Correlated topographic and structural modification on Si surface during multi-shot femtosecond laser exposures: Si nanopolymorphs as potential local structural nanomarkers

Large-Scale Laser Fabrication of Antifouling Silicon-Surface Nanosheet Arrays via Nanoplasmonic Ablative Self-Organization in Liquid CS2 Tracked by a Sulfur Dopant

“…Structural and Chemical Characterization. Moreover, compared to common laser-induced ripples produced on Si surfaces in ambient air or other gases, 12,13,[16][17][18]31,32 the Si NSs fabricated in liquid CS 2 exhibit in their Raman spectra predominantly the only characteristic Si band at ≈520.5 cm −1 (full-width at half-maximum ≈8.1 cm −1 ) with the very minor content of a-Si shown by the weak shoulder band at 470 cm −1 (Figure 2b). The latter band is similar to (negligible broadening and shoulders) that of the initial crystalline wafer (peak at ≈521 cm −1 and full-width at half-maximum ≈7.6 cm −1 ), accounting for the shallow Raman pump penetration at the 488 nm laser wavelength (≈10 nm 33 ), indicating the deep 488 nm laser probing of the NS arrays.…”

“…The stress-induced spectral shift of the main peak accompanied by the weak increase in its halfwidth indicates the predominating hydrostatic (diagonal), rather than the deviatoric (off-diagonal), component of the stress tensor. 32 The residual stresses averaged over the 488 nm laser penetration depth in the modified crystalline layer are of tensile character, and their magnitudes can be evaluated, using calibration coefficients C ≈ 4 or 1.88 cm −1 /GPa, 32 as ≤0.1 GPa, being at the minimum level compared to the stresses, induced during "dry" femtosecond-laser nanopatterning of Si wafer surfaces under similar conditions. 32 Such persistent crystallinity of the nanopatterned Si surface, negligible traces of highpressure Si phases, and related residual stresses 31,32 The preserved Si crystallinity may imply the predominating sedimentation of the doping impurities on the outer wafer surface and nanograin boundaries within the resolidified (potentially amorphous) material, as shown by our top-view XPS analysis, indicating a number of S, O, and C dopant states in the laser-modified surface layer (Figure 3).…”

Surface-Enhanced IR-Absorption Microscopy of Staphylococcus aureus Bacteria on Bactericidal Nanostructured Si Surfaces

“…% (not shown), similarly to Si NPs produced by nanosecond laser ablation of the Si wafer in water ( Figure 1e). All three types of patterns demonstrate a loss of structural order-LO/TO-line shift and broadening, presence of amorphous (a-Si) and high-pressure phases Si-III,XII [24] in Figure 2b, which is more pronounced for the wet patterning, specifically in CS 2 .…”

Fabricating Femtosecond Laser-Induced Periodic Surface Structures with Electrophysical Anisotropy on Amorphous Silicon

“…An additional contribution to the observed effect may as well be caused by anisotropic crystalline and amorphous Si phase distribution within LIPSS, according to [ 9 , 38 ]. In presence of the LIPSS with high amplitude on the surface of a-Si:H film, the charge transport along the LIPSS direction occurs in the highly conductive nc-Si phase which is mainly distributed along the LIPSS ridges [ 38 ]. At the same time, in the orthogonal direction, the charge transport paths are crossed by the ablated valleys of the surface relief, which contain mainly an amorphous phase with significantly lower conductivity than the nc-Si.…”