| In order to satisfy the life sciences,medicine,microelectronics and optical preface science such as the demand for high quality vacuum window,the preparation of high density,high quality of nanodiamond vacuum window becomes more and more urgent,window film structure compactness and mechanical strength of a direct impact on the performance of vacuum window,and the improvement of secondary nucleation rate can improve the compactness and mechanical strength of nano diamond film layer.In this paper,microwave plasma chemical vapor deposition device?MPCVD?made by ourselves was used to prepare nano-diamond film with CH4/H2/Ar as the gas source.The method of enhancing the secondary nucleation of nano-diamond film and the preparation method of nano-diamond vacuum window enhanced by the secondary nucleation were explored,and the performance of the prepared NCD vacuum window was tested.The specific research content includes the following aspects:?1?Influence of substrate surface pretreatment on nucleation density and subsequent growth of diamond film.Results show that the use(including 0.2 m of diamond fine powder and anhydrous ethanol ultrasonic suspension grinding silicon substrate,with the increase of milling time,nucleation density has increased gradually,when milling time after more than 10 h,nucleation density of 1010cm-1,again increasing milling time,the increase rate of the nucleation density smaller,close to the saturated,then grinding 30 h silicon substrate in the diamond slurry ultrasonic oscillation 30 min,nucleation density reached 10 12 cm-1 order of magnitude.Due to the competitive growth mechanism of grains,as the nucleation density increases,the grain size decreases gradually and the grain boundary increases,and the secondary nucleation increases gradually in the subsequent growth process of diamond film.?2?Influence of H2/Ar flow ratio on the growth of nanodiamond films.The results show that:with the hydrogen flow gradually reduced,argon flow gradually increased,C2group content increased,secondary nucleation enhanced,diamond grain size gradually decreased,non-diamond phase content also gradually increased,film quality became worse.?3?Influence of circulating power regulation on the growth of nano-diamond film.The results show that the increased power can promote the sufficient dissociation of methane gas and produce more C2 dimer.Deposition in the process of using high power promoting the growth of secondary nucleation-normal power-high power to promote the circulation regulation power of the secondary nucleation growth process,can promote nucleation stage in high power led plasma produced in more C2,which results in the plasma IC2/IH?alpha ratio increase,not only enhances the secondary nucleation,the quality of diamond thin films have been improved to a certain extent.?4?Preparation of nano-diamond film vacuum window after secondary nucleation and enhancement.The copper and molybdenum mask method was used to prepare the micron diamond protective frame,and the impurities on the nano-diamond window film were treated by hydrogen plasma and mixed acid etching,and the light transmittance of the vacuum window was improved as a whole.The leakage rate of the nano-diamond vacuum window with a thickness of 17?m was measured with a self-made leakage rate measuring device,and the leakage rate reached 5.6×10-10pa·m3/s. |
PDF Full Text Request