Terahertz, Topology, Technology: Realising the potential of nanoscale Dirac materials using near-field terahertz spectroscopy

太赫兹、拓扑、技术：利用近场太赫兹光谱实现纳米级狄拉克材料的潜力

• 批准号: MR/T022140/1
• 负责人: Jessica Boland
• 金额: $ 155.65万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FT022140%2F1
• 关键词: Terahertz; Topology; Technology; Realising; potential

Technology is constantly evolving. Even within our lifetime, devices have become noticeably faster and smaller with increased functionality; yet these 'smart' devices still suffer from high power consumption and poor energy storage. Integrative photonic, electronic and quantum technologies are key to creating the next-generation of devices that are more energy-efficient with unprecedented performance. These '21st century products' will have a huge impact on a range of sectors, including healthcare, wireless communication, defence, security and clean energy. Advanced functional materials, including graphene, 2D materials and III-V nanowires, will form the basis of these new technologies. Dirac materials, in particular, have attracted significant attention as candidates for novel devices, owing to their extraordinary optoelectronic properties. Dirac semi-metals (DSM) form a 3D analogue of graphene. Whereas topological insulators (TI) are insulating in the bulk, yet possess perfectly conducting surface states. For both materials, the surface hosts Dirac electrons that travel close to the speed of light and are immune to backscattering from non-magnetic impurities and defects. Their direction of travel is fixed by their inherent angular momentum or 'spin', so they behave as if on a railway line - travelling with less resistance and heat production. This coupling between an electron's charge and spin renders TIs and DSMs useful for quantum computing and spintronic applications. In particular, these materials have emerged as promising candidates for novel terahertz (THz) devices. THz technologies are poised to impact several sectors, including security, food processing, healthcare and wireless communication. To realise their full potential, an in-depth understanding of key device parameters (e.g. conductivity) in active THz materials is vital. THz time-domain spectroscopy (THz-TDS) has arisen as a powerful ultrasensitive, non-contact probe of electrical conductivity. It has already been used to examine TIs and DSMs and has shown they possess a high effective electron mobility as a result of reduced impurity scattering. However, so far these measurements have been limited in spatial resolution by the diffraction limit of light (150um for 1THz). The measured conductivity averages over any inhomogeneity and is dominated by the bulk response. Local information is therefore lost and it has proven difficult to isolate the surface conductivity from that of the bulk. This research project aims to push THz-TDS down to the nanoscale, extending the spatial resolution to nanometre length scales. It will employ scattering-type near-field optical microscopy (SNOM) with ultrafast optical-pump terahertz-probe (OPTP) spectroscopy (OPTP-SNOM) to provide a non-destructive, surface-sensitive, nanoscale probe of electrical conductivity. This unique tool will be applied to individual TI and DSM nanostructures to isolate and map their surface photoconductivity response for the first time with <30nm spatial and <1ps temporal resolution. Nano-tomography will form a 3D map of local carrier concentration, carrier lifetime and electron mobility, providing deeper insight into surface carrier transport. Utilising this newfound knowledge, the exclusive P-NAME facility will be used to spatially dope optimised TI and DSM nanostructures for use in THz emitters and detectors. This tool enables a single ion to be positioned with <40nm spatial accuracy, providing control of electronic properties on nanometre length scales. OPTP-SNOM will be used to image dopants and examine nanoscale conductivity, providing a direct feedback loop between material and device optimisation. This capability will allow the advantageous properties of Dirac materials to be fully exploited, leading to a step-change in performance. These THz devices are expected to surpass performance of current state-of-the-art THz devices, opening a pathway for THz technologies to impact on today's society.

技术在不断发展。即使在我们的有生之年，随着功能的增加，设备已经变得明显更快，更小;然而这些“智能”设备仍然存在高功耗和低能量存储的问题。集成的光子、电子和量子技术是创造下一代设备的关键，这些设备具有前所未有的性能和更高的能效。这些"世纪产品“将对医疗保健、无线通信、国防、安全和清洁能源等一系列领域产生巨大影响。先进的功能材料，包括石墨烯，2D材料和III-V纳米线，将成为这些新技术的基础。特别是狄拉克材料，由于其非凡的光电性能，作为新型器件的候选者引起了极大的关注。狄拉克半金属（DSM）形成石墨烯的3D类似物。而拓扑绝缘体（TI）是绝缘的，但具有完美的导电表面状态。对于这两种材料，表面承载着以接近光速行进的狄拉克电子，并且不受非磁性杂质和缺陷的反向散射的影响。它们的运动方向是由其固有的角动量或“自旋”固定的，因此它们的行为就像在铁路线上一样-以较小的阻力和产热行驶。电子的电荷和自旋之间的这种耦合使得TI和DSM可用于量子计算和自旋电子学应用。特别是，这些材料已经成为新型太赫兹（THz）器件的有前途的候选人。太赫兹技术将影响多个领域，包括安全、食品加工、医疗保健和无线通信。为了充分发挥其潜力，深入了解有源THz材料中的关键器件参数（例如电导率）至关重要。太赫兹时域光谱（THz-TDS）是一种超灵敏、非接触式的电导率测量技术。它已经被用来检查TI和DSM，并已表明，他们拥有一个高的有效电子迁移率作为减少杂质散射的结果。然而，到目前为止，这些测量在空间分辨率上受到光的衍射极限（1 THz为150 μ m）的限制。测量的电导率在任何不均匀性上平均，并且由体响应主导。因此，局部信息丢失，并且已经证明难以将表面电导率与体电导率隔离。该研究项目旨在将THz-TDS推向纳米级，将空间分辨率扩展到纳米长度尺度。它将采用散射型近场光学显微镜（SNOM）与超快光泵太赫兹探测（OPTP）光谱（OPTP-SNOM），以提供一种非破坏性的，表面敏感的，纳米级的电导率探针。这种独特的工具将应用于单个TI和DSM纳米结构，以首次以<30 nm的空间分辨率和<1 ps的时间分辨率分离和映射其表面光电导响应。纳米断层扫描将形成局部载流子浓度、载流子寿命和电子迁移率的3D地图，从而更深入地了解表面载流子传输。利用这一新发现的知识，独家P-NAME设施将用于空间掺杂优化的TI和DSM纳米结构，用于THz发射器和探测器。该工具能够以<40 nm的空间精度定位单个离子，从而在纳米长度尺度上控制电子特性。OPTP-SNOM将用于成像掺杂剂和检查纳米级导电性，在材料和器件优化之间提供直接反馈回路。这种能力将使狄拉克材料的有利特性得到充分利用，从而导致性能的阶跃变化。这些THz器件的性能有望超过目前最先进的THz器件，为THz技术影响当今社会开辟了一条道路。

项目成果

Topological Dirac semi-metals as novel, optically-switchable, helicity-dependent terahertz sources

拓扑狄拉克半金属作为新型、光学可切换、螺旋度相关的太赫兹源

• DOI: 10.1109/irmmw-thz50927.2022.9895566
• 发表时间: 2022
• 作者: Boland J

Unveiling the ultrafast optoelectronic properties of 3D Dirac semi-metal Cd 3 As 2

揭示 3D 狄拉克半金属 Cd 3 As 2 的超快光电特性

• DOI: 10.1109/irmmw-thz46771.2020.9370806
• 发表时间: 2020
• 作者: Boland J

Investigating the Effect of Crystal Morphology on Optoelectronic Properties of Zinc Phosphide Thin Films via Optical-pump Terahertz Probe Spectroscopy

通过光泵太赫兹探针光谱研究晶体形态对磷化锌薄膜光电性能的影响

• DOI: 10.1109/irmmw-thz57677.2023.10299122
• 发表时间: 2023
• 作者: Huang Y

Topological materials as promising candidates for tuneable helicity-dependent terahertz emitters

• DOI: 10.1117/12.2681745
• 发表时间: 2023-10
• 期刊: Review of Palaeobotany and Palynology
• 影响因子: 1.9
• 作者: J. Boland;D. Damry;Chelsea Q. Xia;Y. Saboon;A. Mannan;Piet Schoenherr;D. Prabhakaran;Laura M. Herz;T. Hesjedal;Michael B. Johnston

THz characterization of GeSn monocrystalline thin films

GeSn 单晶薄膜的太赫兹表征

• DOI: 10.1109/irmmw-thz50927.2022.9895959
• 发表时间: 2022
• 作者: Liu X