Structure And Wettability Of Polycrystalline Diamond Films By Thermal Oxidation Treatment

As an important third-generation semiconductor material,diamond can be widely used in semiconductor devices such as optics,microelectronics and nuclear energy,as well as in aerospace,national defense and other fields,and plays an important role that cannot be replaced by other materials.Chemical vapor deposition?CVD?diamond film is currently the most widely used diamond material.The polycrystalline diamond film with silicon wafer,molybdenum wafer,single crystal or polycrystalline material as the growth substrate has a large number of grain boundaries and non-diamond phases,and has a high grain boundary and defect density,which affects the application of high-quality diamond in electricity,heat,optics and other aspects to a certain extent.Removal of non-diamond phases and defects at the grain boundaries,tiny grains,etc in the polycrystalline diamond film to obtain a polycrystalline diamond film with a better crystal shape and a larger grain size,improve the crystal quality of the polycrystalline diamond film,and realize the development of diamond good application in various fields has important research value.In addition,the surface energy,surface wettability and other parameters of diamond are closely related to the surface structure and terminal of diamond film?hydrogen and oxygen?,which are the factors to be considered in the application of diamond-based devices in multiple fields.The study of surface structure,high temperature oxidation treatment and growth of polycrystalline diamond film,as well as its wettability regulation are important research contents in the field of diamond.In this paper,the microwave plasma chemical vapor deposition?MPCVD?method is used to prepare polycrystalline diamond films.The grown polycrystalline diamond films are subjected to high-temperature oxidation treatment and secondary growth to obtain continuous large-grain diamond films and improve the quality of polycrystalline films.And studied the surface wettability and surface energy of the polycrystalline diamond film at various stages.The specific research content and results are as follows:1.The polycrystalline diamond film was grown by MPCVD method with molybdenum wafer as substrate and grown under the atmosphere of H₂:CH₄:N₂=200:5:1,in which N₂ gas was used to obtain?100?texture self-supporting diamond film.The polycrystalline films were characterized by SEM,Raman spectrum and XRD.From the SEM figure,it can be observed that the growth surface is dominated by?100?oriented diamond grains with a square tip,and a large number of nano-diamond particals of non-diamond phases appear between?100?grains.2.The polycrystalline diamond film was oxidized in air at 800?for 15 min.From the SEM topography,we can see that the?100?diamond grains in the growth surface remain,forming?100?oriented diamond single crystal columns with V-shaped growth characteristics.It indicated that?100?diamond had high thermal stability and was not easily oxidized.The nano-diamond particals and non-diamond material between its crystal columns were selectively oxidized and removed,resulting in voids.Using the high-temperature oxidation-treated sample as a substrate,secondary growth was performed by MPCVD.The surface of?100?diamond grains grown,showing a better?100?crystal shape,and the separated crystal columns was reconnected on the upper surface.3.Experimental studies on the wettability and surface energy of polycrystalline diamond films at various stages have shown that different surface structures?grain size,roughness,voids?and modifications?hydrogen and oxygen terminals?had a significant effect on the wettability of polycrystalline diamond films,and its wettability was closely related to the polarity of the droplets.By measuring the contact angle and calculating the dispersion force and polar force,we estimated the roughness and surface energy of polycrystalline diamond films with different surface structures and modifications.The experimental results proved that the surface energy and wettability of the diamond film could be effectively adjusted by controlling the surface structure and modification of the polycrystalline diamond film,and affect the performance of the diamond-based electronic device in the atmospheric environment.In this paper,a method for the preparation of oxidation treatment and secondary growth of high-quality CVD polycrystalline diamond film was proposed.The characteristics of the surface morphology and properties at different growth stages were discussed.The wettability and surface energy of the sample surface were studied.It could improve the growth quality of polycrystalline diamond film,modulate the surface wettability and surface energy of diamond film,and provide valuable data for the research and development of diamond-based devices.