AFM images of the surface morphology of (001) InP after femtosecond-laser irradiation with (a) 1 pulse and (b) 20 pulses with , (), and . Cross-sectional TEM images of (c) a single-pulse crater, (d) LSFL, and (e) HSFL. The lines 1, 2, and 3 indicate the approximate sites (on different craters) for the cross-section samples (c), (d), and (e), respectively. The TEM images were taken along the LIPSS direction (i.e., perpendicular to the LIPSS -vector), which is around 10° from the (100) axis.
Energy-filtered TEM images of a single-pulse crater taken near (a) the edge (rim) and (b) the center. Convergent beam electron diffraction images taken near the center of the crater on (c) the substrate and (d) the resolidified surface layer.
Lateral profiles of the ablated depth (filled circles), and the resolidified layer depth (open circles), measured from the original surface of the substrate. The fit of Eq. (1) is also included as a solid line.
(a) Optical image of a crater after femtosecond-laser irradiation with a single-pulse at and . (b) The square of the diameters for both the resolidified and the ablated region as a function of the laser fluence. The inset of (b) is an optical image of a crater following irradiation with a single pulse of (, as indicated by the arrow). Both optical images have a width of . The fluence used for the TEM experiment is indicated by a vertical dotted line in (b).
Energy-filtered TEM images of (a) LSFL and (b) HSFL.
(a) ADF-STEM image of LSFL and (b) EDS line scan taken from bottom to top across the line in (a). (c) ADF-STEM image of HSFL and (d) EDS line scan taken across the line in (c). Arrows on the ADF images indicate phosphorous-deficient regions observed in the EDS line scans.
(a) and (b) Bright-field STEM images of LSFL showing extended defects.
Efficacy factor as a function of the normalized wave vector , parallel to the laser electric field vector, under -polarized laser at incidence angles , 2°, and 10°. The complex refractive index is and the surface roughness is described by and . An arrow indicates the position of the HSFL feature . The plots are shown offset from each other in the vertical direction for clarity.
ratio of LSFL and HSFL compared with the refractive index of partially amorphized materials for three compound semiconductors at laser wavelength of 800, 1300, and 2100 nm. LIPSS data were taken from Ref. 8; and the were taken from Ref. 45. Symbols: (-) no high-frequency structure observed; (/) no experiment attempted.
Article metrics loading...
Full text loading...