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Abstract

Micrometer width and nanometer thick wires with different shapes were produced $\approx $ $3~\mu $ m below the surface of a diamond crystal using a microbeam of He+ ions with 1.8 MeV energy. Initial samples are amorphous and after annealing at $T\approx 1475$ K, the wires crystallized into graphite-like structures, according to confocal Raman spectroscopy measurements. The electrical resistivity at room temperature is only one order of magnitude larger than the in-plane resistivity of highly oriented pyrolytic bulk graphite and shows a small resistivity ratio ($\rho \left(2~\text{K}\right)/\rho \left(315~\text{K}\right)\approx 1.275$ ). A small negative magnetoresistance below T  =  200 K was measured and can be well understood taking spin-dependent scattering processes into account. The used method provides the means to design and produce millimeter to micrometer sized conducting circuits with arbitrary shape embedded in a diamond matrix.