Determining ionizing radiation using sensors based on organic semiconducting material

Abstract

The use of organic semiconducting material sensors as total dose radiation detectors is proposed, wherein the change in conductivity of an organic material is measured as a function of ionizing radiation dose. The simplest sensor is a resistor made using organic semiconductor. Furthermore, for achieving higher sensitivity, organic field effect transistor ͑OFET͒ is used as a sensor. A solution processed organic semiconductor resistor and an OFET were fabricated using poly 3-hexylthiophene ͑P3HT͒, a p-type organic semiconductor material. The devices are exposed to Cobalt-60 radiation for different total dose values. The changes in electrical characteristics indicate the potential of these devices as radiation sensors.

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

“…The increase in the conductivity of the material tends to increase the I ON . On the other hand, upon irradiation, there is interface trap generation at the gate oxide-organic semiconductor interface [7] and trapping occurring in the gate oxide which degrades the carrier mobility significantly, owing to increased scattering of the charge carriers, as commonly observed in MOS-like devices [13], [14]. Because of these two competing mechanisms, the change in I ON is quite different as compared to that of I OFF behavior, with increasing dose of radiation.…”

“…1(c) for different total dose radiation values. As was shown by us earlier, due to the high energy 60 Co radiation, some of the thiophene molecules in the chain get oxidized, and the appearance of these oxidized states results in a higher 0741-3106/$26.00 © 2010 IEEE conductivity of the material [7], [11], [12]. The rate of generation of oxidized states is not linear but saturating with increasing radiation dose.…”

“…As can be observed in Table III, the I OFF for a sensor with three OFETs connected in parallel was found more than three times the I OFF for a single-OFET sensor due to its larger area and overlap. The changes caused due to radiation are permanent in nature, and the effect is irreversible, as discussed in [7]. The changes in the electrical characteristics show a good stability, making these sensors useful for determining total dose radiation for field applications.…”

“…Applications of organic semiconducting material device sensors for determining ionizing radiation and detection based on changes in various electrical parameters were also reported [7], wherein the change in conductivity of an organic material was measured as a function of ionizing radiation using an organic semiconductor-based resistor and an organic field-effect transistor (OFET). In this letter, the use of a high-k dielectric material in the gate stack for achieving low-operating-voltage operation, improvement in the sensor stability with a passivation technique, and an array configuration for enhancing the sensitivity of these structures are explored for dosimetry applications.…”

Bias-Stress-Induced Instability of Polymer Thin-Film Transistor Based on Poly(3-Hexylthiophene)

“…INTRODUCTION I N RECENT years, conjugated polymers have gained increasing interest as the active material in organic thin-film transistors (TFTs) due to their good performance proven with low-temperature processing on a flexible substrate. Among these materials, poly(3-hexylthiophene) (P3HT) has received considerable attention due to its relatively high carrier mobility for low-cost low-power large-area electronic systems such as organic displays [1], sensors [2], and complementary circuits [3]. Great progress has been made to develop high-performance polymer TFTs (PTFTs) over the past decade [4], [5].…”