Picture of mobile phone running fintech app

Fintech: Open Access research exploring new frontiers in financial technology

Strathprints makes available Open Access scholarly outputs by the Department of Accounting & Finance at Strathclyde. Particular research specialisms include financial risk management and investment strategies.

The Department also hosts the Centre for Financial Regulation and Innovation (CeFRI), demonstrating research expertise in fintech and capital markets. It also aims to provide a strategic link between academia, policy-makers, regulators and other financial industry participants.

Explore all Strathclyde Open Access research...

Developments in GaAs pixel detectors for X-ray imaging

Bates, R and Campbell, M and Da Via, C and Heijne, E and Heuken, M and Jurgensen, H and Ludwig, J and Manolopoulos, S and Marder, D and Mathieson, K and O'Shea, V and Raine, C and Rogalla, M and Smith, KM (1998) Developments in GaAs pixel detectors for X-ray imaging. In: IEEE Transactions on Nuclear Science: proceedings of the 44th IEEE Nuclear Science Symposium and Medical Imaging Conference. IEEE, New York, pp. 534-540. ISBN 0780342593

Full text not available in this repository. Request a copy from the Strathclyde author

Abstract

Position sensitive hybrid pixel detectors have been fabricated by bump bonding silicon or bulk grown semi-insulating gallium arsenide pixel detectors to CMOS read-out chips. Their performance as X-ray Imaging sensors, in the energy range of 10-70 keV, was evaluated in terms of spatial resolution. For the GaAs device a fit was made to the line spread function (LSF) obtained from the image of a narrow slit and the corresponding modulation transfer function (MTF) and noise equivalent passband (N-e) evaluated. A value of 5.7 line pairs per mm (lp/mm) was found for the latter, with a modulation of 10% at the Nyquist frequency (N-y). A comparison is also given of the performance of these devices with state-of-the-art scintillator on silicon CCD dental X-ray sensors. In a bid to improve detector performance, thick layers of high quality GaAs have recently been grown by low pressure vapour phase epitaxy (LP-VPE). Hall measurements on initial samples gave free carrier concentration of 1-8 x 10(11) cm(-3). From the C-V dependence of a reverse-biased Schottky diode this material, however, a space charge density of 2 x 10(13) cm(-3) was measured. The observed temperature and frequency dependency of the capacitance is characteristic of the presence of deep levels and so the material is believed to have a small degree of compensation due to these levels. The measured charge collection efficiency determined (c.c.e) for 60 keV gamma rays showed an increase with reverse bias, reaching a plateau value of 93% for 100V. The limitations of present detectors are discussed and possible future developments indicated.