Fabrication route for the production of coplanar, diamond insulated, boron doped diamond macro- and microelectrodes of any geometry.

Highly doped, boron doped diamond (BDD) is an electrode material with great potential, but the fabrication of suitable electrodes in a variety of different geometries both at the macro- and microscale, with an insulating material that does not compromise the material properties of the BDD, presents technical challenges. In this Technical Note, a novel solution to this problem is presented, resulting in the fabrication of coplanar macro- and microscale BDD electrodes, insulated by insulating diamond, at the single and multiple, individually addressable level. Using a laser micromachining approach, the required electrode(s) geometry is machined into an insulating diamond substrate, followed by overgrowth of high quality polycrystalline BDD (pBDD) and polishing to reveal approximately nanometer roughness, coplanar all-diamond structures. Electrical contacting is possible using both top and bottom contacts, where the latter are defined using the laser to produce non-diamond-carbon (NDC) in the vicinity of the back side of the BDD. We present the fabrication of individually addressable ring, band, and disk electrodes with minimum, reproducible controlled dimensions of 50 μm (limited only by the laser system employed). The pBDD grown into the insulating diamond recesses is shown to be free from NDC and possesses excellent electrochemical properties, in terms of extended solvent windows, electrochemical reversibility, and capacitance.