Study On Preparation Of Nanostructured Nitrogen-doped Nanocrystalline Diamond And Its Electron Emission Performance In S-band Microwave Field

With the rapid development of vacuum microelectronics, high-power microwave, terahertz technology, the present thermionic cathode and photocathode do not satisfy the requirements for electron beam sources in radio-frequency(RF) guns. Therefore, developing a new cold cathode material with excellent electron beam emission characteristics and quality is the focus in current researches. In this dissertation, the nitrogen-doped nanodiamond(N-NCD) films as cold cathode were investigated, which were synthesized through microwave plasma enhanced chemical vapor deposition technology. For the preparation of nanostructured N-NCD films, a nickel nano-film was firstly deposited on the surface of N-NCD films through the magnetron sputtering process. T he nickel-coated N-NCD film was annealed to form in-situ nickel nanodots worked as hard mask in reactive O2/Ar plasma etching. The effects of nickel n ano-film deposition process, annealing technology and O2/Ar plasma etching process on nanostructured N-NCD films were carefully characterized by scanning electron microscopy(SEM), Raman spectroscopy, atomic force microscopy(AFM) and other testing methods. Finally, the influence of surface nanostructuring on the emission characteristics of the N-NCD cathode was also analyzed and compared through the observation of S-Band radio-frequency microwave pulse electric field.The results show that:(1) the density and the distribution of in-situ formed nickel nanodots are depended on the thermal annealing time and the thickness of the nickel nano-film. That is to say, the in-situ nickel nanodots with highest density and best distribution uniformity were prepared from the 6 nm thin nickel nano-film after exceeding 20 minu tes annealing process.(2) The addition of Ar gas in the plasma source is benefit to nanostructure N-NCD films during the plasma etching. If the content of Ar in reactive gas source is about 45%, the obtained nanostructured N-NCD films have porous surface structure with uniform distribution and large roughness.(3) Surface nanostructuring treatment can improve the S-band microwave emission current density of N-NCD cathodes. At the microwave gradient field of 72.1 MV/m, the emission current density of N-NCD cathode increases to be about 41% after the Ar/O2 plasma etching treatment.