title: Direct and pulsed current annealing of p-MOSFET based dosimeter: the "MOSkin".
abstract: Contemporary radiation therapy (RT) is complicated and requires sophisticated real-time quality assurance (QA). While 3D real-time dosimetry is most preferable in RT, it is currently not fully realised. A small, easy to use and inexpensive point dosimeter with real-time and in vivo capabilities is an option for routine QA. Such a dosimeter is essential for skin, in vivo or interface dosimetry in phantoms for treatment plan verification. The metal-oxide-semiconductor-field-effect-transistor (MOSFET) detector is one of the best choices for these purposes, however, the MOSFETs sensitivity and its signal stability degrade after essential irradiation which limits its lifespan. The accumulation of positive charge on the gate oxide and the creation of interface traps near the silicon-silicon dioxide layer is the primary physical phenomena responsible for this degradation. The aim of this study is to investigate MOSFET dosimeter recovery using two proposed annealing techniques: direct current (DC) and pulsed current (PC), both based on hot charged carrier injection into the gate oxide of the p-MOSFET dosimeter. The investigated MOSFETs were reused multiple times using an irradiation-annealing cycle. The effect of the current-annealing parameters was investigated for the dosimetric characteristics of the recovered MOSFET dosimeters such as linearity, sensitivity and initial threshold voltage. Both annealing techniques demonstrated excellent results in terms of maintaining a stable response, linearity and sensitivity of the MOSFET dosimeter. However, PC annealing is more preferable than DC annealing as it offers better dose response linearity of the reused MOSFET and has a very short annealing time.
authors.affiliation: Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia.
authors.forename: Sami
authors.initials: S
authors.lastname: Alshaikh
authors.forename: Martin
authors.initials: M
authors.lastname: Carolan
authors.forename: Marco
authors.initials: M
authors.lastname: Petasecca
authors.forename: Michael
authors.initials: M
authors.lastname: Lerch
authors.forename: Peter
authors.initials: P
authors.lastname: Metcalfe
authors.forename: Anatoly
authors.initials: A
authors.lastname: Rosenfeld
mesh_terms: D019047:Phantoms, Imaging; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D012666:Semiconductors; D012825:Silicon
chemical_list: D012825:Silicon