Nanoscale optoelectronic characterisation of low-dimensional Dirac materials for terahertz device applications

由于其完美的导电表面状态和掺杂可调性，狄拉克材料已成为节能器件应用的有希望的候选者。最近的研究也表明，它们是太赫兹辐射的良好发射器。利用其带结构拓扑，也可以实现发射太赫兹波形的全光控制。特别是，偏振控制可以简单地通过切换光激发光的螺旋度来实现。这对于太赫兹器件的应用来说是一个重要的结果，因为迄今为止偏振控制一直是难以捉摸的，并且需要脉冲整形。该项目将研究新的低维拓扑材料，如狄拉克半金属砷化镉，以评估太赫兹器件应用的适用性。太赫兹光谱学和显微镜将分别用于在微米和纳米尺度上对这些材料进行非接触、非破坏性的光电表征。这将允许关键的传输参数，如迁移率，载流子寿命和外在载流子浓度，在两个长度尺度上进行映射，为这些材料中控制传输的潜在物理机制提供独特的见解，这将直接用于下一代设备（即太赫兹光电探测器）的开发。

Dirac materials have emerged as promising candidates for energy-efficient device applications, owing to their perfectly-conducting surface states and doping tuneability. Recent studies have also demonstrated that are good emitters of terahertz radiation. By exploiting their bandstructure topology, all-optical control of the emitted THz waveform can also be accomplished. In particular, polarisation control can be achieved simply by switching the helicity of photoexcitation light. This is an important result for terahertz device applications, as to date polarisation control has been elusive and required pulse shaping. This project will investigate novel low-dimensional topological materials, such as the Dirac semi-metal cadmium arsenide, to assess the suitability for terahertz device applications. Terahertz spectroscopy and microscopy will be used to perform non-contact, non-destructive optoelectronic characterisation of these materials on micron and nanometre length scales respectively. This will allow key transport parameters, such as mobility, carrier lifetime and extrinsic carrier concentration, to be mapped on both length scales, providing unique insight into the underlying physical mechanisms governing transport in these materials that will directly feed into development of next-generation devices (namely terahertz photodetectors).