Fabrication Of The SiC Nanowires And Their Piezoresistance Properties

The sensor is an extension of the human five senses.It is an important tool for humans to obtain information.It is also called electric five features and it is widely used in various fields of human life and social development.With the development of society and the continuous exploration of applications,the fabrication of high-performance pressure sensors that can be used under harsh conditions such as high temperature and radiation has become more and more urgent.SiC materials are one of the representative materials for building high-performance pressure sensors for tough operating conditions due to their wide bandgap,high thermal conductivity,high breakdown voltage,and electron mobility.Due to the dual advantages of low-dimensional nanostructures and silicon carbide,low-dimensional silicon carbide nanomaterials have confirmed that they have a larger piezoresistive effect than the corresponding bulk materials.In this work,the development of high performance SiC pressure sensors is targeted.The SiC nanowires with similar size and controllable doping elements were fabricated through typical pyrolysis of polysilazane on the carbon cloth substrate.Atomic force microscopy?AFM?was used to detect the piezoresistive properties of SiC nanowires with different doping types.The effects of single doping elements and two-element co-doping on the piezoresistive properties of SiC nanowires were investigated.The mechanism of the piezoresistive effect of SiC nanowires with different doping elements is discussed and analyzed,and technical reference and theoretical support are provided for the development of high-performance pressure sensors suitable for harsh environments.Main tasks as follows:1.The preparation of N-doped 3C-SiC nanowires was achieved by high temperature pyrolysis of organic precursors with polycarbosilane as precursor and cobalt nitrate as catalyst.The entire pyrolysis process was executed within the atmosphere mixture of nitrogen and argon.The nanowires have a diameter of²00 nm and a N element concentration of about 2.32 at.%.The transverse piezoresistance coefficient?_[11?_0]of the obtained N-doped 3C-SiC nanowires increased from 2.65×10^-11 Pa^-1-5.33×10^-11 Pa^-1 as the applied forces increased from 27.26 nN to 111.14 nN.More impressive,the corresponding GF can be increased up to 31.98,which is higher than the GF value of undoped SiC nanowires.2.The preparation of P-doped 3C-SiC nanowires was achieved by high temperature pyrolysis of organic precursors with polycarbosilane as precursor and cobalt nitrate as catalyst.The entire pyrolysis process was executed within the atmosphere of argon.The nanowires have a diameter of about 180 nm and a P element concentration of about 0.1 at.%.The transverse piezoresistance coefficient?_[11?_0]of the obtained P-doped 3C-SiC nanowires increased from-4.77×10^-11 Pa^-1 to-26.99×10^-11 Pa^-1 as the applied forces increased from 27.26 nN to 121.63 nN.More impressive,the corresponding GF can be increased up to-161.9,which is much higher than the GF value of undoped SiC nanowires.It is only lower than the maximum strain factor reported in current SiC nanostructures.3.The preparation of N/P co-doped 3C-SiC nanowires was achieved by polycarbosilane as precursor and cobalt nitrate as catalyst.The entire pyrolysis process was executed within the atmosphere mixture of nitrogen and argon.By changing the ratio of nitrogen-argon mixed gas,it can achieve N/P co-doped 3C-SiC nanowires with two different sizes and different N concentrations.The P element doping concentration were 0.1 at.%and 0.11 at.%,and the N element concentrations were 2.16 at.%and 10.16 at.%,respectively.The piezoresistive performance test results of the two groups of samples are analyzed as follows.As the applied pressure is gradually increased,the maximum transverse piezoresistive coefficient of two groups of samples are-146.30x10^-11 Pa^-1 and-47.15x10^-11 Pa^-1,respectively.The maximum strain coefficients GF are-877.79 and-282.89,respectively,which are larger than the GF values of N-doped or P-doped 3C-SiC nanowires.Among them,the strain coefficient of the first sample N/P co-doped 3C-SiC nanowires is higher than the maximum strain coefficient obtained in the current SiC nanomaterial system.