Diamond synthesis by electrolysis of acetates

A new method of electrochemical synthesis of different forms of carbon, inc luding nanocrystalline diamond, is described. The electrolyte consists of a solution of ammonium acetate in acetic acid. The electrolysis is carried o ut by applying a shifted-square alternating voltage in the 10-100 Hz freque ncy range. The peak-to-peak voltage amplitude is 60 V and voltage shift is 10 V. The working temperature is 70-75 degreesC. In this work, electrodes a re monscrystalline boron-doped silicon plates. The morphology and crystalli ne structure of the deposit have been examined by scanning (SEM) and transm ission electron microscopy (TEM), and Raman spectroscopy. Both TEM and Rama n measurements have confirmed unambiguously the formation of diamond nanocr ystals in the deposit. As several studies have underlined the role of CH3. and H-. radicals for CVD diamond growth, the basic idea of the present work was to look for the electrochemical production of these radicals. This was achieved by anodic oxiddation of acetate ions (CH; production) and cathodi c reduction of ammonium ions (H-. production). Using non-symmetric alternat ing polarisation conditions, both anodic and cathodic species are alternati vely generated and coexist at the electrode surface during a short period o f time. Thus, it is believed that, in some areas of the substrate, conditio ns arise that are quite similar to those that take place in CVD methods of diamond growth. (C) 2001 Elsevier Science B.V. All rights reserved.