Electrochemical sensitivity of undoped CVD diamond films as function of their crystalline quality

Abstract

The amorphous, sp2-hybridized carbon admixture can play an important role in governing electrochemical properties of diamond layers. From the viewpoint of electrochemistry, heavily boron-doped CVD diamond layers at the level of 1020 atom/cm3 are mainly used. However such a heavy doping can lead to a significant deterioration of the crystalline structure. In the present paper, it has been shown that the electrochemical sensitivity of the undoped diamond electrode is sufficient that overcomes the problem of diamond doping. In this case, we believe that the sp2 amorphous carbon phase admixture can be responsible for electrochemical activity. In order to prove the above hypothesis a series of six electrodes have been fabricated based on the hot filament CVD method of diamond synthesis. Variations in the layer growth conditions lead to its different crystallinity and the content of the amorphous carbon phase. The structural parameters of the obtained electrodes were examined using the Raman spectroscopy, while the electrochemical response of diamond electrode was studied using cyclic voltammetry measurements in 0.1 M KCl and the impedance spectroscopy as well. It has been revealed that in the aspect of chemical and biological applications the obtained materials used as sensing probe possess relatively good electrochemical sensitivity and a wide potential window.