Nanostructures on SiC surface created by laser microablation

Silicon carbide (SiC), as it is well-known, is inaccessible to usual methods of technological processing. Consequently, it is important to search for alternative technologies of processing SiC, including laser processing, and to study the accompanying physical processes. The work deals with the investigation of pulsed laser radiation influence on the surface of 6H–SiC crystal. The calculated temperature profile of SiC under laser irradiation is shown. Structural changes in surface and near-surface layers of SiC were studied by atomic force microscopy images, photoluminescence, Raman spectra and field emission current–voltage characteristics of initial and irradiated surfaces. It is shown that the cone-shaped nanostructures with typical dimension of 100–200 nm height and 5–10 nm width at the edge are formed on SiC surface under nitrogen laser exposure (λ = 0.337 μm, tp = 7 ns, Ep = 1.5 mJ). The average values of threshold energy density 〈Wthn〉 at which formation of nanostructures starts on the 0 0 0 1 and imagesurfaces of n-type 6H–SiC(N), nitrogen concentration nN ≅ 2 × 1018 cm−3, are determined to be 3.5 J/cm2 and 3.0 J/cm2, respectively. The field emission appeared only after laser irradiation of the surface at threshold voltage of 1000 V at currents from 0.7 μA to 0.7 mA. The main role of the thermogradient effect in the processes of mass transfer in prior to ablation stages of nanostructure formation under UV laser irradiation (LI) was determined. We ascertained that the residual tensile stresses appear on SiC surface as a result of laser microablation. The nanostructures obtained could be applied in the field of sensor and emitting extreme electronic devices.