Nanostructured interior of laser-induced wires in diamond

Diamond Detector With Laser-Formed Buried Graphitic Electrodes: Micron-Scale Mapping of Stress and Charge Collection Efficiency

“…[30], a buried columns distance d around 170 µm was preferred to maintain an adequate drift distance of charge carriers at few tens of Volts of applied bias. The rectangular face-centered cell (partially resembling a hexagonal shape [27]) adopted for the device would assure a minimized overlapping of laser-induced stressed regions mainly localized within the {111} planes [19,31], although this appears particularly important for relatively low d distance in micrometer range.…”

“…The laser-induced local transformation of diamond into graphite represents a powerful tool used for the development 3D-contacts devices [9][10][11][12][13], all-carbon detectors [14][15], graphite resistors on diamond [16] (opening the way to redesign position sensitive devices based on distributed resistive superficial contacts [17]), as well as the realization of complex three-dimensional geometries [18]. Several research groups reported detailed investigations on their experimental process conditions [19][20][21], mainly studied to: increase the buried contact aspect-ratio (length over diameter) in order to decrease contacts' distance for the same detector active volume; assure a good buried-contact conductivity by optimizing laser-treatment parameters (power-density, scan velocity, repetition rate) experimenting with either nanosecond, picosecond or femtosecond pulsed laser sources. However, graphitic paths are strongly process-dependent and a proper choice of laser-treatment parameters is fundamental for the realization of high quality contacts in device fabrication.…”

“…However, graphitic paths are strongly process-dependent and a proper choice of laser-treatment parameters is fundamental for the realization of high quality contacts in device fabrication. For example, on a micrometer scale, a buried laser-generated graphitic column is far from an ideal cylinder and its geometry looks like a kind of a tree with thin branches spreading out not only along the laser beam direction, but also fanning out from the central body of the column, with the sp 3 to sp 2 ratio strongly dependent on the laser parameters [19,22]. Lagomarsino et al [22] reported a significant difference in morphology and electrical conductance of the buried graphitic structures fabricated by nanosecond-and femtosecond-pulsed laser radiation, with a more defective layers formed around the ns-columns.…”

“…Salter et al [26] studied the internal structure of fs-laser induced graphitic wires using TEM and electron energy loss spectroscopy and revealed multiple micro-cracks and nanoclusters of sp 2 bonded carbon embedded into sp 3 bonded diamond matrix. Ashikkalieva et al [19] applied scanning spreading resistance microscopy to investigate spatial arrangement of sp 2 bonded nano-sheets forming conductive network inside wires. Forcolin et al [21] used the proton microbeam to map local charge collection efficiency (CCE) with Ion Beam Induced Charge (IBIC) technique for fs-laser induced buried graphitic electrodes array.…”

“…Graphitized superficial strips and pads, obtained applying a similar laser-treatment apparatus with ArF source, were used to define the overall detector contact geometry. Aiming at preserve the good electronic quality of the pristine diamond sample, in comparison to other investigated cell-shapes [9,13,27], the laser-formed buried contacts geometry of the detector was designed to minimize the overlapping between stressed regions originated by the laser-treatment itself, which mainly propagates along the {111} crystal direction [19].…”