Fabrication And Field Emission Performance Of Low-dimensional Carbon-based Vacuum Electronic Devices

Field emission has gained widespread attention because it is a unique way called cold cathode emission,which has been applied to flat panel display,electron microscope electron beam source,X-ray source and so on.The key to improving field emission performance lies in the selection and modification of field emission cathode materials.One-dimensional materials are considered to be the most valuable and meaningful cathode materials for research.Initially,this paper studies the field emission performance based on silicon carbide and its composite materials,and then expands to the field emission performance study of two-dimensional novel layered titanium carbide,which can be described in detail:（1）Fabrication and field emission study of Si C/MWCNT.Field emission cathode was fabricated by screen printing,and the surface of the cathode was treated by tape processing.Because the tape is so sticky that it can take away a large number of field emission points,the tape was pretreated,and the effects of different tape types and pretreatment times were studied.In addition,the optimal times were used for subsequent sample processing.Due to the poor adhesion between silicon carbide and the substrate,the composite carbon nanotube material was combined to study the effect of different composite ratios on the field emission performance.（2）Fabrication and field emission study of Si C/conductive polymers.The polyaniline（PANI）and polypyrrole（PPY）coatings are coated on one-dimensional silicon carbide nanowires（1D Si C NWs）by cyclic voltammetry method,which is simple,feasible and can control the thickness of the coatings.Compared with the original Si C,the average turn-on field(E_on)of Si C decorated with PANI and PPY decreased.The minimum E_on of Si C/PPY even dropped significantly to 0.95 V/?m,which shows that by depositing PANI and PPY,the field emission performance has improved due to the increase in electrical conductivity.However,as the deposition thickness continues to increase,the conductivity will reach saturation,and an overly thick coating will block the effective field emission points and reduce the effective field emission point current density of the cathode,resulting in poor field emission performance.Therefore,this paper studies the synergy of the conductivity effect and the thickness effect,finds the optimal thickness,and proves that Si C/PPY has potential in the field of vacuum field emission electronic devices.（3）Fabrication and field emission study of Ti₃C₂T_x.Although Ti₃C₂T_x has been extensively studied in applications as Li ion or Na ion electrical storage devices,there are few reports on Ti₃C₂T_x in the field of field emission.In this paper,two-dimensional Ti₃C₂T_x MXene was fabricated by etching away the Al layer in Ti₃Al C₂ with hydrofluoric acid（HF）at room temperature,and was used as the cathode of a field emission device for the first time.The device has good field emission performance,with a low E_on of 2.7 V/?m and good stability,which is much lower than 1D rival Ti C nanowires（7.1 V/?m）and some other 2D materials,such as Mo S₂ and graphene.Our research shows that due to the enlarged layer spacing after etching,its unique accordion structure has uniformly distributed sharp edges,which not only serves as an additional field emission point but the larger layer spacing also reduces the field shielding effect.Numerical simulation results show that the E_local at the sharp edge is indeed higher than that of other places.It means that the sharper edges are exposed due to the increased interlayer spacing,which can greatly improve the field emission performance.The edge effect we found is also consistent with other previous reports.Therefore,the two-dimensional layered Ti₃C₂T_xcan be applied to the field of vacuum electronic equipment other than energy storage and conversion equipment.