Laser surface micropatterning (texturing) of hard materials and coatings is an effective technique to improve tribological systems. In the paper, we have investigated the laser-induced surface modifications and micropatterning of diamond-like nanocomposite (DLN) films (a-C:H,Si:O) using IR and visible femtosecond (fs) lasers, focusing on the improvement of frictional properties of laser-patterned films on the micro and macroscale. The IR and visible fs-lasers, operating at λ = 1030 nm and λ = 515 nm wavelengths (pulse duration 320 fs and pulse repetition rate 101 kHz), are used to fabricate different patterns for subsequent friction tests. The IR fs-laser is applied to produce hill-like micropatterns under conditions of surface graphitization and incipient ablation, and the visible fs-laser is used for making microgroove patterns in DLN films under ablation conditions. Regimes of irradiation with low-energy IR laser pulses are chosen to produce graphitized micropatterns. For these regimes, results of numerical calculations of the temperature and graphitized layer growth are presented to show good correlation with surface relief modifications, and the features of fs-laser graphitization are discussed based on Raman spectroscopy analysis. Using lateral force microscopy, the role of surface modifications (graphitization, nanostructuring) in the improved microfriction properties is investigated. New data of the influence of capillary forces on friction forces, which strongly changes the microscale friction behaviour, are presented for a wide range of loads (from nN to μN) applied to Si tips. In macroscopic ball-on-disk tests, a pair-dependent friction behaviour of laser-patterned films is observed. The first experimental data of the improved friction properties of laser-micropatterned DLN films under boundary lubricated sliding conditions are presented. The obtained results show the DLN films as an interesting coating material suitable for laser patterning applications in tribology.

We report on the enhancement of nitrogen-vacancy (NV) luminescence induced by the bulk structure modification of a type IIa single-crystal diamond with a visible picosecond laser. Using online monitoring of picosecond-laser-induced photoluminescence (PL) in the bulk regions we found that the integrated intensity of the NV PL is significantly increased after the bulk microstructure formation. The confocal PL spectroscopy investigations of the bulk microstructures have evidenced the enhanced NV luminescence and the splitting of the ${\mathrm{NV}}^{-}$ emission. The increased concentration of the NV defects during picosecond-laser bulk modification correlates with the formation of ${\mathrm{sp}}^3$ carbon allotropic structures and other defect centers revealed in PL/Raman spectra of high-stress regions near the fabricated microstructures.