Precisely Controlled Growth Of Flexible SiC Field Emission Cathode Materials And Their Electron Emission Properties

Field emission, one of the natural characteristics of the low-dimensional nanomaterials, has spread across broad applications prospects in the display and vacuum electron devices. The critical foundations for the applications of these nanomaterials are reduce the turn-on fields and improve the electron emission stabilities. In this thesis, aim to exploration the novel and efficient Si C flexible field emission cathode based on the mechanism of local field enhancement effect and tailore the electron state density near the Fermi level by the atom doping, the flexible Si C single-crystalline low-dimensional cathodes were successfully synthesized via pyrolysis of polymeric precursor process. The morphology and doping levels of Si C low-dimensional nanomaterials with enhanced field emission properties be achieved by optimizing two key experimental parameters of the cooling rate and pyrolysis atmosphere. The obtained Si C flexible field emission cathodes present excellent flexibility, low turn-on fields and high field electron emission stabilities. These innovative achievements have been obtained of this thesis are enumerated blow.(1) The N-doped Si C quasialigned nanowires array flexible cathodes were synthesized on the carbon fiber cloth substrate via the pyrolysis of polymeric precursor(PSN) process. The N2/Ar mixture was incorpored as the shielding gas and dopant during the whole pyrolysis process and the PSN precursor provide the Si and N source. These survey results indicated that the as-synthesized cathode present high flexibility and the turn-on fields were 1.90~2.65 V/μm as the distance of cathode and anode in the range of 400~800 μm.(2) The N-doped Si C quasialigned nanoneedles array flexible cathodes were achieved by controlling the cooling rate during the pyrolysis process. The field emission behaviors indicated that the turn-on fields of flexible cathode could be significantly reduced by growth the Si C emitters into quasialigned nanoneedles array. As compared with conventional Si C nanowires emitters, the turn-on field of nanoneedle emitters reduced from 2.19 V/μm to 1.15 V/μm.(3) The field emission characteristics of N-doped Si C nanoneedles flexible field emission cathode under high temperature were tested. The survey results confirmed that the nanoneedles could competent as effective field emission cathode under the high temperature harsh working conditions. The turn-on fields of flexible cathode decreases with the increase of temperatures, which could be attributed to the reduction of the work function of Si C nanoneedles induced by the raise of temperatures.(4) The Si C nanostructures with ultra-sharp tips and tailored N doping levels were synthesized by adjusting the cooling rates and the components of N2/Ar mixture via the pyrolysis of polymeric precursor process. Field emission properties measurements disclosed that the as-synthesized Si C field emission cathode present excellent electron emission properties and the turn-on field is ranged in 1.38~1.11 V/μm with the N dopant concentration raised from 4.39 to 7.58 at.%. The flexible cathodes display stable turn-on field when subjected to 200 bending cycles, and yet the field electron emission always remained about the same under various bending states. These results suggested that the obtained Si C field emission cathode was mechanically robust with high stabilities.(5) The P-doped single-crystalline Si C nanoparticles flexible field emission cathode was synthesized via the pyrolysis of polymeric precursor process by using the Fe PO4·4H2O power and Ar as the dopants and shielding gas, respectively. Field emission properties measurements disclosed that the exsted P dopants could significantly reduce the turn-on field of nanoparticles. The field electron emission characteristics of Si C cathode under different bending cycles, bending states and temperatures revealed that the P-doped Si C field emission flexible cathode is mechanically robust with high stabilities and could competent as effective components under the high temperature harsh working conditions.