A 13C diamond is doped by proton induced transmutation. P-type doping is achieved by the 13C(p,αγ)10B reaction. N-type doping is achieved by the 13C(p,γ)14N reaction. The transmutation reaction that occurs is determined by selection of proton beam energy. Stacks of junctions each calculated to be in the order of 10 nm thick have been achieved.