High precision resistive temperature sensors have the advantages of high stability, fast response speed, and simple manufacturing, and play an important role in daily life. However, traditional channel materials such as platinum are severely limited in their development due to their high cost and low initial resistance. In the past few decades, reduced graphene oxide (rGO) has received widespread attention as a promising alternative to traditional materials due to its extreme specific surface area and various optional surface chemical properties. Graphene oxide (GO) is an insulator, however, the sheet resistance of reduced graphene oxide (i.e. reduced graphene oxide) can be reduced by several orders of magnitude, thereby transforming the material into a semiconductor or even a graphene like semimetal. The prepared rGO temperature sensor exhibits negative temperature coefficient thermistor characteristics, with a wide operating temperature range and high sensitivity.

There are many methods for preparing temperature sensors by reducing graphene oxide, such as thermal reduction, chemical reduction, and laser reduction. The rGO temperature sensor prepared by Sehrawat et al. in 2018 through thermal reduction showed a temperature coefficient of resistance (TCR) of 0.801%/℃ in the temperature range of 30 ℃ to 100 ℃, with a response time of 52 seconds. However, the thermal reduction method inevitably requires higher temperatures, which may cause damage to other electronic devices integrated into sensors in practical applications. The ultrafast rGO temperature sensor prepared by Sahoo et al. using chemical reduction method has a response time of 0.59 s and a recovery time of 7.22 s. However, in chemical reduction, highly toxic reducing agents are required during the reduction process, which is not very environmentally friendly. At the same time, laser beam reduction GO (LIG) technology has recently been developed to achieve single step patterned rGO production. Although this method is much superior to traditional methods, such as direct patterning, no additional post lithography steps are required to manufacture patterned rGO, only operation under environmental conditions, and high production yield, its lower sensitivity (0.142%/℃) and micrometer level pattern spacing hinder its application in a wider range of fields. As an alternative, electron

beam irradiation (EBI) induced rGO has the potential to upgrade this technology to temperature sensors with higher device density and better sensitivity.

The interaction between high-energy electrons and matter ionizes and excites molecules of various substances, triggering chemical reactions. Therefore, the use of highly focused electron beams can achieve the reduction of GO at the micrometer or even nanometer scale. Usually, certain processes that cannot be achieved through heat treatment or optical treatment can be achieved through electron beam irradiation. As the most promising method for preparing nanoscale rGO, electron beam irradiation has the characteristics of non toxicity, no chemical composition, high efficiency, and high tunability. However, research on the reduction technology and mechanism of graphene oxide based on EBI is just beginning.

Here, we conducted a systematic study on electron beam reduction of GO under different electron beam doses and electron beam energies. Research has found that within the temperature range of 30 ℃ to 80 ℃, TCR decreases monotonically with increasing electron beam dose, from 1.34%/℃ to 0.59%/℃. Based on these results, the TCR value of the rGO based temperature sensor reached 1.18%/℃, with a response time of only 0.17 seconds. Compared with other methods of preparing rGO temperature sensors, the rGO temperature sensor prepared by EBI technology has a wider TCR variation range and shorter response time.

Source: Sensor Expert Network