Radiation Effects And Damage Mechanisms Of CNT-FET

Carbon Nanotubes（CNTs）have excellent electrical properties due to their unique one-dimensional electrical transport.With their ultra-small size and excellent electrical properties,carbon nanotubes（CNTs）are one of the most promising candidates for next-generation channel materials in cutting-edge transistors,while CNTs are also extremely radiation-resistant.The electronic components in space satellites are exposed to radiation from the galactic universe.However,the radiation damage mechanism of CNT-FETs is under-researched,poor device uniformity,lack of radiation response to low-energy protons and uncertainty about the effect of surface adsorption during radiation have not been solved.In this paper,CNT-FET back-gate devices and CNT-FET top-gate devices were designed and fabricated based on CNT network thin film materials,and the displacement damage degradation mechanism and the total dose damage degradation mechanism of CNT-FET back-gate devices were investigated using proton and electron irradiation experiments,respectively.In addition,the electrical response of CNT-FET top-gate devices under compound stress fields was also investigated.The main research contents and results are as follows:Firstly,a deep study was conducted on the proton radiation resistance of CNT-FET back-gate devices using low energy protons with an energy of 150 ke V.The threshold voltage(V_th),on-state current(I_on)and effective hysteresis window width（H）of the device change very little when the proton fluence is accumulated to 5×10¹³ p/cm²,indicating that the CNT material and the CNT-FET back-gate device have a strong radiation resistance to low-energy proton.However,increasing the fluence to 5×10¹⁴ p/cm²,the number of defects and interface states introduced by both the fixed charge of the oxide layer and displacement damage introduced by the total dose effect start to increase strikingly,resulting in significant degradation of the device performance.Secondly,the resistance of CNT-FET back-gate devices to total dose radiation was investigated in depth using electrons with an energy of 3 Me V.The improvements in device performance found after electron irradiation were not only observed in the consistency of the device electrical properties,but also in the optimisation of parameters such as on-state current,mobility,subthreshold swing and channel resistance to varying degrees.These improvements in device performance were associated with the decomposition of-OHs on the CNT surface,the introduction of defects in the carbon nanotubes and improved contacts at the carbon nanotube junctions.Finally,the worst-case bias conditions during irradiation of CNT-FET top-gate devices were investigated at room temperature,followed by X-ray radiation at 80°C under the worst-case bias condition to investigate the synergistic effect of temperature,voltage and radiation stress in the complex stress field.This is caused by the re-release of the oxide layer captured charge introduced by irradiation at high temperatures under thermal stress.