Engineered resonant tunnelling nanostructures for the Terahertz realm

The engineering of the metal/insulator nanostructures capable of harnessing THz energy is the central aim of this project. The challenge lies in tuning the barrier heights at the metal/insulator interfaces for optimal terahertz energy conversion. Instrumental in achieving this ambitious goal is thorough understanding of interfacial barrier formation and correlation of physical and electrical properties of proposed nanostructures. The nanostructures will be fabricated using atomic layer deposition (ALD). The ALD deposition system enables a controlled microstructure, leading to better uniformity and control of the tunnelling barriers' composition and thickness, as well as interface integrity and stability. The target is addressed in three coupled work phases, which are strongly linked, and entail voluminous theoretical and experimental study with a wide range of characterization techniques.

The successful outcome of the project will facilitate an emerging technology and complement research efforts at Manchester University and Imperial College in the UK to bring about new efficient electronic devices for terahertz energy harvesting in infrared and visible domain.

The aim of the proposed project is to provide terahertz metal/insulator-based nanodiodes of small geometry, ability to function without biasing, high speed, room temperature operation and frequency selectivity. Additional advantage is the CMOS compatibility of the metal/insulator technology, which means easy integration, scale-up and low cost for these devices. The successful completion of the project will point to feasibility of proposed nanostructures to perform beyond the current state-of-the-art approaches to contribute to compact, fast and affordable terahertz system architectures. The project outcome is expected to make a significant impact on a wide range of disciplines and the general public.

Terahertz radiation will, due to its long wavelength, penetrate many materials such as clothing, packing materials, and certain construction materials. Therefore, there is significant interest in the development of imaging methods that can combine this 'see-through' capability with the spectroscopic information that materials such as explosives, pharmaceutical, and narcotic materials contains in the terahertz range. Practical applications of terahertz systems are many: security applications (body scanners, concealed powders in postal mail), medical imaging (without hazard of X-rays), pharmaceutical industry (quality control of tablet coatings), food industry (detection of foreign bodies in eatables, quality control), plastics industry (in-line monitoring of polymeric compounding processes, the quality control of plastic weld joints, etc.), paper industry (to monitor the thickness and moisture content of the paper during the production process), art conservation (information on the thickness of the hidden paint layers) and others.

The ultimate aim is to integrate these high-frequency diodes directly into the nantennas. An array of the nantennas can be printed using conductive metals (like gold) onto a flexible sheet of polymer or a thin metal foil. It is inexpensive, non-toxic, light weight, and operates at room temperature and it has a wide angle of acceptance, so no need to change its angle with respect to the emitter to maintain its efficiency. The energy from infrared spectrum can be received to harvest industrial waste heat. A 1% increase in efficiency by converting some waste heat into electricity would save billions of pounds per year. As such, nantennas will be complementary to photovoltaics (PV), offering increased efficiencies through thermal harvesting when coupled to existing solar PV collection devices.

A further major outcome of the project is its excellent potential to generate wealth in the UK by the worldwide sale of precursors developed for atomic layer deposition. SAFC Hitech is a major supplier of precursors and support the project.