Sensitivity of RADFET for gamma and X-ray doses used in medicine

In this paper, the results of radiation sensitive field effect transistors (Al-gate p-channel metal-oxide-semiconductor field effect transistors) sensitivity to gamma and X-ray irradiation are presented. Radiation fields were created using 60Co source for three dose ranges (0-1 Gy, 0-5 Gy, and 0-50 Gy), as well as X-ray unit of 280 kVp spectrum for a single dose range from 0 to 5 Gy. The sensitivity was characterized by the threshold voltage shift, determined from reader circuit measurements, as a function of absorbed radiation dose. It was shown that for the three dose ranges of gamma radiation, as well as for the X-ray range from 0 Gy to 5 Gy there is approximately a linear dependence between threshold voltage shift DVT and radiation dose D. The application of positive bias of +5 V at the RADFET gate during irradiation, for these ranges of gamma radiation, also for X-ray dose range, leads to the increase in DVT and also, approximately a linear dependence between DVT and D, is established. Moreover, it was shown that the sensitivity of RADFET is much higher in the case of X-ray irradiation then in the case of gamma-ray irradiation for the same dose range.

Download Full-text

Application of pMOS dosimeters in low-field mode for radiation dose measurements which could be used in radiotherapy

Nuclear Technology and Radiation Protection ◽

10.2298/ntrp1604349p ◽

2016 ◽

Vol 31 (4) ◽

pp. 349-355 ◽

Cited By ~ 3

Author(s):

Svetlana Pejovic ◽

Momcilo Pejovic ◽

Dragan Stojanov

Keyword(s):

Radiation Dose ◽

Gamma Rays ◽

Threshold Voltage ◽

Dose Range ◽

Field Mode ◽

Threshold Voltage Shift ◽

Voltage Shift ◽

X Ray ◽

Low Field ◽

Absorbed Radiation Dose

The pMOS dosimeters sensitivity (Tyndall National Institute, Cork, Ireland) to gamma and X-ray irradiation and 2000 h fading at room temperature is presented. The radiation fields were created using a 60Co source for two dose ranges (1-5 Gy and 10-50 Gy) as well as for X-ray units of a 280 kV spectrum for a single dose range from 0.1 to 1 Gy. Irradiation was performed in low-field mode (no gate bias during irradiation, Virr = 0 V), sensitivity characterized by the threshold voltage shift as a function of the absorbed radiation dose and time after irradiation. Linear dependence between the threshold voltage shift and the absorbed radiation dose was only established for pMOS dosimeters which were irradiated by gamma rays in the dose range of 1 to 5 Gy. Obtained results show that the sensitivity of these components is much higher in case of X-ray radiation than in that of gamma ray radiation. Moreover, the fading of irradiated pMOS dosimeters with X-rays is higher than in the ones irradiated with gamma rays.

Download Full-text

Threshold-Voltage-Shift Mechanism in Pentacene Field Effect Transistors Caused by Photoirradiation

Japanese Journal of Applied Physics ◽

10.1143/jjap.47.3189 ◽

2008 ◽

Vol 47 (4) ◽

pp. 3189-3192 ◽

Cited By ~ 8

Author(s):

Chang Bum Park ◽

Takamichi Yokoyama ◽

Tomonori Nishimura ◽

Koji Kita ◽

Akira Toriumi

Keyword(s):

Threshold Voltage ◽

Field Effect ◽

Field Effect Transistors ◽

Threshold Voltage Shift ◽

Voltage Shift

Download Full-text

The gamma-ray irradiation sensitivity and dosimetric information instability of RADFET dosimeter

Nuclear Technology and Radiation Protection ◽

10.2298/ntrp1304415p ◽

2013 ◽

Vol 28 (4) ◽

pp. 415-421 ◽

Cited By ~ 7

Author(s):

Milic Pejovic

Keyword(s):

Threshold Voltage ◽

Field Effect ◽

Room Temperature ◽

Gamma Ray ◽

Field Effect Transistors ◽

Metal Oxide Semiconductor ◽

Oxide Semiconductor ◽

Threshold Voltage Shift ◽

Voltage Shift ◽

Gamma Ray Irradiation

The gamma-ray irradiation sensitivity to radiation dose range from 0.5 Gy to 5 Gy and post-irradiation annealing at room and elevated temperatures have been studied for p-channel metal-oxide-semiconductor field effect transistors (also known as radiation sensitive field effect transistors or pMOS dosimeters) with gate oxide thicknesses of 400 nm and 1 mm. The gate biases during the irradiation were 0 and 5 V and 5 V during the annealing. The radiation and the post-irradiation sensitivity were followed by measuring the threshold voltage shift, which was determined by using transfer characteristics in saturation and reader circuit characteristics. The dependence of threshold voltage shift DVT on absorbed radiation dose D and annealing time was assessed. The results show that there is a linear dependence between DVT and D during irradiation, so that the sensitivity can be defined as DVT/D for the investigated dose interval. The annealing of irradiated metal-oxide-semiconductor field effect transistors at different temperatures ranging from room temperature up to 150?C was performed to monitor the dosimetric information loss. The results indicated that the dosimeters information is saved up to 600 hours at room temperature, whereas the annealing at 150?C leads to the complete loss of dosimetric information in the same period of time. The mechanisms responsible for the threshold voltage shift during the irradiation and the later annealing have been discussed also.

Download Full-text