A device comprising a single crystal diamond substrate with a buried electrically conducting layer with μm square openings spaced apart milled into the diamond by ablating the carbon above wherein the step of ablating uses a diode pumped tripled Nd:YAG laser at 355 nm and wherein the square openings have electrical contacts and wherein the resistance measured between the square openings is dominated by the buried electrically conducting layer and on the order of about 1 kΩ.