| MEMS mechanical sensors are used in various applications,including aerospace,satellites,military,and nuclear systems,owing to their small volume,lightweight,fast response time,low power consumption,easy miniaturization and integration,and low cost.As the core component of MEMS mechanical sensor,when the force sensing units work in the aerospace and space communication fields with severe radiation,which may cause structural,electrical,and thermal damage to the force sensing units,resulting in a change in their parameters or even their total failure.It is essential to enhance the reliability of the force-sensing units to ensure their efficient,accurate,and effective operation in space and an environment with high radiation levels.Therefore,this paper aims to investigate the radiation hardening characteristics of piezoresistive force-sensing units,high electron mobility transistors（HEMT）force sensing units,and flexible base force sensing units.The radiation hardening ability of micro/nano force sensing units is improved by designing different radiation hardening structures,and the radiation hardening reinforcement of force sensing units is realized through the design of radiation hardening structures.The main work includes the following aspects:1.To address the potential track structure damage caused by irradiation of the force sensing unit,a multi-channel nanostructure is proposed.The use of multi-channel nanostructures facilitates changing the path of potential tracks,inhibiting penetration damage,improving carrier transport by providing multi-channel conduction,and enhancing the resistance to radiation damage.This paper uses a multichannel nanostructure embedded into a conventional silicon piezoresistive force sensing unit,and the sample is irradiated with high fluence.According to the morphology analysis and comparison,the potential track of the typical silicon piezoresistive force sensing unit has a through defect with a size of approximately 10 nm.In the typical silicon piezoresistive force sensing unit,the potential tracks formed by the multi-channel nanostructure do not form a through-damage,and the damage size is reduced to 8 nanometers after irradiated with fluence of5?101 2ion/cm2.By comparing the changes in force sensitivity before and after irradiation,it was found that the sensitivity coefficient of the multi-channel nanostructure embedded in the typical silicon piezoresistive force sensing unit is reduced by 19.6%,the silicon piezoresistive force sensing unit is reduced by 59.4%in the fluences range of1?101 0ion/cm2-1?1012ion/cm2,and the silicon piezoresistive force sensing unit had lost its force-sensitivity properties when the irradiation fluence reaches to5?101 2ion/cm2.By utilizing multi-channel nanostructures as electron tunneling devices,the sensitivity of the force sensing unit embedded in multi-channel nanostructures is increased by 4 times.It has been demonstrated that multi-channel nanostructures can effectively solve the structural damage caused by irradiation and improve the radiation hardening characteristics of typical force sensing units.2.An electron tunneling nanostructure is proposed to mitigate the effects of irradiation on force-sensing units.With electron tunneling nanostructures,electrons are restricted from moving in three-dimension directions,thus reducing the influence of radiation-induced defects on electron movement and enhancing the ability to resist radiation damage.In this paper,electron tunneling nanostructures are embedded within the HEMT force-sensing unit and the samples were irradiated with high fluence.Testing and comparing electrical characteristics revealed that the the leakage current of HEMT force sensing unit is reduced by68.2%,while the leakage current of HEMT force sensing unit embedded in electron tunneling nanostructure is only reduced by 13%after irradiated with fluence of1?101 1ion/cm2.Furthermore,the comparison of the changes in force sensitivity before and after,it was found that the sensitivity of the HEMT force sensing unit embedded in the electron tunneling nanostructure decreases by 5.6%,the HEMT force sensing unit is reduced by 12.2%in the fluences range of1?101 0ion/cm2-1?1011ion/cm2.And the HEMT force sensing unit had lost its force-sensitivity properties when the irradiation fluence reaches to5?101 1ion/cm2.In addition,the embedded force sensing unit of electron tunneling nanostructures is doubled in sensitivity due to the electron tunneling effect of electron tunneling nanostructures.This study has demonstrated that electron tunneling nanostructures can effectively eliminate the problem of electrical damage caused by irradiation,as well as improve the radiation hardening capabilities of conventional force sensors.3.A nanoparticle sponge composite structure is proposed that addresses the issue of thermal damage caused by irradiation of the force-sensing unit.Nanoparticles can be used to reduce the performance changes caused by the thermal expansion of the material structure by taking advantage of the excellent reflection ability of the rays.Generally speaking,the smaller the particle size,the higher the specific surface area,which can form more irradiation loss interfaces and improve the ability to resist irradiation damage.An embedded nanoparticle sponge composite structure is shown in this paper embedded into a typical flexible force-sensing unit.In comparison to the changes in force sensitivity and repeatability before and after irradiation,it is show that in the dose range of 5KGy-100KGy,the sensitivity coefficients of sponge composite structures embedded in flexible force sensing units decreased by 60.9%,the repeatability decreased by 11.4%,and the sensitivity coefficients of sponge composite structures embedded with 50nm WO3 nanoparticle sponge composite structures did not change.The composite materials were optimized to further enhance the sensitivity.A composite structure of nanoparticle fibers with different particle sizes combined with carbon nanotube powder in a 3vol%concentration was prepared and embedded into the flexible force sensing unit to improve the sensitivity coefficient by 3 times and to ensure good resistance to radiation thermal damage.It has been demonstrated that nanoparticle sponges with composite structures can effectively overcome the problem of thermal damage caused by irradiation as well as improve the radiation hardening properties of conventional force sensors. |
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