![]() ( e) Region1 (yellow block in d): High-magnification cross-sectional TEM image of MoS 2 layers, clearly shows the layered structure of MoS 2 nanosheets. ( d) Cross-sectional TEM image of vertically standing MoS 2 grown on SiO 2/Si substrate. ( c) AFM height profile of MoS 2 nanosheets, the insert shows the corresponding AFM image. ![]() ( b) 52.5° tilt view of MoS 2 nanosheets which clearly show the vertically standing feature. ( a) Top view FE-SEM image of vertically standing MoS 2 nanosheets. Furthermore, the field emission properties and the HER performance of vertically standing MoS 2 nanosheets were reported.Ĭharacterization of as-synthesized MoS 2 nanosheets. In addition, a possible mechanism is proposed based on the experimental results. Various characterizations techniques were used to give a deep analysis of those vertically standing MoS 2 nanosheets. In this work, we propose a method to synthesize vertically standing MoS 2 nanosheets using a conventional chemical vapor deposition (CVD) method. In addition, the growth mechanism could also promote the process in designing more complex nanometric structures. We believe that a clear understanding of the growth mechanism would facilitate the development of vertically standing materials based applications. However, there are no clear evidences demonstrating that how these transitions from 2D films to 3D clusters happened. 29 demonstrated that vertically standing graphene could be nucleated from the buffer layer or from the surface of carbon onions. 24 demonstrated that a transition from 2D complete films to 3D clusters beyond a critical layer thickness may be caused by the sufficient accumulation of strain energy and the defects of the as-deposited film during vertical graphene growth process. In contrast, the growth mechanisms for vertically standing 2D materials are still vague. Normally, nanowires and nanotubes are assumed to be grown at the interface between catalytic and nanowires (nanotubes) via vapor-liquid-solid (VLS) or vapor-solid-solid (VSS) process in 1D growth 27, 28. And the growth mechanism for vertical 1D nanowires and nanotubes are widely discussed. There have already been lots of works based on the one dimensional (1D) nanowires and nanotubes. Furthermore, It has been demonstrated that vertically growth 1D nanotubes/nanowires and 2D nanosheets with atomically thin edges can significantly improve the field emission properties 22, 23, making vertically standing 2D materials promising candidates in field emission applications 24, 25, 26. 20 demonstrate that the HER activity relates closely to the edge sites of MoS 2 flakes and the basal surfaces are catalytically inert, revealing the importance of exposed edges in catalytic reactions 21. ![]() The exposed edges with dangling bonds are chemical active and may play an important role in many catalytic reactions, such as hydrodesulfurization, hydrogen evolution reaction (HER) etc 17, 18, 19, 20. Amongst these nanometric architectures, vertically standing 2D materials hold great potential in many applications due to their high aspect ratio and extensively exposed edges 16.įor example, the minimized dimension and vertically aligned morphology of 2D materials consequently enable the fabrication of mini-sized energy storage devices with high capacity and high packing density, such as hydrogen storage devices, batteries and supercapacitors. Less of attention has been paid on their alternative configuration 13, 14, 15. However, these works have been devoted to utilize 2D materials lying flat on the substrates. Lots of efforts have been made by using 2D materials in the fields of microelectronics 7, 8, optoelectronics 9, sensors 10 and energy storage 11, 12. Due to the distinctive physical properties of one-layer thin 2D materials compared with their bulk counterparts 2, 3, layered materials have attracted much attentions, such as transition metal dichalcogenides (TMDCs) 4, transition metal oxides 5, boron nitride (BN) 6, etc. Graphene has attracted extensive interests in various research fields since it was obtained through mechanical exfoliation by Novoselov et al. ![]()
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