Low-Operating-Voltage Operation and Improvement in Sensitivity With Passivated OFET Sensors for Determining Total Dose Radiation

Raval, Harshil N.; Rao, V. Ramgopal

doi:10.1109/led.2010.2074179

Cited by 19 publications

(8 citation statements)

References 15 publications

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“…Passive sensors rely on the detection of changes induced in the sample upon exposure to radiation and that persist after exposure; on the contrary, active sensors monitor in real time by recording the photoconductive gain. [ 26 ] In this case, a passive detection ensures that the irradiation and device testing take place sequentially, i.e., there is no voltage applied to the RAD‐OFET while it is placed on a patient.…”

Section: Figurementioning

confidence: 99%

Organic Field‐Effect Transistors as Flexible, Tissue‐Equivalent Radiation Dosimeters in Medical Applications

et al. 2020

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Radiation therapy is one of the most prevalent procedures for cancer treatment, but the risks of malignancies induced by peripheral beam in healthy tissues surrounding the target is high. Therefore, being able to accurately measure the exposure dose is a critical aspect of patient care. Here a radiation detector based on an organic field‐effect transistor (RAD‐OFET) is introduced, an in vivo dosimeter that can be placed directly on a patient's skin to validate in real time the dose being delivered and ensure that for nearby regions an acceptable level of low dose is being received. This device reduces the errors faced by current technologies in approximating the dose profile in a patient's body, is sensitive for doses relevant to radiation treatment procedures, and robust when incorporated into conformal large‐area electronics. A model is proposed to describe the operation of RAD‐OFETs, based on the interplay between charge photogeneration and trapping.

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Section: Figurementioning

confidence: 99%

Organic Field‐Effect Transistors as Flexible, Tissue‐Equivalent Radiation Dosimeters in Medical Applications

et al. 2020

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“…The electrical characterization of the OFETs was carried out on a probe-station using Keithley 2602 SMUs in ambient conditions. It has been already reported that passivation layer of silicon nitride on top of the samples avoids the degradation of organic semiconducting materials in ambient [3][4][5]11]. The OFETs were then exposed to different doses of -radiation, using Cobalt -60 radiation source by varying the time of exposure, and electric characteristics were obtained after each exposure by measuring the drain to source current (I DS ) by varying gate voltage (V GS ) from 0 to -30 V at a constant drain to source voltage (V DS ) of -30 V (I DS -V GS characteristics).…”

Section: Pentacene and P3ht Based Ofets As Sensors For Ionizing Radiamentioning

confidence: 99%

“…These organic electronic sensors also offer various advantages, such as, low cost manufacturing and large area coverage with flexible substrates. Pentacene and P3HT are widely used p-type organic semiconducting materials for various organic electronic applications [8][9][10] and were also reported by us as sensors for ionizing radiation [3][4][5]. In this work, the change in the conductivity of the thin-films of pentacene and P3HT, upon exposure to ionizing radiation, was studied using EFM imaging technique.…”

Section: Introductionmentioning

confidence: 97%

“…Organic semiconducting materials are being explored for various sensing applications as their material properties change upon interaction with various chemicals, gases, chemical vapors and high energy ionizing radiation [1][2][3][4][5][6][7]. These organic electronic sensors also offer various advantages, such as, low cost manufacturing and large area coverage with flexible substrates.…”

Section: Introductionmentioning

confidence: 99%

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OFET Sensors with Poly 3-hexylthiophene and Pentacene as Channel Materials for Ionizing Radiation

Raval

Rao

2012

MRS Proc.

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Pentacene and poly 3-hexylthiophene (P3HT) are the most promising p-type organic semiconducting materials for fabrication of organic field effect transistors (OFETs). OFETs with aforesaid organic semiconducting materials have been demonstrated as total dose detectors for ionizing radiation, wherein the changes in the electrical characteristic parameters, such as, increase in the OFF current, increase in the ON current, change in the current ratio, shift in the threshold voltage, change in the subthreshold swing, etc., were used as a measure of ionizing radiation dose. Upon exposure to ionizing radiation P3HT based OFET sensor has shown an OFF current sensitivity of 4.4 nA/Gy while pentacene based OFET sensor has shown an OFF current sensitivity of 26.7 nA/Gy for a total of 50 Gy dose of ionizing radiation. Change in the conductivity of the thin-films of pentacene and P3HT were observed and compared using electrostatic force microscopy (EFM) imaging before and after exposure to ionizing radiation. Effects of ionizing radiation on the energy band structures of the organic semiconducting materials, pentacene and P3HT, have been studied using UV-visible spectroscopy. Moreover, analysis of UV-visible spectra of the thin-films suggested the generation of energy states in larger quantity in case of pentacene thin-film as compared to P3HT thin-film upon exposure to the same dose of ionizing radiation. These results confirm the higher sensitivity observed in pentacene OFET sensor as compared to P3HT OFET sensor in terms of the change in electrical parameters.

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“…The thin-film of silicon nitride as a passivation layer has been reported earlier by us to avoid any degradation due to gases and moisture in the air [5,6]. The CuPc thin-film resistor was prepared on a silicon wafer where a thick (>500 nm) SiO2 was grown using a wet oxidation process to isolate the silicon wafer from the electrodes.…”

Section: Cupc Organic Electronic Devices As Radiation Sensorsmentioning

confidence: 99%

Copper (II) Phthalocyanine Based Field Effect Transistors as Total Dose Sensors for Determining Ionizing Radiation Dose

Raval

Rao

2012

MRS Proc.

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Changes in the material properties of copper (II) phthalocyanine (CuPc) thin-films were studied upon exposure to increasing dose of ionizing radiation using photoluminescence spectrum. We observe generation of new energy states below the band gap upon exposure to ionizing radiation. Organic electronic devices -CuPc based resistor and an organic field effect transistor (OFET) -are proposed in this work as total dose sensors for ionizing radiation. We observe an increase in the conductivity of CuPc thin-films with increasing dose of ionizing radiation. To overcome the possibility of changes/degradation in the electrical properties of CuPc thin-films upon interaction with various gases and moisture in the environment, a passivation layer of silicon nitride, deposited by hot-wire CVD process is proposed. Effect of ionizing radiation on the electrical properties of thin-films of CuPc has been studied. We observe a 170% increase in the resistance of the thin-film for a total of 50 Gy radiation dose using Cobalt-60 (60Co) radiation source. Moreover, significant changes in the electrical characteristics of an OFET, with CuPc as an organic semiconductor, have been observed with increasing doses of ionizing radiation. Experiments with an OFET (W/L = 19350 μm / 100 μm and tox = 150 nm) as a sensor resulted in a ~100X change in the OFF current for a total of 50 Gy dose of ionizing radiation exhibiting a sensitivity of ~1 nA/Gy. Moreover, implementing a reader circuit, shift in the threshold voltage of the OFET at 1e-7 A drain current displayed a sensitivity of 80 mV/Gy for a total of 50 Gy dose of ionizing radiation. CuPc based organic electronic devices have advantages as sensors because of their low-cost fabrication, large area coverage on flexible substrates, etc.

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Low-Operating-Voltage Operation and Improvement in Sensitivity With Passivated OFET Sensors for Determining Total Dose Radiation

Cited by 19 publications

References 15 publications

Organic Field‐Effect Transistors as Flexible, Tissue‐Equivalent Radiation Dosimeters in Medical Applications

Organic Field‐Effect Transistors as Flexible, Tissue‐Equivalent Radiation Dosimeters in Medical Applications

OFET Sensors with Poly 3-hexylthiophene and Pentacene as Channel Materials for Ionizing Radiation

Copper (II) Phthalocyanine Based Field Effect Transistors as Total Dose Sensors for Determining Ionizing Radiation Dose

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