Temperature-dependent electrical and structural characterization of laser-induced graphitic microwires in CVD diamond

An array of 2500 vertical graphitic microwires was fabricated within a single-crystal diamond plate with the purpose of creating distributed electrically conductive structures intended for the development of electronic devices operating at high temperatures. To this end, the structural, morphological, and electrical properties of the diamond/graphite system were investigated as a function of temperature up to 550 °C, by means of optical and secondary electron microscopy (SEM), micro-Raman spectroscopy and current-voltage measurements. The vertical microstructuring of the diamond bulk was obtained by a laser-induced phase transition from diamond to graphite by means of ultra-short laser pulses (100 fs duration, 800 nm wavelength, 1 kHz repetition rate). As inferred from SEM micrographs, the graphitic wires display a high-aspect-ratio with length of approximately 200 μm and diameter of about 10 μm. The electrical resistivity of the single microwire is estimated to be 0.49 ± 0.15 Ω cm at room temperature, then decreasing linearly with temperature with a coefficient of approximately −1 × 10−2 K−1. Raman spectroscopy results point out the absence of structural alterations after high-temperature operations.