Synthetic diamond for radiation detection applications
- Research Group
- Centre for Nuclear and Radiation Physics
- Techniques used
- Photolithography, thin film metal deposition
- Electrical and optical measurements
- Particle spectroscopy and X-ray induced current measurements
- Student will require
- an interest in radiation as well as semiconductor physics.
- to perform and develop experimental techniques and analysis, including small amounts of programming
- to conform with the institutional and departmental health and safety procedures, in particular, s/he is expected to use ionising radiation sources, lasers and/or chemicals if required by the project.
- to integrate into the radiation detector research group.
The student will fabricate and characterize detector test structures based on commercially available synthetic diamond produced by chemical vapour deposition. S/he will use departmental facilities including photolithography, metal deposition by sputtering and thermal evaporation for this purpose.
Subsequently, the electronic properties of the detectors -like charge carrier mobility and lifetime will be investigated and correlated to the detection performance under a variety of radiation sources.
The aim is to improve the current understanding of the fabrication parameters that crucially influence the device performance of diamond.
Diamond combines a number of unique properties which make it an interesting material for a variety of radiation detection applications, ranging from particle spectroscopy and neutron detection to fast timing applications and medical X-ray dosimetry, synchrotron beam monitoring and UV detection.
Diamonds mechanical and radiation hardness as well as its chemical resilience make it suitable for applications in environmentally challenging conditions, like high radiation fluxes, acidic environments etc. . In addition, due to its large electronic band gap, noise due to leakage currents can be minimized and devices are even operable at elevated temperatures. The large bandgap is also the reason for diamonds solar blindness. The material can achieve the highest charge carrier velocities of any semiconductor which results in very fast response times and excellent timing properties. Due to the low atomic number, it is relatively insensitive to γ- radiation and has thus a good sensitivity to particle radiation in γ - backgrounds, which is often advantageous in neutron detection scenarios.
Diamond is of interest for medical dosimetry due to the fact that its atomic number of Z=6 is much closer to the average atomic number of tissue than other established semiconductor materials and it offers a better spatial resolution than gas based ionisation chambers.
Similarly, beam monitors for high intensity X-ray synchrotron sources are interested in diamond due to its low Z too, as it minimizes the reduction of beam intensity by the device. Even in high fluxes, where the need for efficient heat dissipation becomes an issue, diamond excels with its heat conductivity that is five times higher even than copper.
Despite the fact that the potential and superiority of diamond for a wide range of detection applications has been demonstrated, it is not yet routinely used in many fields.
Its performance is mainly determined by the charge transport properties of the fabricated devices, which are determined by the quality (purity, crystal structure perfection) of bulk material as well as the electrode interfaces, which includes issues of surface quality (roughness, surface termination, polishing damage) and electrode deposition (for the electronic signal readout...). Bulk and surface defects of the devices result in unstable and non-reproducible detector signals - unfortunately, the origin of some of these effects is still not very well understood.
For more information, please contact Annika Lohstroh at A.Lohstroh@surrey.ac.uk.