Cryogenic Ultrafast Scattering-type Terahertz-probe Optical-pump Microscopy (CUSTOM)

Lead Research Organisation: University of Manchester
Department Name: Electrical and Electronic Engineering

Abstract

Technology underpins our society and economy and devices are constantly evolving, becoming smaller, faster, and 'smarter'. However, current technologies are fast approaching their physical limit and suffer from high, inefficient power consumption and poor energy storage. Integrated photonic, electronic and quantum technologies have the potential to disrupt these existing technologies, providing '21st-century products' with improved performance including energy efficiency. These devices will have a broad range of applications and will impact several sectors, such as healthcare, defence and security, ICT, and clean energy. Advanced functional materials, including graphene, 2D materials and semiconductor nanostructures, are the building blocks of these devices with the potential to deliver a step-change in performance through exploitation of novel quantum effects. An in-depth understanding of their electronic, photonic and spintronic properties, and how they may be controlled, enhanced and exploited is therefore essential.

Although several characterisation techniques exist it still remains difficult to obtain a complete picture of their optoelectronic/spintronic behaviour. Often a combination of methodologies are required to extract device parameters, such as charge carrier mobility and lifetime; and these techniques have their own limitations - they can be destructive, only perform ensemble measurements, or only operate at room temperature and ambient pressure. Notably, material characterisation remains challenging on nanometre length scales, with the majority of techniques limited in resolution to the micron scale. As the majority of devices rely on controlling and designing electronic behaviour at the nanoscale (e.g. pn junctions), nanoscale spatial resolution is essential for accelerating device development. There is therefore an urgent need for state-of-the-art research infrastructure that can provide nanometre spatial resolution and combine the strengths of current methodologies to investigate materials over a large parameter range.

The proposed investment will establish a new national facility for advanced nanoscale material characterisation and will provide the 'missing tool' required to conduct simultaneous imaging and spectroscopy at 3 extremes: ultrafast (<1ps) timescales, nanoscale (<30nm) length scales, and low temperatures (<10K). By combining ultrafast THz and midinfrared (MIR) spectroscopy with cryogenic scattering-type near-field optical microscopy, this facility will provide an exclusive tomographic tool that allows surface-sensitive, non-destructive optoelectronic characterisation of individual nanomaterials over a temperature range of 4.2-300K. As the THz and MIR frequency range encompasses the energy range of several fundamental quasiparticles (e.g. plasmons, free electrons and holes, and magnons), this capability will open up a new parameter range for investigating low-energy excitations in advanced functional materials, including III-V nanowires, 2D materials, topological insulators, and chalcogenides. It will allow differential depth-profiling and 3D mapping of the local dielectric function, electrical conductivity, chemical composition, stress/strain fields with <30nm spatial resolution, and enable investigation of nanoscale photoinduced carrier dynamics and ultrafast vibrational dynamics with <1ps temporal resolution. The facility will be unique to the UK/EU and will provide unprecedented capability for advanced functional materials research. Access to the tool will be made available to UK academics and industry undertaking research in this area. The system will be housed within the UK National Laboratory for Advanced Materials (the Henry Royce Institute) at the University of Manchester and will link with other key materials research infrastructure, such as P-NAME and Royce MBE systems, to form a key chain in the feedback loop between materials optimisation and device development.

Planned Impact

World-leading capability:
CUSTOM will ensure that the UK remains an international leader in advanced materials research, by providing state-of-the-art research infrastructure for near-field THz/MIR imaging and spectroscopy that will increase nanoscale material characterisation capability. It will further cement the University of Manchester as one of the world's most innovative universities and a centre of excellence for 'advanced materials', one of its six research beacons. Established within the Henry Royce Institute (Royce), it will support several EPSRC strategic research areas (e.g. materials for energy-efficient ICT, clean energy) and wider Royce investments in advanced materials deposition and development (e.g. MBE, PECVD, P-NAME) across the UK. It will be available as a national resource to UK academics and industry, enhancing several research programmes.

Economy
By providing a detailed understanding of new advanced materials, this facility will accelerate the development of future technologies. These next-generation devices will provide a step-change in performance and energy efficiency and, in turn, contribute to the UK's knowledge-based economy and improve productivity. The development and application of advanced materials has been identified as a key requirement for growth by the International Roadmap of Devices and Systems (IRDS) [19]. Current production and processing of materials accounts for 15% of UK GDP consisting of ~£170bn turnover and ~£50bn of export; new advanced materials are expected to further impact the national economy [18]. On a more regional scale, the facility is in direct alignment with the Greater Manchester Local Industrial Strategy, as well as the Northern Powerhouse, which is a government priority. The strategic placement of this facility within Royce at Manchester ensures that CUSTOM will benefit industry and stakeholders. It will also exploit the industrial connections offered by Royce at higher levels (e.g. CEO, CTOs), to accerate the route between material and device development and translation to market.

Knowledge
This facility will provide unprecedented capability to examine promising new materials simultaneously at nanometre length scales and low temperatures with surface-sensitivity. This will open up a new parameter range for advanced material study, which will not only enhance current understanding of material properties, but will also allow theoretically-predicted behaviour to be experimentally observed for the first time. The ability to probe materials in a non-destructive fashion at the nanoscale is also crucial for device development. As device functionality relies on control of optoelectronic properties at the nanoscale (e.g. p-n junctions), there is a need to also examine these properties on the same length scale. This facility will therefore address this need allowing <30nm spatial resolution characterisation, forming a key link in the feedback loop between material optimisation and device development.

Society
By providing a new understanding of advanced functional materials, this facility will assist in the development of future technologies, which will impact on society. For example, provision of materials that replace electronic with photonic technologies would profoundly affect how we communicate. Whereas, integrating current quantum technologies being developed and non-quantum devices would remove a barrier to their future wide-scale adoption. These advanced functional materials will have a several applications in a range of sectors, including UK defence and security and healthcare. The research enabled by CUSTOM is therefore expected to influence government policy by offering replacement technologies.

People
This facility will be made widely available to UK academic and industry, with 'free' access for postgraduate students provided through Royce, allowing them to enhance the impact of their research and further development of their careers.

Publications

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