Diamond-like Carbon Patterning by the Submerged Discharge Plasma Technique via Soft Solution Processing

Submerged plasma-assisted discharge direct patterning of diamond-like carbon (DLC) onto the silicon substrate in ambient conditions has succeeded as a new and novel soft solution process. In this environmentally benign technique, a copious amount of pure ethanol (ca. 4 mL) was locally activated with a maximum of ca. 0.23 mkWh by an as-electrochemically synthesized ultrasharp tungsten tip. With the assisted submerged plasma, the decomposed ethanol molecules are anodically patterned directly onto the silicon substrate in ambient conditions. The physical nature of DLC patterns was accessed by profilometry, atomic force microscopy, scanning electron microscopy, and transmission electron microscopy analysis. Furthermore, Fourier-transform infrared, Raman, and X-ray photoelectron spectra were analyzed for chemical compositions and structures, such as surface functionalization, carbon-carbon bonding, and sp²-sp³ ratio, respectively. From a Berkovich-configured nanoindentation analysis, Young's modulus and hardness have shown increasing trend with increasing sp³-sp² ratio in DLC patterns of 68.5 and 2.8 GPa, respectively. From the electrochemical cyclovoltammetry analysis, a maximum areal specific capacitance of 205.5 μF/cm² has been achieved at a scan rate of 5 mV/s. The one-step, green, and environmentally sustainable approach of rapid formation of DLC patterns is thus a promising technique for various carbon-based electrode fabrication processes.