Contatto di riferimento: Ilaria Fratelli
Partecipanti: Dr.ssa Ilaria Fratelli
Abstract
Distributed X-ray radiation dosimetry is crucial in diverse security areas with strong environment and human impact such as nuclear waste management, radiotherapy or radioprotection devices.
Many devices dedicated to the radiation dosimetry have been studied and realized during the past decades working on different kind of interaction between the ionizing radiation and materials. Several dose range and energy range can be monitored by different devices.
Here I will present a fast, real time dosimetry detection system based on flexible oxide thin film transistors that show a quantitative shift in threshold voltage of up to 3.4 V/Gy upon exposure to ionizing radiation. The transistors employ Indium-Gallium-Zinc-Oxide as semiconductor and a multilayer dielectric based on Silicon Oxide and Tantalum Oxide. The measurements demonstrate that the threshold voltage shift is caused by the accumulation of positive ionization charge in the dielectric layer due to high-energy photon absorption in the high-Z dielectric. The novel dielectric structure implemented in this thin film transistors allows the improvement of the detector sensitivity of one order of magnitude compared with the standard RADFET performance.
Besides, the high mobility combined with a steep sub-threshold slope of the transistor allows for fast, reliable and ultra-low power readout of the deposited radiation dose. In fact, the order of magnitude variation in transistor channel impedance upon exposure to radiation makes it possible to employ a low-cost, passive RFID sensor tag for its readout. I will present the results coming from the realization of a passive, programmable, wireless sensor that reports in real-time the excess of critical radiation doses.