Monday 28 March 2011, 3.15PM
Speaker(s): Dr Annika Lohstroh, University of Surrey
Dr Annika Lohstroh, Department of Physics, University of Surrey (part of the South East Physics Network (SEPNet), UK)
Diamond and Silicon carbide have attracted interest for ionising radiation and UV detector applications for many decades due to a unique combination of advantages in their bulk material properties. In particular, their large band gap results in low leakage currents observed in dark conditions, even at elevated temperatures. Their low atomic number minimises absorption of X- and g-rays compared to most other common semiconductor detector materials, which is desirable in their application as neutron detectors. In addition, the large heat conductivity and the ability to produce thin free standing films of the material also make them suitable as on-line X-ray beam monitors in high intensity beams for example in synchrotron environments. Diamond is also a candidate for medical dosimetry applications, as its atomic number is close to some common types of tissue and its large charge carrier mobilities have attracted interest for timing applications. Both materials are very hard, which implies radiation hardness and offers longer expected device life times even under extreme radiation conditions.
However, charge transport across the electrical contact/bulk interface and limitations of charge transport due to residual bulk defects are still not completely understood and controlled. Charge trapping can lead to the development of space charge in the devices which will modify the velocity of the charge carriers and hence the signal current of the detectors. The effect of this space charge can remain over long timescales (in the order of days). The presentation will give an introduction to signal formation in direct solid state radiation detectors and an overview of our bulk characterisation of charge transport properties in SiC and diamond. In addition, our recent studies of diamond in timing and dosimetry applications and SiC for neutron detection will also be discussed.