Skowron Stephen T, Roberts Sarah L, Khlobystov Andrei N, Besley Elena
School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
Micron. 2019 May;120:96-103. doi: 10.1016/j.micron.2019.02.007. Epub 2019 Feb 21.
Encapsulation of materials imaged by high resolution transmission electron microscopy presents a promising route to the reduction of sample degradation, both independently and in combination with other traditional solutions to controlling radiation damage. In bulk crystals, the main effect of encapsulation (or coating) is the elimination of diffusion routes of beam-induced radical species, enhancing recombination rates and acting to limit overall damage. Moving from bulk to low dimensional materials has significant effects on the nature of damage under the electron beam. We consider the major changes in mechanisms of damage of low dimensional materials by separating the effects of dimensional reduction from the effects of encapsulation. An effect of confinement is discussed using a model example of coronene molecules encapsulated inside single walled carbon nanotubes as determined from molecular dynamics simulations calculating the threshold energy required for hydrogen atom dissociation. The same model system is used to estimate the rate at which the nanotube can dissipate excess thermal energy above room temperature by acting as a thermal sink.
通过高分辨率透射电子显微镜成像的材料封装，无论是单独使用还是与其他控制辐射损伤的传统解决方案相结合，都为减少样品降解提供了一条有前景的途径。在块状晶体中，封装（或涂层）的主要作用是消除束流诱导自由基物种的扩散途径，提高复合率并限制整体损伤。从块状材料转向低维材料会对电子束下的损伤性质产生重大影响。我们通过将尺寸减小的影响与封装的影响分开，来考虑低维材料损伤机制的主要变化。利用分子动力学模拟计算氢原子解离所需的阈值能量，以 coronene 分子封装在单壁碳纳米管内的模型示例讨论了限制效应。相同的模型系统用于估计纳米管作为热沉在室温以上耗散多余热能的速率。
