Shen Yan, Han Yuchen, Zhan Runze, Chen Xuexian, Wen Shiya, Huang Wuchao, Sun Fengsheng, Wei Yaoming, Chen Huanjun, Wu Jin, Chen Jun, Xu Ningsheng, Deng Shaozhi
State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, People's Republic of China.
ACS Appl Mater Interfaces. 2020 May 27;12(21):24218-24230. doi: 10.1021/acsami.0c02351. Epub 2020 May 6.
Specific geometric morphology and improved crystalline properties are of great significance for the development of materials in micro-nano scale. However, for high-melting molybdenum (Mo), it is difficult to get high-quality structures exhibiting a single-crystalline nature and preconceived morphology simultaneously. In this paper, a pyramid-shaped single-crystalline Mo nanostructure was prepared through a thermal evaporation technique, as well as a series of experimental controls. Based on detailed characterizations, the growth mechanism was demonstrated to follow a sequential process that includes MoO decomposition and Mo deposition, single-crystalline islands formation, layered nucleation, and competitive growth. Furthermore, the product was measured to show excellent physical properties. The prepared nanostructures exhibited strong nano-indentation hardness, elastic modulus, and tensile strength in mechanical measurements, which are much higher than those of the Mo bulks. In the measurement of electronic characteristics, the individual structures indicated very good electrical transport properties, with a conductance of ∼0.16 S. The prepared film with an area of 0.02 cm showed large-current electron emission properties with a maximum current of 33.6 mA and a current density of 1.68 A cm. Optical properties of the structures were measured to show obvious electromagnetic field localization and enhancement, which enabled it to have good surface enhanced Raman scattering (SERS) activity as a substrate material. The corresponding structure-response relationships were further discussed. The reported physical properties profit from the basic features of the Mo nanostructures, including the micro-nano scale, the single-crystalline nature in each grain, as well as the pyramid-shaped top morphology. The findings may provide a potential material for the research and application of micro-nano electrons and photons.
特定的几何形态和改善的晶体性质对于微纳尺度材料的发展具有重要意义。然而，对于高熔点的钼（Mo）而言，很难同时获得具有单晶性质和预设形态的高质量结构。本文通过热蒸发技术以及一系列实验控制制备了金字塔形单晶Mo纳米结构。基于详细的表征，证明其生长机制遵循一个连续的过程，包括MoO分解和Mo沉积、单晶岛形成、层状成核以及竞争生长。此外，测量结果表明该产物具有优异的物理性能。在力学测量中，制备的纳米结构表现出很强的纳米压痕硬度、弹性模量和拉伸强度，远高于块状Mo。在电子特性测量中，单个结构显示出非常好的电输运性能，电导约为0.16 S。制备的面积为0.02 cm²的薄膜表现出大电流电子发射特性，最大电流为33.6 mA，电流密度为1.68 A/cm²。测量了该结构的光学性质，结果表明其具有明显的电磁场局域化和增强，使其作为基底材料具有良好的表面增强拉曼散射（SERS）活性。进一步讨论了相应的结构-响应关系。所报道的物理性能得益于Mo纳米结构的基本特征，包括微纳尺度、每个晶粒中的单晶性质以及金字塔形顶部形态。这些发现可能为微纳电子和光子的研究与应用提供一种潜在材料。
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