Nomarski optical micrograph (a) and detailed magnification by SEM (b) of a (111) silicon wafer surface irradiated by five femtosecond-laser pulses ( and ) in air. The horizontal arrows marked with E in (a) indicate the direction of polarization of the femtosecond-laser beam.
Geometry of the laser beam incidence to a rough surface, which has been used to model the formation of LIPSSs.
2D gray scale maps of the efficacy factor for single-crystalline silicon as a function of the normalized LIPSS wave vector for different excitation levels of the material [all for normal incident radiation at ; the polarization E is indicated in (h)]. (a) ; , ; (b) ; , ; (c) ; , ; (d) ; , ; (e) ; , ; (f) ; , ; (g) ; , ; and (h) ; , ; . The values of are encoded in a common linear gray scale with dark colors representing larger values. The symbols A and B label some characteristic features.
LSFL period obtained from the B-feature position in the -map (peak value and upper and lower limits as obtained from a 90% criterion) and maximum value of the efficacy factor for the LSFL feature as a function of the excitation level of the laser-excited silicon. Note the logarithmic carrier density scale.
Nomarski optical micrograph (a) of a (111) silicon wafer surface irradiated by a single femtosecond-laser pulse ( and ) in air. In (b) the 2D-FT of (a) is shown indicating LIPSSs with periods between 680 and 795 nm. The dashed-boxed region in (a) marks the region shown in Fig. 6. The horizontal arrows marked with E in (a) indicate the direction of polarization of the femtosecond-laser beam.
Detailed magnification of the optical micrograph shown in Fig. 5(a).
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