Liao Qingliang

Design and tailoring of patterned ZnO nanostructures for energy conversion applications

ZnO is a typical direct wide-bandgap semiconductor material, which has various morphologies and unique physical and chemical properties, and is widely used in the fields of energy, information technology, biomedicine, and others. The precise design and controllable fabrication of nanostructures have gradually become important avenues to further enhancing the performance of ZnO-based functional nanodevices. This paper introduces the continuous development of patterning technologies, provides a comprehensive review of the optical lithography and laser interference lithography techniques for the controllable fabrication of ZnO nanostructures, and elaborates on the potential applications of such patterned ZnO nanostructures in solar energy, water splitting, light emission devices, and nanogenerators. Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure, enlarged surface area, and improved light capture ability, which realize the efficient carrier regulation, achieve highly efficient energy conversion, and meet the diverse requirements of functional nanodevices. The patterning techniques proposed for the precise design of ZnO nanostructures not only have important guiding significance for the controllable fabrication of complex nanostructures of other materials, but also open up a new route for the further development of functional nanostructures.摘要ZnO作为典型的直接带隙宽禁带半导体材料具有丰富的形貌结构和独特的物理、 化学性能, 被广泛应用于能源、 信息技术、 生物医学等领域. 目前纳米结构的精确设计与可控制备已成为改善ZnO基功能型纳器件性能的重要手段. 本论文介绍了利用图案化技术对ZnO纳米结构进行限域生长的技术手段, 重点综述了光刻技术和激光干涉模板法在精细ZnO纳米结构制备方面的研究进展, 及其在光伏电池、 光电化学电池、 发光器件和纳米发电机四种能量转换器件中的应用. 形貌结构可调的ZnO纳米结构具有分立的高精度空间纳米结构、 增大的比表面积、 提升的光子捕获能力, 在与其他材料复合时利于实现高效的载流子行为调控, 获得了高效的能量转换, 满足了不同 功能型纳器件对材料结构的需求. 针对ZnO纳米结构精确设计所发展的一系列图案化技术对其他材料的复杂纳米结构可控制备具有重要的指导意义, 亦为功能型纳器件的进一步发展开辟了一个全新的途径.

Quasi One-dimensional ZnO Nanostructures Fabricated without Catalyst at Lower Temperature

One- or quasi one-dimensional zinc oxide nanostructures possess plenty of morphologies. Only by controlling the gas flow rates, and partial pressures of argon, oxygen and zinc vapor, can various types of high-quality ZnO nanomaterials (such as wires, belts, arrays, saws or combs, tetraleg rods, nails, and pins) be synthesized through pure zinc powder evaporation without a catalyst at the temperature range of 600–700°C. In this study, deposited nanostructures were characterized by means of scanning electron microscopy, X-ray diffraction and high-resolution transmission electron microscopy. The authors propose and discuss the growth mechanisms of various ZnO. In addition, properties of room temperature photoluminescence and field emission of several typical ZnO nanostructures are measured and investigated.

Study on the Effect of Secondary Banded Structure on the Fatigue Property of Non-Quenched and Tempered Micro Alloyed Steel

Due to composition segregation and cooling speed, streamline or banded structure were often obtained in the thermal forming parts along the direction of parts forming. Generally speaking, banded structure doesn’t decrease the longitudinal mechanical properties, so the secondary banded structure can’t get enough attention. The effect of secondary banded structure on the fatigue properties of micro alloyed DG20Mn and 35CrMo steel was investigated using the axial tensile fatigue test of stress ratio of 0.1. The result shows that secondary banded structure was obtained in the center of the steel parts, because of the composition segregation and the lower cooling rate in center part of steel. Secondary banded structure has no significant effect on axial tensile properties of both DG20Mn and 35CrMo, but decreases the axial tensile fatigue performance of DG20Mn steel. This study suggests that under the high cyclic tensile stress, multi-source damage cracks in steel initiated by large strain of pearlite of secondary banded structure, which is larger than damage strain, is the major factor of the decrease of fatigue life of steel.

Schottky junction based self-powered photodetectorsand their performance modulation by multifield coupling effect

Aiming to overcome the limitation of manufacturing technology at atomic scale, “More than Moore’s law” has been recognized as a promising route to develop the next generation micro-nano electronics in the recent years. These new devices have been designed to minimize the non-digital units to nanoscale and to integrate these units into a multifunctional electronic system. The non-digital units usually contain the power source, sensing units, charge transfer devices, switches, amplifier and etc.

Morphological effects on the field emission characteristics of zinc oxide nanotetrapods films

The direct growth of a tetrapod-like ZnO nanostructure has been accomplished by using a thermal oxidation method without any catalysts. Studies on the field emission properties of the ordered ZnO nanotetrapods films found that the shape of the ZnO nanotetrapods has considerable effect on their field emission properties, especially the turn-on field and the emission current density. Compared with the rod-like legs ZnO nanotetrapods, the nanotetrapods with acicular legs have a lower turn-on field of 2.7 V/μm at a current density of 10 μA/cm2, a high field enhancement factor of 1830, and an available stability. More importantly, the emission current density reached 1 mA/cm2 at a field of 4.8 V/μm without showing saturation. The results could be valuable for using the ZnO nanostructure as a cold-cathode field-emission material.