2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2014
ABSTRACT Epitaxial Silicon Carbide Schottky devices were characterized with the aim of using them... more ABSTRACT Epitaxial Silicon Carbide Schottky devices were characterized with the aim of using them for neutron detection at elevated temperatures. Current Voltage (I/V), capacitance Voltage (C/V) and alpha spectroscopy measurements were carried out at temperatures up to 500K. The resistivity dependance on temperature follows an exponential behaviour with an activation energy of 0.15meV. Ideality factor show a linear decrease with temperature up to 400 K and Schottky barrier height decreases with increasing temperature. Charge collection efficiency approaches 90% at 100V for most temperatures except for 500 K which shows a 5% reduction. Signal stability of the material and leakage current appear to improve with time, and in particular the leakage current stabilises faster at higher temperatures. These results indicate good charge transport behaviour and exceptional stability of the devices and so are expected to provide good detection performance of thermal neutrons (using convertor layers) in harsh radiation media.
Silicon carbide and diamond semiconductor neutron detectors have been analyzed for potential use ... more Silicon carbide and diamond semiconductor neutron detectors have been analyzed for potential use in active interrogation security applications. Epitaxial silicon carbide, bulk semi-insulating silicon carbide, electronic grade single crystal diamond and polycrystalline diamond were all individually irradiated with alpha (Am-241), x-ray (ISO 4037 Narrow), gamma (Cs-137, Co-60) and neutron (Cf-252, AmBe, Mono-energetic) radiation over a wide range of dose rates. These were compared against a commercial Hamamasu silicon PIN photodiode, type S1223-01. As well as observing the acquired spectra for each radiation and dose rate, the polarisation rate of the detectors (the stability of the spectra with time) was measured. Results demonstrated the ability of each material to directly detect fast neutron radiation, and distinguish that neutron response from potential ionising photon radiation fields, over a wide range of dose rates. It was shown that this ability to simply discriminate between...
... Mohamed AE Abdel-Rahman*, Annika Lohstroh, and Paul J. Sellin ... is fixed on the top contact... more ... Mohamed AE Abdel-Rahman*, Annika Lohstroh, and Paul J. Sellin ... is fixed on the top contact of each device using a 4124 Ball Bonder and the other end connected to a separate copper pad on the top layer of the ceramic substrate which is then soldered to the read out cable. ...
Real time imaging of the electric field distribution in CZT at low temperature has been carried o... more Real time imaging of the electric field distribution in CZT at low temperature has been carried out using the Pockels electro-optical effect. CZT detectors have been observed to show degraded spectroscopic resolution at low temperature due to so-called ‘polarization’ phenomena. By mounting a CZT device in a custom optical cryostat, we have used Pockels imaging to observe the distortion of the electric field distribution in the temperature range 240K - 300K. At 240K the electric field has a severely non-uniform depth distribution, with a high field region occupying ∼10% of the depth of the device under the cathode electrode and a low field in the remainder of the device. Using an alpha particle source positioned inside the vacuum chamber we have performed simultaneous alpha particle transient current (TCT) measurements. At low temperatures the alpha particle current pulses become significantly shorter, consistent with the reduced electron drift time due to a non-uniform electric fiel...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2004
The first implementation of digital ion-beam-induced charge (IBIC) imaging is presented, which pe... more The first implementation of digital ion-beam-induced charge (IBIC) imaging is presented, which permits spectroscopic time-resolved IBIC imaging of charge transport in semiconductors. A digital IBIC system has been developed which uses a high-speed waveform digitiser to capture the pulse shapes produced by interactions of a 1μm resolution scanning microbeam in semiconductor samples. Using a variety of digital pulse shape analysis algorithms, quantitative images of charge signal amplitude, charge carrier lifetime, mobility and trapping phenomena can be acquired in real-time, with a time resolution of <20ns. We report data from the commissioning experiment which shows digital IBIC images of electron and hole transport in CdZnTe radiation detectors, obtained by lateral scanning of the ion beam between the cathode and anode. The room temperature electron drift mobility in CdZnTe was measured with a value of 1.1×103cm2/Vs.
2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2014
ABSTRACT Epitaxial Silicon Carbide Schottky devices were characterized with the aim of using them... more ABSTRACT Epitaxial Silicon Carbide Schottky devices were characterized with the aim of using them for neutron detection at elevated temperatures. Current Voltage (I/V), capacitance Voltage (C/V) and alpha spectroscopy measurements were carried out at temperatures up to 500K. The resistivity dependance on temperature follows an exponential behaviour with an activation energy of 0.15meV. Ideality factor show a linear decrease with temperature up to 400 K and Schottky barrier height decreases with increasing temperature. Charge collection efficiency approaches 90% at 100V for most temperatures except for 500 K which shows a 5% reduction. Signal stability of the material and leakage current appear to improve with time, and in particular the leakage current stabilises faster at higher temperatures. These results indicate good charge transport behaviour and exceptional stability of the devices and so are expected to provide good detection performance of thermal neutrons (using convertor layers) in harsh radiation media.
Silicon carbide and diamond semiconductor neutron detectors have been analyzed for potential use ... more Silicon carbide and diamond semiconductor neutron detectors have been analyzed for potential use in active interrogation security applications. Epitaxial silicon carbide, bulk semi-insulating silicon carbide, electronic grade single crystal diamond and polycrystalline diamond were all individually irradiated with alpha (Am-241), x-ray (ISO 4037 Narrow), gamma (Cs-137, Co-60) and neutron (Cf-252, AmBe, Mono-energetic) radiation over a wide range of dose rates. These were compared against a commercial Hamamasu silicon PIN photodiode, type S1223-01. As well as observing the acquired spectra for each radiation and dose rate, the polarisation rate of the detectors (the stability of the spectra with time) was measured. Results demonstrated the ability of each material to directly detect fast neutron radiation, and distinguish that neutron response from potential ionising photon radiation fields, over a wide range of dose rates. It was shown that this ability to simply discriminate between...
... Mohamed AE Abdel-Rahman*, Annika Lohstroh, and Paul J. Sellin ... is fixed on the top contact... more ... Mohamed AE Abdel-Rahman*, Annika Lohstroh, and Paul J. Sellin ... is fixed on the top contact of each device using a 4124 Ball Bonder and the other end connected to a separate copper pad on the top layer of the ceramic substrate which is then soldered to the read out cable. ...
Real time imaging of the electric field distribution in CZT at low temperature has been carried o... more Real time imaging of the electric field distribution in CZT at low temperature has been carried out using the Pockels electro-optical effect. CZT detectors have been observed to show degraded spectroscopic resolution at low temperature due to so-called ‘polarization’ phenomena. By mounting a CZT device in a custom optical cryostat, we have used Pockels imaging to observe the distortion of the electric field distribution in the temperature range 240K - 300K. At 240K the electric field has a severely non-uniform depth distribution, with a high field region occupying ∼10% of the depth of the device under the cathode electrode and a low field in the remainder of the device. Using an alpha particle source positioned inside the vacuum chamber we have performed simultaneous alpha particle transient current (TCT) measurements. At low temperatures the alpha particle current pulses become significantly shorter, consistent with the reduced electron drift time due to a non-uniform electric fiel...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2004
The first implementation of digital ion-beam-induced charge (IBIC) imaging is presented, which pe... more The first implementation of digital ion-beam-induced charge (IBIC) imaging is presented, which permits spectroscopic time-resolved IBIC imaging of charge transport in semiconductors. A digital IBIC system has been developed which uses a high-speed waveform digitiser to capture the pulse shapes produced by interactions of a 1μm resolution scanning microbeam in semiconductor samples. Using a variety of digital pulse shape analysis algorithms, quantitative images of charge signal amplitude, charge carrier lifetime, mobility and trapping phenomena can be acquired in real-time, with a time resolution of <20ns. We report data from the commissioning experiment which shows digital IBIC images of electron and hole transport in CdZnTe radiation detectors, obtained by lateral scanning of the ion beam between the cathode and anode. The room temperature electron drift mobility in CdZnTe was measured with a value of 1.1×103cm2/Vs.
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