Deposition Of Amorphous Diamond Films By Liquid Electrochemical Deposition

Amorphous diamond films were deposited on(100)silicon substrates at atmospheric pressure and low temperature(50-60℃)with a direct current pulsed power supply using methanol/additive solution as electrolyte.The morphology of the films was analyzed by scanning electron microscopy(SEM)and atomic force microscopy(AFM).The microstructure of the films was analyzed by Raman spectroscopy,transmission electron microscopy(TEM)and transmission electron diffraction(TED).The wear behavior and the degree of hardness of the films were examined on the CERT test system and Nano Indentor.The electrolyte was methanol/deionized water solution with various ratios.The applied potential,the distance between the anode and the substrate and the deposition time were fixed at 1600 V,9 mm and 2 h,respectively.Adding active additive in pure methanol resulted in a remarkable increase in the current density and then in the growth rate of the films up to 0.5μm/h.All the films deposited appear brown or black in color,and do not dissolve in organic solvent such as ethanol and acetone.The SEM observations showed that the continuous and compact films consisted of fine and compact ball-like grains.The more deionized water the electrolyte contains,the bigger the grains are.Raman spectroscopy analysis confirmed diamond structure by the presence of strong peaks at 1330 cm^-1and graphite structure by the presence of peaks at 1596 cm^-1.The strongest peak at 1332 cm^-1 confirmed the highest ratio of diamond phase using methanol/deionized water solution in the ratio of 1:5 as the electrolyte.The certain kind and ratio of active additive could play an important role not only in increasing relative content of diamond phase in the films,but also improving adhesive strength between the films and substrates.C₆H₁₈OSi₂ as the second kind of additive was added in the forenamed methanol/deionized water solution and all the other experimental parameters were the same as before.The resistivity of the solution was slightly increased after adding a small amount of C₆H₁₈OSi₂ into the fixed methanol/deionized water solution,so the current density decreased a little.Continuous and compact films consisted of fine and compact ball-like grains with about 100 nm in diameter were deposited within 2 hours.All the films deposited appear grey or black in color,and do not dissolve in organic solvent such as ethanol and acetone.Raman spectroscopy analysis confirmed diamond structure by the presence of strong peaks at 1330 cm^-1and graphite structure by the presence of peaks at 1596 cm^-1.The analysis of Raman confirmed that adding C₆H₁₈OSi₂ into methanol/deionized water solution in the ratio of 1:5 results in the most diamond phase because of the strongest intensity of the peak at 1331 cm^-1 and the narrowest FWHM(full wave at half maximum).And the analyzed results of electron diffraction pattern confirmed the Diamond 8H and Graphite 2H structure in the films.