Modelling and characterisation of electron beam processed low dimensional nanomaterials

科学背景与合作高分辨率透射电子显微镜（HRTEM）已成为研究低维纳米材料结构的常用工具，如石墨烯或碳纳米管。除了在原子尺度上进行结构分析之外，提高TEM当前能力的主要挑战包括：1 .将TEM建立为材料动态转变定量表征的主要工具；二是利用电子束作为直接加工工具，实现对低维材料进行可控改性的新型合成路线。HRTEM和STEM的一个范例转变是对纳米材料中单个原子的控制和定位，称为“原子锻造”。HRTEM的最新进展为原子精度控制材料铺平了道路，这一过程目前只能通过扫描隧道显微镜（STM）实现，但具有室温稳定性和整个材料3D体积可访问性的固有优势。将电子束作为终极合成工具的梦想变为现实，需要从理论上和实验上全面理解材料的基本特性，即它们在电子束加工下的动态行为和相互作用。该博士项目将重点研究电子束辐照下的材料，结合计算建模和成像与原子尺度分辨率的见解，预测和解释在TEM中处理的低维纳米材料的动态行为。它将涉及理论预测的密切，迭代的比较，贝斯利，化学与实验透射电镜观察，布朗，工程。该项目将利用化学学院计算纳米科学小组的广泛专业知识，涵盖广泛的计算技术，从模拟接近500k原子的经典势的大规模系统到高密度泛函理论计算。电子束对结构转换的动态影响将使用小组内部的CompuTEM算法进行明确的建模，从而产生多层图像模拟，以便与原子分辨率的实验TEM图像进行直接比较。

Scientific context and collaborationHigh resolution transmission electron microscopy HRTEM has become a common tool for studying the structures of low dimensional nanomaterials, such as graphene or carbon nanotubes. Major challenges in advancing the current capabilities of TEM, beyond structural analysis on the atomic-scale, include 1 establishing TEM as the primary tool for the quantitative characterisation of material dynamic transformations; and 2 enabling novel synthetic routes for the controlled modification of low-dimensional materials using the electron beam e-beam as a direct processing tool. A paradigm shift for HRTEM and STEM is the controlled manipulation and positioning of individual atoms within a nanomaterial, termed "The Atomic Forge". The latest advances in HRTEM are paving the way for the control of materials with atomic precision, a process currently achievable only by scanning tunnelling microscopy STM, but with the inherent advantages of stability at room temperature and accessibility throughout the 3D volume of the material, free of the low temperature surface assembly limitations associated with STM Turning the dream of using the e- beam as the ultimate synthetic tool into a reality requires comprehensive understanding, both theoretically and experimentally, of material properties at the fundamental level, in terms of their dynamic behaviour and interaction under the processing e-beam. This PhD project will focus on the investigation of materials under e-beam irradiation, combining the insights of computational modelling and imaging with atomic scale resolution, to predict and explain the dynamic behaviour of low dimensional nanomaterials processed in the TEM. It will involve the close, iterative comparison of theoretical predictions Besley, Chemistry with experimental TEM observations Brown, Engineering. The project will take advantage of the extensive expertise, based in the Computational Nanoscience group, in the School of Chemistry, across a wide range of computational techniques, from modelling large scale systems approaching 500k atoms with classical potentials to high-level density functional theory calculations. The dynamic effects of the e-beam on structure transformations will be modelled explicitly using the group's in-house CompuTEM algorithm resulting in multislice image simulations for direct comparison with experimental TEM images with atomic resolution.