Abstract
Controlling laser-induced periodic surface structures on semiconductor materials is of significant importance for micro/nanophotonics. We here demonstrate a new approach to form the unusual structures on 4H-SiC crystal surface under irradiation of three collinear temporally delayed femtosecond laser beams (800 nm wavelength, 50 fs duration, 1 kHz repetition), with orthogonal linear polarizations. Different types of surface structures, two-dimensional arrays of square islands (670 nm periodicity) and one-dimensional ripple structures (678 nm periodicity) are found to uniformly distribute over the laser-exposed areas, both of which are remarkably featured by the low spatial frequency. By altering the time delay among three laser beams, we can flexibly control the transition between the two surface structures. The experimental results are well explained by a physical model of the thermally correlated actions among three laser-material interaction processes. This investigation provides a simple, flexible, and controllable processing approach for the large-scale assembly of complex functional nanostructures on bulk semiconductor materials.
Highlights
Femtosecond laser-induced periodic surface structures, as universal phenomena that occur on all types of materials including metals, semiconductors, and dielectrics [1–3], have been a topic of intensive study for decades
We investigate the control of 2: (a) two-dimensional (2D) LIPSS formation on a 4H-SiC crystal surface by using the temporally delayed irradiation of triple femtosecond laser beams, associated with the orthogonal linear polarizations in successive sequences
HSF-type ripple generate laser-irradiated over, for the incident laser with different linear polarizations, the spatial orientation of file consists of multiple short-ranged fragments with the semi-periodic inter ripple structures becomes varied, but it is always perpendicular to the laser polarization proximately
Summary
Femtosecond laser-induced periodic surface structures (fs-LIPSSs), as universal phenomena that occur on all types of materials including metals, semiconductors, and dielectrics [1–3], have been a topic of intensive study for decades. Through using double-fs-laser-beam irradiation, two kinds of 1D LIPSSs—high-spatial-frequency (HSF) and low-spatial-frequency (LSF) ripple structures—were demonstrated on silicon surfaces at different time delay regimes [21–24]. In our recent report of a three-fs-laser-beam irradiation experiment, the regularity of 1D ripple structures formed on a 4H-SiC surface was significantly improved, and the structure period was found to transfer from HSF to LSF regime [32], which performs more degrees of freedom and has superiority in controlling the LIPSS formation. We investigate the control of 2D LIPSS formation on a 4H-SiC crystal surface by using the temporally delayed irradiation of triple femtosecond laser beams, associated with the orthogonal linear polarizations in successive sequences. When their mutual time delays are varied in a range of 0~60 ps, we can observe the formation of
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