It is proved that the enhancement comes from both the reduction of volume per Zn-O pair and the enhancement of the Poisson's ratio. Further study shows that the macroscopic polarization behavior of ZnO nanowires is determined by the crystal structure parameters and the ratio of surface atoms, and an analytic expression is obtained. This work provides a deeper understanding of the size effects of the piezoelectricity of ZnO nanowires and sheds some light on the confusion reported on this subject. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Uniform ZnO normal nanobelts and toothed-nanobelts have been successfully synthesized respectively through pure zinc powder evaporation without catalyst at 600°C. Experimental results indicate that the key to the fabricating method is to control the gas flow rates and the partial pressures of argon, oxygen and zinc vapor. Scanning electron microscopy and high-resolution transmission electron microscopy observations show that the ZnO nanobelts have several types of single crystalline morphology. HRTEM images reveal that there are numerous screw dislocations and the growth is around the dislocations in the toothed-nanobelts. The growth of ZnO nanobelts is controlled by vapor-solid and screw dislocation mechanisms. Room temperature photoluminescence spectra of the toothed-nanobelts showed a UV emission at ∼390 nm and a broad green emission with 4 subordinate peaks at 455–495 nm. [ABSTRACT FROM AUTHOR]

200 nm Fe-N thin films deposited on glass substrates by RF sputtering were vacuum annealed at 250–350C under 12000 A/m magnetic field. Heat treatment was effective in improving the soft magnetic properties of the Fe-N film. When the nitrogen content was in the range of 5–7 at. %, the thin films consisted of α′ + α″ after heat treatment and had excellent soft magnetic properties of 4π M s = 2.4 T, H c < 80 A/m, μ r = 1500 under 2–10 MHz. The properties of the films meet the needs of a write head material used in the dual element GMR/inductive heads. The fromation mechanism and lattice constants of the a’ phase in Fe-N thin film are different from Jack’s results obtained from y-a 1 transformation in bulk samples. The linear relationship between a, c and C for thin film was obtained as [ABSTRACT FROM AUTHOR]

C3N4 films have been synthesized on both Si and Ft substrates by microwave plasma chemical vapor deposition (MPCVD) method. X-ray spectra were calculated for single phase α-C3N4 and β-C3N4 respectively. The experimental X-ray spectra of films deposited on both Si and Pt substrates showed all the strong peaks of α-C3N4 and β-C3N4 so the films are mixtures of α-C3N4 and β-C3N4. The N/C atomic ratio is in the range of 1.0–2.0. X-ray photoelectron spectroscopy (XPS) analysis indicated that the binding energy of Is and N ls are 286.2 eV and 399.5 eV respectively, corresponding to polarized C-N bond. Fourier transform infrared absorption (FT-IR) and Raman spectra support the existence of C-N covalent bond in the films. Nano-indentation hardness tests showed that the bulk modulus of a film deposited on Pt is up to 349 GPa [ABSTRACT FROM AUTHOR]

Zn1-xMnxO nanowires were synthesized through chemical vapor deposition of pure Zn and MnCI2 power mixtures on silicon substrates. The morphology, structure and composition were measured by SEM, TEM, EDX and XRD. Magnetic proper- ties were measured by SQUID. The results show that the nanowires exhibit clear ferromagnetic behavior at low temperature. An abnormal peak is observed in the M-T curve at 55 K in a magnetic field of 500 Oe. [ABSTRACT FROM AUTHOR]

Water-related energy is an inexhaustible and renewable energy resource in our environment, which has huge amount of energy and is not largely dictated by daytime and sunlight. The transparent characteristic plays a key role in practical applications for some devices designed for harvesting water-related energy. In this paper, a highly transparent triboelectric nanogenerator (T-TENG) was designed to harvest the electrostatic energy from flowing water. The instantaneous output power density of the T-TENG is 11.56 mW/m2. Moreover, with the PTFE film acting as an antireflection coating, the maximum transmittance of the fabricated T-TENG is 87.4%, which is larger than that of individual glass substrate. The T-TENG can be integrated with silicon-based solar cell, building glass and car glass, which demonstrates its potential applications for harvesting waste water energy in our living environment and on smart home system and smart car system. [ABSTRACT FROM AUTHOR]