Bright field top-view optical micrographs of a (100) InP surface processed with a single laser pulse in air ( and ) at different peak fluences of (a), 0.74 (b), 0.91 (c), and (d).
Area of the ablation crater formed in the single-pulse irradiated (100) InP surface as a function of the incident peak fluence of of the laser pulse (, , in air). The line represents a least-squares fit of the experimental data to a model based on a spatially Gaussian shaped laser beam.
Scanning force microscopic topography images of a (100) InP surface processed with single laser pulses in air ( and ) at different peak fluences of (a), 0.74 (b), 0.91 (c), and (d). The images are encoded in a common linear gray scale with darker values representing lower lying surface levels. The horizontal lines indicate the location of the cross sections shown in Fig. 4.
Cross-sectional crater profiles through the SFM topography images of the single femtosecond-laser-pulse ablated InP surfaces shown in Fig. 3 (see the horizontal dotted white lines). Note that the scale in horizontal direction (position) is 320 times larger than in vertical direction (depth). The shaded region indicated in (c) has been subjected to additional TEM investigations.
Fluence dependence of the ablation crater depth formed in a (100) InP surface upon single femtosecond-laser pulse irradiation ( and ); open squares: center depth; full circles: data obtained by the cross-sectional analysis based on Fig. 4(c).
Bright field cross-sectional TEM image of the region indicated by the shaded region in Fig. 4(c). (a) SAEDPs were recorded in two different image locations as indicated by two circles. (b) and (c) show the corresponding images SAEDP 1 and SAEDP 2. The gray arrow marks the direction of the femtosecond-laser beam (normally incident to the sample).
Dark field cross-sectional TEM images of the region indicated by the shaded region in Fig. 4(c). (a) The small black arrows indicate some specific nanometer-sized grains formed in the resolidified layer. Additional insets show two different image locations inside (c) and outside (b) the central protrusion. The gray arrow marks the direction of the femtosecond-laser beam (normally incident to the sample).
Surface reflectivity of a (100) InP surface imaged at 400 nm wavelength: 400 fs (a) and 8 ns (b) after the exposure to a femtosecond laser in the ablative regime (, , , and 54° angle of incidence). The image in (c) shows the permanent surface modification in the same surface region as acquired after several seconds. All three images are taken from Ref. 5.
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