Unveiling electron motion at surfaces and interfaces on ultrashort length and ultrafast time scales

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics

Abstract

Semiconductor devices are becoming an increasingly important part of modern life. Smaller and faster transistors are currently powering revolutions in information technology and artificial intelligence. Furthermore, large-area thin-films of semiconductors offer a realistic solution to decarbonising the world's energy production through efficient solar to electrical energy conversion. With transistor feature sizes reaching the nanometre length scale and multijunction thin film photovoltaics offering very efficient energy production, surfaces increasingly influence the function of these devices.
Currently there are few methods available to observe the electrical properties of semiconductor surfaces and interfaces on nanometre length scales, with high enough time resolution. This Fellowship will lead the creation of a unique instrument for understanding the electrical properties of semiconductor surfaces and interfaces. The techniques of scanning tunnelling microscopy, scanning near-field optical microscopy and optical pump terahertz probe spectroscopy will be combined in a single instrument able to probe electrical properties of materials at unprecedented spatial and temporal resolution.
During the fellowship the novel instrument will be exploited to improve the power conversion efficiency and stability of solar cells by revealing the mechanisms of charge recombination, trapping and degradation at surfaces and grain boundaries. While the fellowship is focussed on study of semiconductors for energy conversion, active engagement with the wider scientific community, government and industry over the 5 years will lead to dissemination of the technique and instrumentation into other areas of surface science and beyond.

Planned Impact

This project will lead the development of a new instrument, HECS, for studying electronic properties of materials at nanometre spatial resolution and with femtosecond time resolution. This will be enabling technology for developing new electronic materials and devices. The fellowship will exploit HECS in a fundamental study of electronic properties of the surfaces and interfaces of metal halide perovskite (MHP) semiconductors and Group III-V semiconductor nanowires. These novel semiconductors are already showing great promise for efficient solar cells, however their electronic properties at surfaces, semiconductor-semiconductor interfaces, and grain boundaries are poorly understood. The advances made in this project will feed on to designing highly efficient solar cells and will lay the foundations for developing new high-speed nanoscale semiconductor devices.
The scale of opportunity: The fellowship will allow accelerated development of Advanced Functional Materials (AdvFM) through a detailed physical understanding leading to intelligent design of new materials. The HECS instrument developed during the fellowship will provide a new probe of the dynamic electronic properties of materials on the nanometre scale. In particular, with transistor feature sizes at now at the 7nm level, electronic probes on this length scales are likely to become increasingly important. AdvFMs have numerous applications including novel photovoltaic devices, displays, sensors, lasers, energy and data storage. The fellowship will concentrate on applications of AdvFMs in the area of third generation photovoltaics (PV). PV is an important area as one of greatest challenges facing us this century is the transition from a fossil-fuel based economy. The coming decade is likely to be disruptive for established players in the energy sector, but will produce many new technological and economic opportunities. It is important that the UK takes a lead in exploiting these opportunities for societal and economic reasons.
Economy: UK Manufacturing of HECS instruments would be a direct impact of the fellowship. While this would be highly specialised low-volume high-value manufacturing, the longer term opportunities enabled by the developments of third generation PV could have significant impact on large scale manufacturing and significant economic and societal benefit.
People: This project will play an important role in maintaining UKs competitiveness in surface science, ultrafast optics and advanced functional materials by providing a technical and scientific skills base. Researchers trained during the fellowship will provide an excellent conduit for passing the knowledge generated into wider industry.
Knowledge: This project is anticipated to advance the technology of nanoscale electrical measurements and PV. The transfer of solar cells materials knowledge to industry will aid the remarkable industrial advances and growth in the existing PV industry that have occurred over the last decade. This will ensure that the UK retains its lead in the science of new solar technologies and leads their industrialization.
Society: The project will impact the wider public through the advances in semiconductor technology that it will catalyze. For example, advances in solar technology offers huge societal benefit in terms of public and environmental health by accelerating our move away from polluting energy sources. Furthermore, integrated circuits with nanometre feature-size offer advantages in terms for higher speed and lower energy consumption, which will aid mobile applications and help curb the growing energy cost of data centres.