Using Scanning Electrochemical Microscopy to Determine the Doping Level and the Flatband Potential of Boron‐Doped Diamond Electrodes

Abstract

International audienc

Raman Imaging and Kelvin Probe Microscopy for the Examination of the Heterogeneity of Doping in Polycrystalline Boron-Doped Diamond Electrodes

“…Different electrochemical behavior was recorded for the bright regions (Figure B). The shape of the approach curves depends on the applied potential, a characteristic of semiconductor interfaces . Indeed, at a selected potential of E F = 0.5 V vs Ag/AgCl applied to the diamond interface, the recorded feedback currents showed a lesser amount of positive feedback.…”

“…A negative feedback (the tip current decreases when the tip−substrate distance decreases, as diffusion of IrCl 6 2- to the tip electrode is blocked) is observed if the diamond film is behaving as an insulator, whereas a positive feedback is expected for highly doped diamond electrodes (Figure ). The SECM approach is based on a previous report by us in which polycrystalline diamond electrodes of different doping levels were investigated . The redox couple chosen to determine the doping level of the BDD sample was IrCl 6 2-/3- , an outer-sphere redox couple.…”

“…By decreasing the potential applied to the BDD interface and recording the approach curves, the heterogeneous rate constants at the diamond electrode, k eff , as a function of potential, E F , could be calculated. Fitting of these data using the theory of electron transfer at semiconductor/electrolyte interfaces was not possible, as the areas were still too highly doped . An almost linear relationship between k eff and E F is observed.…”

“…Bard and Swain used scanning electrochemical microscopy (SECM) as well as conductive atomic force microscopy to study hydrogen-terminated boron-doped diamond electrodes with different doping levels . SECM has also been employed in our group to determine the local doping level of boron-doped polycrystalline electrodes . Recently, Macpherson et al used SECM in conjunction with cathodoluminescence and conducting atomic force microscopy (C-AFM) to study the impact of grain-dependent boron uptake on the electrochemical and electrical properties of polished, polycrystalline, and oxidized BDD electrodes .…”

“…9 SECM has also been employed in our group to determine the local doping level of boron-doped polycrystalline electrodes. 35 Recently, Macpherson et al used SECM in conjunction with cathodoluminescence and conducting atomic force microscopy (C-AFM) to study the impact of graindependent boron uptake on the electrochemical and electrical properties of polished, polycrystalline, and oxidized BDD electrodes. 36 Whereas C-AFM showed no evidence for enhanced grain boundary conductivity, different characteristic conductivity domains were observed corresponding to different crystallites in the diamond electrode.…”