7 Micro-hole Arrays and Net-like Structure Fabrication …
235
Fig. 7.24 Experimental setup for microsized structure-assisted nanostructure fabrication
The observed micro-patterning is explained with Fresnel’s diffraction theory. In addition, two types of spatial frequency surface structures were found, namely laserinduced periodic surface structure (LIPSS) and laser-induced periodic curve surface
structure (LIPCSS). LIPCSS appears at the bottom of the ZnSe surface. Unlike
LIPSS, LIPCSS is independent of laser polarization. The formation of LIPCSS was
because of the interference between the reflected laser field on the valley surface and
the incident laser pulse. The microsized structure assisted nanostructure formation
opens up the possibility for fabricating the nanosized structure on the wafer surface
with ultrashort laser pulses.
The entire diffraction experimental setup is shown in Fig. 7.24. All irradiations
were performed in air environment under normal incidence. The experiment is
conducted on a commercial Ti:sapphire regenerative amplifier laser system (Legend
Elite, Coherent). It generates laser pulses at a center wavelength of 800 nm with
pulse duration of 60 fs and pulse energy of 2.0 mJ. The laser system operates at a
repetition rate of 1 kHz. The laser beam goes through a lens with a focal length of
150 mm and irradiates on the sample surfaces. The sample is placed at a distance,
typically a few hundreds of micrometers behind a hexagonal transmission electron
microscope (TEM) mask (the dimension of the TEM mask is 3 mm, and the dimension of a hexagon is 60 μm), which is illuminated at a distance of Z ≈ 120 mm
through the focal lens. The diameter of the laser spot on the sample surface is about
1 mm. The diameter of laser spot is measured and determined with 1/e
2 intensity
level. An electronic shutter is used to control the irradiation pulse numbers, and a
neutral density filter, a λ/2 plate, and a polarizer are used to change the laser power
continuously. The samples are mounted on an XYZ-translation stage controlled by
235
Fig. 7.24 Experimental setup for microsized structure-assisted nanostructure fabrication
The observed micro-patterning is explained with Fresnel’s diffraction theory. In addition, two types of spatial frequency surface structures were found, namely laserinduced periodic surface structure (LIPSS) and laser-induced periodic curve surface
structure (LIPCSS). LIPCSS appears at the bottom of the ZnSe surface. Unlike
LIPSS, LIPCSS is independent of laser polarization. The formation of LIPCSS was
because of the interference between the reflected laser field on the valley surface and
the incident laser pulse. The microsized structure assisted nanostructure formation
opens up the possibility for fabricating the nanosized structure on the wafer surface
with ultrashort laser pulses.
The entire diffraction experimental setup is shown in Fig. 7.24. All irradiations
were performed in air environment under normal incidence. The experiment is
conducted on a commercial Ti:sapphire regenerative amplifier laser system (Legend
Elite, Coherent). It generates laser pulses at a center wavelength of 800 nm with
pulse duration of 60 fs and pulse energy of 2.0 mJ. The laser system operates at a
repetition rate of 1 kHz. The laser beam goes through a lens with a focal length of
150 mm and irradiates on the sample surfaces. The sample is placed at a distance,
typically a few hundreds of micrometers behind a hexagonal transmission electron
microscope (TEM) mask (the dimension of the TEM mask is 3 mm, and the dimension of a hexagon is 60 μm), which is illuminated at a distance of Z ≈ 120 mm
through the focal lens. The diameter of the laser spot on the sample surface is about
1 mm. The diameter of laser spot is measured and determined with 1/e
2 intensity
level. An electronic shutter is used to control the irradiation pulse numbers, and a
neutral density filter, a λ/2 plate, and a polarizer are used to change the laser power
continuously. The samples are mounted on an XYZ-translation stage controlled by