Formation of diamond nanoparticle thin films by electrophoretic deposition

Thin films of diamond nanoparticles were prepared by electrophoretic deposition (EPD) using 0.5 wt% dispersions in water, ethanol, and 2-propanol. The film growth rate increased with increasing voltage applied to the electrodes. However, an excessive increase in voltage caused the degradation of film morphology. The optimum voltage was 4V with an electrode separation of 5 mm. The film growth rate was higher in organic solvents than in water. The deposited film had a smooth surface with an average surface roughness comparable to the size of primary particles of the source material. It is notable that the EPD films had a considerably higher physical stability than spin-coated and cast films. The stability was further improved by thermally annealing the films. IR analysis revealed that the diamond nanoparticles have carboxy and amino groups on their surfaces. It is considered that the stability of the EPD films originate from a chemical reaction between these functional groups. (C) 2016 The Japan Society of Applied Physics