Recent advances in the manufacture of synthetic diamond are creating new opportunities for diamond as a material for advanced technology. Laser writing with femtosecond pulses enables 3D fabrication of a variety of components inside diamond for a range of applications. Focusing at high numerical aperture inside the diamond, with adaptive optics used for aberration correction, non-linear absorption leads to a perturbation of the diamond structure on a scale less than a micrometre, without any damage to the surrounding material or surface. Working in different fabrication regimes, it is possible to generate in the same system electrically conductive wires, optical waveguides and coherent colour centres. In this talk, we present our new results on structural characterisation of the laser modifications within diamond. These include the extraction of a cross-section from a laser written wire using a focused ion beam, which is subsequently thinned and analysed by transmission electron microscopy (TEM). This reveals the internal structure of the laser written features, crucially showing that there is no bulk conversion of the diamond and sp2 bonded carbon is only formed within small 100-nm scale clusters. The sp2 clusters are accompanied by micro-cracks in the principal diamond cleavage plane which mediate the generated stress.
|