Very recently we have shown that organic semiconducting single crystals (OSSCs) can be used as effective direct X-ray detectors [1]. In particular, devices based on solution-grown OSSCs, 4-hydroxycyanobenzene (4HCB) (Figure 1a), have been fabricated and operated in air, under ambient light and at room temperature, delivering well reproducible performances and a stable linear response to the X-ray dose rate, with notable radiation hardness and resistance to aging. In these experiments a molybdenum tube at 35keV was used as x-rays source; molybdenum has an x-ray spectrum with first a dominant peak at 17.9 keV, a secondary peak at 19.5 keV and a not negligible energy broad tail up to 35keV, due to bremsstrahlung radiation. The modulation of the filament current allows to reach 25mGy/s as minimum dose rate, but this value is too high for most kinds of dosimetric and medical applications. Driving voltages as low as 50 V, in unoptimized devices, were sufficient to obtain linear responses. A notable radiation hardness and resistance to aging was also found. The role played by metal contacts on the detector response has been investigated, leading to the fabrication of fully organic, optically transparent devices, characterized by good performances. In a previous beamtime on SYRMEP [2], we operated a full characterization of the electrical response of the above mentioned OSSCs-based detectors irradiated with X-rays at different energies (10-30 keV) and doses, relevant for dosimetric and security applications. In this range a good linearity of the device at dose rates between 1 and 170 mGy/s was found, with sensitivities up to 0.05 nC/mGy for energy around 15-17 keV, confirming the possibility to use OSSCs as a new family of direct organic detectors.
Esperimento 20125420 presso Sincrotrone ELETTRA Trieste, sulla beamline SYRMEP sul tema “Time-resolved and space-resolved studies of the electrical response to X-rays of organic semiconducting single crystals ”
FRABONI, BEATRICE
2013
Abstract
Very recently we have shown that organic semiconducting single crystals (OSSCs) can be used as effective direct X-ray detectors [1]. In particular, devices based on solution-grown OSSCs, 4-hydroxycyanobenzene (4HCB) (Figure 1a), have been fabricated and operated in air, under ambient light and at room temperature, delivering well reproducible performances and a stable linear response to the X-ray dose rate, with notable radiation hardness and resistance to aging. In these experiments a molybdenum tube at 35keV was used as x-rays source; molybdenum has an x-ray spectrum with first a dominant peak at 17.9 keV, a secondary peak at 19.5 keV and a not negligible energy broad tail up to 35keV, due to bremsstrahlung radiation. The modulation of the filament current allows to reach 25mGy/s as minimum dose rate, but this value is too high for most kinds of dosimetric and medical applications. Driving voltages as low as 50 V, in unoptimized devices, were sufficient to obtain linear responses. A notable radiation hardness and resistance to aging was also found. The role played by metal contacts on the detector response has been investigated, leading to the fabrication of fully organic, optically transparent devices, characterized by good performances. In a previous beamtime on SYRMEP [2], we operated a full characterization of the electrical response of the above mentioned OSSCs-based detectors irradiated with X-rays at different energies (10-30 keV) and doses, relevant for dosimetric and security applications. In this range a good linearity of the device at dose rates between 1 and 170 mGy/s was found, with sensitivities up to 0.05 nC/mGy for energy around 15-17 keV, confirming the possibility to use OSSCs as a new family of direct organic detectors.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
