The Effect Of Nitrogen Plasma On The Diamond Films

CVD diamond film has great prospects in various applications, due to its excellent physicochemical properties. At home and abroad, significant research on the preparation of diamond film is one of the hot problems. MPCVD technology is acknowledged as the preference method of all synthesis technology to prepare high quality, high purity diamond films. A large amount of researches show that nitrogen addition can change the structure and properties of diamond films during their growth. In this paper, the effect of nitrogen plasma on the diamond films was systematic investigated in R2.0-MPCVD apparatus designed by Woosinent company. The primary work in the research are listed following:1.The influences of the pretreatment and nucleation temperature on the nucleation were discussed. Surface grinding method is the most commonly used pretreatment technique. After this process, uniform and fine scratches were obtained on silicon wafer, which were high-energy nucleation points. The nucleation rate of diamond was improved by creating scratches. And the residues of 0.5μm diamond powder can be used as the seed crystals. At the same time, the nucleation temperature was controlled between 800 to 900℃, which can be conducive to the nucleation of diamond and control the content of graphite phase.2.The effect of low concentration nitrogen on diamond film was systematically researched. The results of SEM, Raman and XRD characterization methods showed that the grain size of diamond films gradually decreased with the increasing of the nitrogen concentration. 2%, the concentration of nitrogen, was advantageous to reveal the(100) orientation. When the concentration of nitrogen was 6%, the growth of diamond and graphite was hindered by nitrogen, and the films were discontiguous.3.The effect of high nitrogen concentration on the diamond films was detailedly investigated. The results showed that the high nitrogen concentration can further fine the diamond grain. However, the relationship between the reducing diamond grain size and the increasing nitrogen content was not linear relation. The diameter of diamond grain displayed a tendency of decreasing firstly and then magnifying while the nitrogen concentration increase continuously. When the concentration of nitrogen was 90%, the film was ultrananocrystalline diamond film, and the grain size was 10 nm.4.The electrical properties of diamond films have also when the nitrogen concentration is high. The experimental results indicated that the impedance of diamond films can be minimized by the increase of nitrogen. But there existed a lowest point, and the impedance will become higher if the nitrogen concentration exceed this point. The lowest impedance can be obtained under the condition of 85% nitrogen.In this research, the effect of both low nitrogen concentration and high nitrogen concentration on the diamond film has be studied. It shows a integrally reducing trend following the augment of nitrogen concentration. Orientation can be distinguished from the SEM image of diamond films that deposited in relative low nitrogen concentration. And it was mainly the mix of(111) orientation and(400) orientation. Structure of diamond grain will alter from graininess to “needle-like” and finally become a shape of “cauliflower” while increase the nitrogen concentration in a relatively high area. Beyond that, the impedance of diamond films can be significantly declined and the nitrogen concentration of the minimum is 85%.