| Cathode is the key component of electron source. As the extensive application of the electron source in various fields, the electron source has become more important. Accordingly, the requirement of the cathode is increasingly high. People need the high emission current density and good quality electron beam source to obtain electron beam in high brightness. People have used many methods to make the cathode, in recent years, the film-cathode method that coated with the films of other materials on the substrate has gradually become the focus of the cathode around the world. The film-cathode method can utilize the physical and structural characteristics of the substrate, and can utilize physical and chemical properties of the film materials. So, it is an effective method in improving the performance of the cathode.Film-cathode is the method that the films of other materials are coated on the surface of the cathode to further reduce work function of the cathode. Therefore, the choice of the materials is important, the dissertation mainly consider some important factors of materials, for example, the work function, the conductivity, the density, the thermal stability, and the chemical stability. As the excellent quality materials of cathode emission, lanthanum hexaboride(LaB6)has many advantages, for example, high melting point, the resistance of ion bombardment, anti-oxidation, the high thermal conductivity, the high electrical conductivity, and the excellent chemical and physical stability. So, LaB6 has become the ideal film material in preparation of the film-cathode.In the dissertation, the LaB6 films is deposited on rhenium and silicon spindt arrays by electrophoresis and electron beam evaporation. The electrophoretic deposition techniques, electron beam evaporation processes and silicon spindt arrays preparation processes are researched respectively. The dissertation gets more scientific process parameters. The samples of multi-crystal LaB6 films coated on different substrate using various processes are successfully prepared. Through the analysis of the films surface morphology and structure by SEM and XRD, the result shows that the films that deposited on the Re substrate by electrophoretic deposition is more smooth and the crystallization of the films is very good after annealing, and the films deposited by electron beam evaporation deposition is very dense, and the crystallinity increases gradually with the increasing of the substrate temperature, and the films appear the preferred growth in interplanar <100>.The thermal emission characteristics and stability of film-cathode coated on Re substrate with LaB6 films by electrophoretic deposition are tested in detail. The result shows that film-cathode can gain high current density, it is as high as 0.44 A/cm2 in film-cathode temperature of 1200℃under the vacuum of 2×10-4Pa, and the emission life reaches to 40 hours. Thermal emission stability test shows that vacuum can certainly affect the thermal electron emission properties of LaB6 films, and the emission current gradually reduces with the increase of the vacuum, and the fluctuations of the current also increases. According to the straight-line method of Richardson, the dissertation gains that work function of LaB6 is 2.56eV.I-V characteristics and stability of field emission of silicon array and LaB6 film-arrays have also been studied. The results show that silicon array coated by LaB6 films has good and stable emission characteristics. In vacuum of 8×10-5Pa and voltage of 1650 V, the total field emission current from the LaB6 film-arrays reached to 125μA, which is 125 times than pure silicon spindt arrays. The test shows the current density is 3.1mA/cm2. LaB6 film-arrays have a good field emission stability, in the testing period of 30 minutes, the current is between 18μA and 24μA, and eventually the current is stabilized at 20μA. The results show that LaB6 films cold cathode have high emission current and high stability, it is the kind of ideal field emission arrays. |
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