Graphene integrated with semiconductor devices for high performance radiation detection

Radiation such as electromagnetic waves and subatomic particles is of vital importance to humans and living organisms as it can be harmful/fatal upon accidental or unconscious exposure, or it can be utilized to diagnose and cure diseases by a controlled exposure. Therefore, radiation detectors, which are devices that detect, quantify and identify radiation, are essential tools in medicine, environment, science and technology for protecting against the harm of radiation and/or making use of radiation in a controlled manner for its benefits. Even though various types of radiation detectors exist, innovative radiation detectors that offer superior detection performance and capabilities over the existing ones are needed for most applications. Graphene integrated with semiconductor devices for high performance radiation detection (GraSeRaD) was an ambitious and successful project which aimed to exploit graphene's high mobility for the development of radiation sensors. The project was a joint effort between UiO, NTNU and SINTEF and brought together material scientists, physicists and electrical engineers. Researchers were tasked with two main research topics: the development of x-ray detectors and the growth of graphene on semiconductor surfaces. In order to develop x-ray detectors, the radiation hardness graphene to gamma and proton irradiation was investigated. Real x-ray detectors were fabricated and their response to x-rays characterized. Graphene was grown on metallic surfaces and then on semiconductor surfaces avoiding the need for transfer processes which contaminate and degrade graphene's quality. GraSeRaD enabled the research team to develop significant and world class competence in graphene growth and material characterization, graphene device fabrication, graphene transfer techniques and sensor characterization. The project also helped to foster collaboration with world leading groups around the world including Japan, China, Australia, Germany, Denmark, Sweden, United Kingdom and the USA.

GraSerad has led to the following outcome based on the project results Developed know how in the fabrication of high-performance graphene and 2-D material based transistors based on world leading encapsulation and fabrication techniques at Nanolab facilities (Minalab and Nanolab). Specific competence in the characterization of graphene transistors and their subsequent use as x-ray detectors Know how on the growth techniques of graphene on semiconductor surfaces Collaboration with synchrotron facilities around the world including Astrid Aarhus, Synchrotron Light Research Institute Thailand, MAX IV Sweden, Australian Synchrotron, Melbourne and Bessy II Berlin. The project has also led to a deep scientific collaboration with Kansas State University, Sandia National Laboratories and Nanjing University with the exchange of samples and scientists over the project period.

This research project pursues an innovative approach to radiation detection by integrating graphene with semiconductor devices and exploiting some exceptional electronic properties of graphene such as super-high carrier mobility and ultra-high sensitivity of graphene's conductivity to even tiny changes in local charge or electric field. This novel detection concept can lead to excellent radiation detection performance such as very high energy resolution, ultra-high detection speed, and low operation voltage, providing unique solutions to many limitations of the existing detector technologies. The findings of the project will potentially have a great impact in applications including, but not limited to, environmental monitoring, waste management, medical imaging and hadron therapy. There are a number of challenges associated with the realization of graphene-based radiation detectors such as i) growth of high quality large area graphene films ii) scalable integration of graphene with different semiconductor materials/devices, iii) characterization and optimization of the graphene to semiconductor interface to ensure optimal conditions for radiation sensing, iv) sensor design and fabrication, and v) sensor operation, readout, and characterization of the signal. GraSeRaD will address all these challenges by bringing together people with required expertise from material science, condensed matter physics, radiation sensors, detector readout electronics, radiation physics, and potential end users from a variety of fields and by utilizing the existing advanced infrastructure and facilities in Norway.