Internal structure and conductivity of laser-induced graphitized wires inside diamond

Abstract

The paper considers nanostructured interior and conductive characteristics of graphitized wires formed inside single-crystal diamond by laser microstructuring. A series of wires was formed by using different laser pulsewidths (from 150 fs to 10 ns) and varying spatial orientation of the laser beam in the crystal. Electrical resistance of the wires was measured and quasi-longitudinal sections of the wires were studied with scanning electron microscopy. Turning the laser beam inside the diamond crystal results in considerable modification of the mutual arrangement of the laser-induced sp2 nanoplates oriented along the {111} crystallographic diamond planes, however, this has a weak influence on the macroscopic conductivity of the wires. In contrast, increase in the laser pulsewidth in the range studied increases both the wire conductivity and the thickness of the sp2 inclusions. The wires formed by ultrashort (150 fs–5 ps) laser pulses contain numerous quasi-parallel sp2 nanoplates with rare intersections, the actual path of the charge transport along the wires remaining unknown. With increasing pulse width to 10 ns the number of the sp2 nanoplates becomes much smaller, but they form an uninterrupted conductive chain.