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Artificial diamond is created by exposing graphite to pressures on the orderof 10\,GPa and temperatures of about 2000\,K. Here, we provide evidence thatthe pressure exerted by the tip of an atomic force microscope onto grapheneover the carbon buffer layer of silicon carbide can lead to a temporarytransition of graphite to diamond on the atomic scale. We perform atomic forcemicroscopy with CO terminated tips and copper oxide (CuOx) tips to imagegraphene and to induce the structural transition. For a local transition, DFTpredicts that a repulsive barrier of $\approx13$\,nN, followed by a forcereduction by $\approx4$\,nN is overcome when inducing the graphite-diamondtransition. Experimental evidence for this transition is provided by theobservation of third harmonics in the cantilever oscillation for relativeflexible CO terminated tips and a kink in the force versus distance curve forrigid CuOx tips. The experimental observation of the third harmonic with amagnitude of about 200\,fm fits to a force with an amplitude of $\pm 3$\,nN.The large repulsive overall force of $\approx 10$\,nN is only compatible withthe experiment if one assumes that the repulsive force acting on the tip wheninducing the transition is compensated by an increased van-der-Waals attractionof the tip due to form fitting of tip and sample by local indentation. Thetransition changes flat sp$^2$ bonds to corrugated sp$^3$ bonds, resulting in adifferent height of the two basis atoms in the elementary cell of graphene.Both tip types show a strong asysmmetry between the two basis atoms of thelattice when using large repulsive tip forces that induce the transition.Experimental data of tunneling current, frequency shift and dissipation areconsistent with the proposed transition. The experiment also shows that atomicforce microscopy allows to perform high pressure physics on the atomic scale.

Evidence for temporary and local transition of sp2 graphite-type to sp3 diamond-type bonding induced by the tip of an atomic force microscope