Electro-Deposition of Carbon Structures at Mid Voltage and Room Temperature Using Ethanol/Aqueous Solutions

Abstract

Direct syntheses of carbon structures including nanodiamond, microdiamond and diamond-like carbon (DLC) on silicon wafers by liquid phase electro-deposition are presented. The solution (ethanol/water) was employed as electrolyte at different concentration levels. Assays were carried out maintaining constant the electric potential between the silicon electrodes in the range of (80−300 V) at current density of approximately 2.0 mA/cm 2 . Scanning electron microscopy showed that non-uniform, smooth and heterogeneous structures were produced. The structural composition was evaluated by micro-Raman spectroscopy. A mechanism for the formation of sp 3 and sp 2 hybridizations is proposed.Diamond and carbon related materials have been considered promising materials for many industrial applications due to their superb physicochemical properties such as high hardness, low friction coefficient, wear resistance, high thermal conductivity, chemical inertness, and good biocompatibility, among others. 1-4 Diamond and carbon related materials have been produced by a variety of chemical vapor deposition techniques (CVD), 1, 2 as well as the low temperature deposition process, such as the electro-deposition. 3,4 The first attempt to grow carbon films by electro-deposition technique was reported by Namba 5 and ever since that, others groups have used such technique for carbon films preparation. 3-14 Sreejith et al. obtained diamond-like carbon (DLC) at low voltages (80-300 V) and 1 mm interelectrode separation, which gives electric fields of 0.08-0.3 Vm −1 . 11 Graphite and silicon were employed as electrodes (anode/cathode) and ethanol as electrolyte. It is still not clear whether the carbon film deposited had as its source the electrolyte, or the graphite electrode itself or both.In this work we report the results of our investigation on electrodeposition of carbon films containing nanodiamond and diamond inclusions, diamond-like carbon (DLC) and graphitic phases on silicon wafers, which were submerged in an aqueous ethanol solution. All assays were run at room temperature, without heating or cooling and with a low energy consumption. Raman spectra and scanning electron microscopy images are presented and discussed, and a mechanism for the formation of the sp 3 and sp 2 hybridization/bonding is proposed. ExperimentalMirror polished pieces of n-type silicon (100) with resistivity of about 1 .cm and dimensions of 30 × 10 × 0.3 mm 3 were used as electrodes (anode and cathode). Prior to deposition process, the silicon substrates were cleaned by ultrasonic treatment in acetone for 30 min. The electrolyte was a solution constituted of analytical grade Merck R ethanol and deionized water. The solution was not agitated during the deposition process. The distance between the electrodes was fixed at 25 mm, the same value for all experiments. The voltage applied between the electrodes was maintained constant during each experiment and ranged from 80 V to 300 V. Heating or cooling was never applied, so the temperature of the system had a slig...

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