A yellow-orange nitrogen-doped zinc oxide (ZnO:N) film was deposited on a quartz glass substrate at 510K by reactive radio-frequency magnetron sputtering of a ZnO target with sputtering gas of nitrogen. The lattice constants of the as-grown ZnO:N are much larger than those of undoped ZnO, and decrease with increasing annealing temperature due to escape of the nitrogen from the ZnO:N and decrease of tensile stress, accompanied with color change from yellow-orange to pale yellow. The nitrogen occupies two chemical environments in the ZnO:N based on x-ray photoelectron spectroscopy measurement. One is NO acceptor formed by substitution of N atom for O sublattice, and another is (N2)O double donors produced by substitution of N molecular for O site, which make the lattice constants expanded. The as-grown ZnO:N film shows insulating, but behaves p-type conduction in the dark after annealed at 863K for 1h under 10−3Pa. Unfortunately, the p-type conduction is not stable and reverts to n type soon. However, after illuminated by sunlight for several minutes, the n-type ZnO:N transforms into p type again. The mechanism of the transformation of the conductivity behavior is discussed in the present work.
To improve ZnO thin film quality, the ZnO thin films grown on silicon (100) by plasma enhanced chemical vapour deposition from Zn(C2H5)2 and CO2 gas mixtures at a low temperature of 120°C are annealed in an oxygen ambient at temperature ranging from 600°C to 1000°C. X-ray diffraction spectra indicate that ZnO films possess a polycrystalline hexagonal wurtzite structure. Atomic force microscopy results show an increase of ZnO grain size with the increase of annealing temperature. The photoluminescence is closely related to the annealing temperature. The free exciton binding energy deduced from the temperature-dependent PL spectra is about 59 meV for the ZnO film annealed at 900°C, suggesting that the film quality can be improved by annealing process.
ZnO particles embedded in SiO2 thin films were prepared by a radio-frequency magnetron sputtering technique. X-ray diffraction (XRD) and optical-absorption spectra showed that ZnO particles with hexagonal wurtzite structure had been embedded in the SiO2 matrix, and the size of ZnO particles increased with increasing annealing temperature from 773to973K. Raman-scattering and Fourier transform infrared (FTIR) spectrum measurements also confirmed the presence of ZnO particles. When the annealing temperature was lower than 973K, room-temperature photoluminescence (PL) spectra showed dominative deep-level emissions in the visible region and very weak ultraviolet emissions. As the annealing temperature increased to 973K, an emission band in the ultraviolet region besides the emissions from free and bound excitons recombination was observed in the low-temperature PL spectra. The origin of the ultraviolet emission bands was discussed with the help of temperature-dependent PL spectra. When the annealing temperature was higher than 973K, Zn2SiO4 particles were formed, as shown by XRD and FTIR results.
This paper reviews the current state of dynamic sealing technologies, examining the challenges faced by conventional sealing methods under complex working conditions, such as high temperature, high pressure, and corrosive environments. It also provides a concise overview of the status and developmental trends in sealing inspection technologies. From the perspective of obstruction mechanisms, this study reinterprets the concept of sealing science by redefining the classification of sealing types based on solid-phase medium obstruction, fluid hydrostatic and hydrodynamic obstruction, fluid pumping obstruction, fluid energy dissipation obstruction, and fluid impact obstruction. Comparative analyses of sealing structures across these obstruction mechanisms are presented. The sealing technology based on fluid impact medium obstruction, newly proposed by this paper, represents an innovative sealing approach. It offers distinct advantages such as zero wear, structural simplicity, and high stability, addressing longstanding issues in high-speed, large-clearance non-contact seals, including low leakage suppression efficiency, system complexity, and poor stability. Since its introduction, this novel sealing structure has garnered significant attention and recognition from both the academic and industrial sealing communities. With the potential to revolutionize the field, this groundbreaking sealing design is poised to lead the next wave of technological advancements in sealing science.
By converting the energy of nuclear radiation to excited electrons and holes, semiconductor detectors have provided a highly efficient way for detecting them, such as photons or charged particles. However, for detecting the radiated neutrons, those conventional semiconductors hardly behave well, as few of them possess enough capability for capturing these neutral particles. While the element Gd has the highest nuclear cross section, here for searching proper neutron-detecting semiconductors, we investigate theoretically the Gd chalcogenides whose electronic band structures have never been characterized clearly. Among them, we identify that γ-phase Gd2Se3 should be the best candidate for neutron detecting since it possesses not only the right bandgap of 1.76 eV for devices working under room temperature but also the desired indirect gap nature for charge carriers surviving longer. We propose further that semiconductor neutron detectors with single-neutron sensitivity can be realized with such a Gd-chalcogenide on the condition that their crystals can be grown with good quality.
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