Ultra-high growth rate of boron-doped diamond films with optimized growth parameters using in-liquid microwave plasma CVD

In this work, boron doped diamond (BDD) films were deposited onto a silicon substrate using the in-liquid microwave plasma chemical vapor deposition (IL-MPCVD) method. During the synthesis of BDD films, the effect of solvent, pressure, power and distance between the substrate and the microwave antenna on the growth rate of BDD films was studied. Pressure varied from 20 to 80 kPa at the interval of 20 kPa, power from 500 to 600 W at the interval of 50 W and distance from 1 to 1.5 mm. These different conditions resulted in the formation of both nanocrystalline and microcrystalline BDD films. Synthesized BDD films were characterized by Raman spectroscopy, laser microscopy, and optical emission spectroscopy. The highest growth rate of 410 μm/h is obtained as compared to the previous literature. Good synthesis parameters were used to deposit large area BDD films and the surface area expanded from 7 to 35 mm2. Along with this, the electrochemical properties of BDD films were studied in two different electrolytes. Concerning the growth rate, larger redox potential difference, IL-MPCVD is an effective method than the conventional microwave plasma chemical vapor deposition (MPCVD) method for the fabrication of high growth BDD films. In this research, we synthesized BDD films with a B/C ratio of 1000 ppm by adjusting pressure, microwave power, and the substrate-to-electrode distance to determine the optimal synthesis conditions. This enabled us to determine the optimal synthesis conditions while examining variables like boron concentration and growth rate. By employing these optimized synthesis conditions, we successfully expanded the surface area of the BDD film from 7 to 35 mm2, which represents a fivefold increase. Most importantly, this is the first time reported the highest growth rate of 410 μm/h is achieved using this technique with to obtain highly crystalline BDD films. Additionally, we conducted an investigation into the electrochemical properties of BDD films in various electrolytes.