Research On Field Emission Array Cathode Technology Of Single Crystal Hexaboride

In a microwave tube,the most important component is a cathode that emits electrons as an electron source.Compared with traditional hot cathodes,field emission cathodes have the advantages of no heating,high current density,and quick start-up,which is an ideal source of electron emission.Single crystal La B₆ is a material with low work function,stable physical and chemical properties,high melting point and low evaporation rate,and has excellent field emission performance.At present,the preparation of the single crystal LaB₆ field emission array cathode is mainly a method of preparing a silicon nitride mask by PECVD and electrochemical etching after photolithography.However,the preparation process is complicated and the shape of the emitter is difficult to control.Therefore,it is the focus of this study to find a simple preparation method with controlled emitter morphology.In order to achieve the field emission cathode emission requirements,we designed two methods to prepare single-crystal La B₆ field emission array cathodes,namely:micro-fabrication electrochemical etching method,electric spark wire cutting assisted electrochemical corrosion method,and successful adjustment of various process parameters.A single-crystal La B₆ field emission array cathode with excellent electron emission performance was prepared.The main research contents of the thesis include:1.Using OPERA software simulation calculations,the emitter structure has a significant impact on the cathode field emission capabilities,and explore the appropriate field emission cathode structure,to provide a theoretical basis for the follow-up preparation work.2.The amorphous silicon masking layer was deposited on the surface of the substrate by RF magnetron sputtering.The study shows that as the RF power increases,the deposition rate increases first and then decreases,and the deposition rate is inversely proportional to the uniformity of the film.The higher the Ar gas flow rate,the lower the film deposition rate and the linear relationship between the two.3.A tapered single crystal La B₆ field emission array cathode was prepared by micro-electrochemical etching.The effects of exposure time,hardening temperature,etching time,electrolyte concentration and electrolytic current on the corrosion results of the emitters were studied.The best process parameters for the electrochemical etchingprocesswereobtainedasfollows:electrolyteconcentration V?H₃PO₄?:V?C₂H₅OH?:V?H₂O?=1:10:10,electrolysiscurrent10mA,electrolyte temperature 0?,electrolysis time 1h.4.Columnar hexaboride array cathode structure was designed.The single crystal LaB₆ was processed according to the simulation results,and the emitter was sharpened by electrochemical etching.Finally,a columnar LaB₆ field emission array was successfully fabricated cathode.5.Self-designed test fixtures and test equipment were constructed,and the field emission cathodes prepared were tested for performance.After testing,the sharp-tapered structure prepared has an open field of 5.5V/?m,and the current density required for the threshold electric field is not reached in the test range;the opening electric field of the columnar structure is 4.4⁵.8V/?m,and the threshold electric field is 8.3⁹.4V/?m,and good cathode emission stability...