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

狄拉克材料由于其良好的表面态和掺杂可调性，已成为节能器件应用的有前途的候选材料。最近的研究也表明，它们是太赫兹辐射的良好发射者。通过利用它们的能带结构拓扑，还可以实现对发射的THz波形的全光控制。特别是，通过切换光激发光的螺旋度可以简单地实现偏振控制。这是太赫兹器件应用的一个重要结果，因为到目前为止，偏振控制一直难以捉摸，需要脉冲整形。该项目将研究新型低维拓扑材料，如狄拉克半金属砷化镉，以评估其在太赫兹器件应用中的适用性。太赫兹光谱学和显微技术将分别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。这将允许在两个长度尺度上绘制关键的传输参数，如迁移率、载流子寿命和非本征载流子浓度，为控制这些材料中的传输的基本物理机制提供独特的见解，这些传输将直接提供给下一代设备(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).