Piezoresistance Properties Of Low-dimensional SiC Nanomaterials

Sensor technology is “features” of human understand and transform the world and is one of the key technologies in the modernization process.Due to the advantages of high sensitivity,good stability,low energy consumption,and ease of intergration,piezoresistive pressure sensors are widely used in aerospace,petrochemical,medical,automobile etc.In the numerous sensors,the semiconductor pressure sensor has attracted much attention due to its excellent performance.As the ?-N semiconductor,Silicon Carbide?SiC?has apparent advantage in serving under harsh work conditions?e.g.,high temperature,high powers and high frequencies?,owing its wide-band-gap structure,high thermal conductivity,high electron mobility,high breakdown voltage and excellent mechanical properties.Around the research and development of the SiC pressure sensor,the existed research works major focused on the bulk materials of thin film,polycrystal and single crystal.Low-dimensional nanomaterials,respected to nano effect and perfect crystal structure,present incomparable high sensitivity piezoresistance effects compared to their conventional bulk counterparts,and provide an opportunity for the development of the new type efficient pressure sensor.In this thesis,directed by the exploitation of high sensitive SiC perssure sensor,SiC one-dimensional nanomaterials with different doping elements and morphology were synthesized via the pyrolysis of polymeric precursor.Subsequently,the piezoresistance effects in SiC one-dimensional nanomaterials were systematic examined by the conduction mode of atomic force microscopy?C-AFM?.These innovative achievements of this thesis are enumerated below:?1?The single crystal B-doped 3C-SiC nanowires were synthesized via the pyrolysis of polymeric precursors of polysilazane?PSN?by using the B₂O₃ powder and Co?NO₃?₂ as the doping source and catalyst,respectively.The whole pyrolysis process was carried out under Ar atmosphere.The negative piezoresistance behaviors were detected on the [???] crystal orientation of the as-synthesized nanowires,and the piezoresistance coefficient of the nanowires falls in the range of-8.83 to-103.42×10-11 Pa-1 at the applied loading forces ranging from 51.7 to 181.0 nN.The calculated gauge factor could be up to-620.5,which is enhanced by more than 8 times compared to the highest ever reported.?2?The single crystal B-doped 3C-SiC nanobelts were synthesized via the pyrolysis of PSN polymeric precursors without introducing catalyst.The B₂O₃ powder was used as the doping source.The whole pyrolysis process was carried out under Ar atmosphere.The negative piezoresistance behaviors were detected on the ??? crystal orientation of the as-synthesized nanobelts.The piezoresistance coefficient of the nanobelts falls in the range of-29.96 to-303.90×10-11 Pa-1 at the applied loading forces ranging from 104.3 to 223.6 nN.The calculated gauge factor could be up to-1823.4,which is enhanced about 3 times compared to the B-doped 3C-SiC nanowires.?3?The single crystal N-doped 3C-SiC nanowires were synthesized via the pyrolysis of PSN polymeric precursors,by using the Co?NO₃?2 as the catalyst.The whole pyrolysis process was carried out under N₂/Ar mixture atmosphere?N₂ were also used as the doping source?.The piezoresistance coefficient of the nanowires is about 4.31×10-11 Pa-1 when the applied loading force is 28.2 nN,the gauge factor is 25.9.In addition,the piezoresistance coefficient of the nanowires increased to 11.77×10-11 Pa-1 by optimization selecting the 405 nm,62.4 mW UV as the excitation source,the calculated gauge factor could be up to 70.6,which is enhanced about 3 times compared to the dark state.