Study On Growth Of Diamond Films By MPCVD In Hydrogen-depleting Atmosphere

Due to its excellent physical and chemical properties,diamond films have attracted widespread attention from scholars.In recent years,many studies have found that diamond films can also be produced under hydrogen-depleted atmospheres using CO₂/CH₄ or Ar/CO₂/CH₄ systems.In particular,diamond films prepared using CO₂/CH₄and CO₂/CH₄/N₂ systems are more advantageous to The grain size can effectively improve the electrochemical performance of the film.Therefore,it is of great significance to study the growth law of diamond films in CO₂/CH₄ and CO₂/CH₄/N₂systems.In view of the deposition characteristics under hydrogen-poor environment,this article specifically studied the structure,quality,and electrochemical performance of diamond film in the CO₂/CH₄ and CO₂/CH₄/N₂ systems under the influence of process conditions,in order to prepare a good conductivity.The high mechanical strength nano-diamond films provide theoretical and experimental basis for the preparation of nano-diamond electrode materials.This paper studied the effect of CO₂/CH₄ and CO₂/CH₄/N₂ on the morphology and quality of nanodiamond films on a 2kW microwave plasma deposition device produced by Woosinent Co.,Ltd.,and obtained the microstructure of acicular nanodiamonds.The influence laws between the relevant electrochemical properties,the experimental results obtained are as follows:1.In the CO₂/CH₄ system,when the CO₂%is between 10%and 50%,the grain size increases first and then decreases with increasing CO₂ content.When CO₂/CH₄=10%,the needle Nanodiamond particles can reach 13nm in diameter.The surface morphology of the film changes from pin-like to spherical nanoparticles.The acicular particles in the film are mainly composed of a diamond phase and a graphite phase.The graphite phase contributes to the electrical conductivity and is located outside the diamond phase.When CO₂/CH₄=10%,the volt-ampere cycle curve of the film is approximately rectangular,and has a large potential window.The oxidation-reduction reaction on the surface of the film is reversible,showing good conductivity,voltage-voltage characteristics and capacitance.When CO₂/CH₄ is>40%,the film does not substantially exhibit electrochemical activity.Therefore,films prepared with CO₂/CH₄=10%are more suitable as electrode materials.2.In the CO₂/CH₄/N₂ system,when the N₂ flow rate is in the range of 30-70 sccm,the nitrogen plasma has little effect on the surface morphology of the film.The surface of the film is a fine weed.The grain size shows a trend of decreasing first and then increasing.When the N₂ flow rate is 50 sccm,the diameter of the needle-like nano-diamond particles is about 7.6 nm.As the N₂ flow rate increases,the agglomerate surface morphology changes from pin-like to spherical nanoparticles.When the nitrogen concentration is 30 sccm,50 sccm,and 70 sccm,respectively,the volt-ampere cycle curve is asymmetric and deviates from the rectangular feature,so its conductivity and voltammetry characteristics are weakened compared to the CO₂/CH₄ system,and the redox reaction at the thin film electrode is irreversible.of.3.In the CO₂/CH₄/N₂ system,when the flow rate of N₂ is in the range of 84-88 sccm,the film surface is uneven,there are obvious grooves and pores,the shape of the particles is irregular,and the agglomeration phenomenon is obvious.With the increase of the nitrogen flow rate,the agglomerates decrease,the grain size decreases significantly,and the crystal grains begin to change into grains.When N₂=95 sccm,the crystal grains show a distinct needle structure.When N₂=86sccm and N₂=88sccm,the voltatric cycle curves of the films all exhibit an approximate rectangular shape,and the redox peaks are small and have a large potential window.When N₂=86 sccm,the film has a higher specific surface area,and the film exhibits a better conductive property,which shows a greater advantage in the application of the electrode material.