An electrode is provided. The electrode includes a contact pad composed of boron-doped polycrystalline diamond (BDD)； a fiber core composed of BDD extending longitudinally from the contact pad from a first end that is in direct contact with the contact pad to an opposing second end； and a polycrystalline diamond (PCD) cladding that coats and hermetically seals the contact pad and the fiber core. A first portion of the contact pad and a second portion at or near the second end of the fiber core are not coated and hermetically scaled by the PCD cladding. A method of fabricating the electrode is also provided.
