scholarly journals Effect of Crystallographic Orientation on Structural Response of Silicon to Femtosecond Laser Irradiation

2021 ◽  
Author(s):  
Xin Zhang ◽  
Liang Zhang ◽  
Sergey Mironov ◽  
Rongshi Xiao ◽  
Liang Guo ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Crystallographic Orientation ◽  
Electron Backscatter Diffraction ◽  
Structural Response ◽  
Target Material ◽  
Target Surface ◽  
Femtosecond Laser Irradiation ◽  
Nanosecond Laser ◽  
Transmission Electron ◽  
Thermal Melting

Abstract Femtosecond laser has been widely utilized for modification of crystal structure to achieve desired functions. So far, however, the effect of crystallographic orientation on the induced structure by femtosecond laser processing has yet been comprehensively studied. The present work is undertaken in an attempt to fill this gap in our knowledge. To this end, commercial-purity Si is used as a target material and high-resolution transmission electron microscopy as well as electron backscatter diffraction are applied to examine the irradiation-induced microstructural changes. The structural response of the pulsed material is found to be principally influenced by the crystallographic orientation of the target surface. Specifically, at the surface orientation close to {111}, a pronounced amorphization effect is observed whereas no disordered material is detected at the orientations close to {100}. This phenomenon could be explained by the lowest crystallization speed required by the (111) surface due to its smallest surface energy. Compared with nanosecond laser, non-thermal melting induced by femtosecond laser induces mild thermal gradient and favors recrystallization.

scholarly journals Effect of crystallographic orientation on structural response of silicon to femtosecond laser irradiation

2021 ◽  
Vol 127 (3) ◽  
Author(s):  
Xin Zhang ◽  
Liang Zhang ◽  
Sergey Mironov ◽  
Rongshi Xiao ◽  
Liang Guo ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Irradiation ◽  
Crystallographic Orientation ◽  
Structural Response ◽  
Femtosecond Laser Irradiation

scholarly journals Synthesis of Nanotips Through Femtosecond Laser Ablation of Glass with Assisted Gas

2021 ◽  
Author(s):  
Nikunj Patel
Keyword(s):  
Femtosecond Laser ◽  
Building Materials ◽  
High Vacuum ◽  
Synthesis Method ◽  
Femtosecond Laser Ablation ◽  
Target Surface ◽  
Laser Pulses ◽  
Single Step ◽  
Femtosecond Laser Irradiation ◽  
Ambient Conditions

Nanotips are the key nanostructures for many applications. Until now, the nanotips of only the crystalline materials have been produced via various deposition methods which require sophisticated equipment, high vacuum, and clean room operations. This thesis proposes a single step, rapid synthesis method using femtosecond laser irradiation at megahertz frequency with background flow of nitrogen gas at ambient conditions. Amorphous nanotips are obtained without the use of catalyst. The nanotips grow from highly energetic plasma generated when target is irradiated with laser pulses. The vapor condensates, nanoparticles and droplets from the plasma get deposited back on to the hot target surface where they experience force imbalance due to which the stems for the nanotips growth are initiated. Once the stems are generated, the continuous deposition of vapor condensates [sic] provides building materials to the stems to complete the growth of nanotips. Further study found that the growth of the nanotips is influenced by laser parameters and gas conditions.

Femtosecond Laser Ablation of Titanium and Silicon

2000 ◽  
Author(s):  
Mengqi Ye ◽  
Costas P. Grigoropoulos
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Laser Fluence ◽  
Laser System ◽  
Femtosecond Laser Ablation ◽  
Laser Pulses ◽  
Femtosecond Laser Irradiation ◽  
Nanosecond Laser ◽  
Iccd Camera ◽  
Plume Emission

Abstract Femtosecond laser ablation of titanium and silicon samples has been studied via time-of-flight (TOF), emission spectroscopy and microscopy measurement. Laser pulses of around 100 fs (FWHM) at λ = 800 nm were delivered by a Ti:sapphire femtosecond laser system. A vacuum chamber with a base pressure of 10−7 torr was built for ion TOF measurement. These ion TOF spectra were utilized to determine the velocity distribution of the ejected ions. While nanosecond laser ablation typically generates ions of a few tens of eV, femtosecond laser irradiation even at moderate energy densities can produce energetic ions with energies of up to a few keV. The most probable energy of these fast ions is proportional to the laser fluence. The structure and number of peaks of the TOF spectra varies with the laser fluence. Images of plume emission were captured by an intensified CCD (ICCD) camera. The plume emission spectrum was analyzed by a spectrometer. Laser ablated craters were measured by an interferometric microscope and a scanning electron microscope (SEM). Ablation yield was expressed as a function of laser fluence, and number of shots.

Laser-Target Interactions and its Effect on Surface Morphology of Laser Deposited thin films

1990 ◽  
Vol 201 ◽  
Author(s):  
R. K. Singh ◽  
D. Bhattacharya ◽  
J. Narayan
Keyword(s):  
Energy Density ◽  
Particle Density ◽  
Target Material ◽  
Target Surface ◽  
Solid Material ◽  
Laser Evaporation ◽  
Nanosecond Laser ◽  
Laser Target ◽  
Surface Evaporation ◽  
Surface Temperatures

AbstractThe laser-target interactions during pulsed laser evaporation (PLE) of materials have been investigated in detail. Sub-surface temperatures have been calculated to be higher than the surface temperatures during planar surface evaporation of the target material. While the evaporating surface is being cooled due to the latent heat of vaporization, sub-surface superheating occurs due to the finite absorption depth of the laser beam. Detailed computer simulations have been carried out to understand the evaporation characteristics of different targets (Si, YBa2Cu3O7 ) as a function of laser and target variables. For silicon targets irradiated with 25 nanosecond laser pulses (energy density of 10J/cm2, absorption coefficient of 105 cm−1), the sub-surface temperatures were found to be more than 2000°C above the surface evaporation temperatures. The sub-surface superheating increased with increasing energy density and absorption depth. This internal superheating effects may lead to volume evaporation of the target where a solid material in form of particles may be ejected from the target surface. Based on the above understanding, parameters required to reduce the particle density in PLE films are predicted.

High-temperature oxidation of CoGa: Influence of the crystallographic orientation on the oxidation rate

2002 ◽  
Vol 17 (10) ◽  
pp. 2489-2498 ◽  
Author(s):  
U. Koops ◽  
D. Hesse ◽  
M. Martin
Keyword(s):  
High Temperature ◽  
Crystallographic Orientation ◽  
High Temperature Oxidation ◽  
Elevated Temperatures ◽  
Electron Backscatter Diffraction ◽  
Ex Situ ◽  
Temperature Oxidation ◽  
Transmission Electron ◽  
Backscatter Diffraction

The crystallographic orientation plays an important role in high-temperature oxidation of the intermetallic compound CoGa. When CoGa is exposed to air at elevated temperatures, the oxide β–Ga2O3 is formed, and different scale growth rates are observed, depending on the crystallographic orientation of the CoGa grains. This dependence is a consequence of the anisotropy of the gallium diffusion rate through the β–Ga2O3 scale and of a topotaxial orientation relationship occurring between β–Ga2O3 and CoGa. The combination of ex situ techniques, such as transmission electron microscopy and electron backscatter diffraction with optical microscopy, applied in situ resulted in a thorough understanding of these relations and of the oxidation process in general.

scholarly journals Theoretical and experimental investigations on the photothermal effect of gold nanorods irradiated by femtosecond and nanosecond laser

2021 ◽  
pp. 327-327
Author(s):  
Dong Li ◽  
Penghui Zhao ◽  
Jing Feng ◽  
Linzhuang Xing ◽  
Bin Chen ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Irradiation ◽  
Gold Nanorods ◽  
Thermal Conversion ◽  
Femtosecond Laser Irradiation ◽  
Photothermal Effect ◽  
Experimental Investigations ◽  
Nanosecond Laser ◽  
Laser Induced Breakdown ◽  
The Impact

Nanoparticle-mediated laser-induced breakdown (LIB) can be used for Nanoparticle synthesis, cell nanosurgery and laser-induced breakdown spectroscopy (LIBS). To investigate the photo-thermal conversion of gold nanoparticles during pulsed laser irradiation, the electron-phonon two-temperature model was established in this study. The impact of laser energy density and pulse width on the thermal conversion and morphology change of gold nanorods were investigated and compared with experimental observations. The results show that the melting threshold of gold nanorods under nanosecond laser irradiation is about twenty times that of femtosecond laser irradiation. The mechanisms of nanorod fragmentation are different between fem to and nanosecond laser irradiation: particle melting is more likely to occur in nanosecond laser irradiation, while the Coulomb explosion is highly likely to occur in femtosecond laser irradiation.

Fabrication of gold nanoparticles in intense optical field by femtosecond laser irradiation of aqueous solution

2008 ◽  
Vol 23 (4) ◽  
pp. 968-974 ◽  
Author(s):  
Takahiro Nakamura ◽  
Yuzuru Mochidzuki ◽  
Shunichi Sato
Keyword(s):  
Aqueous Solution ◽  
Gold Nanoparticles ◽  
Femtosecond Laser ◽  
Size Distribution ◽  
Laser Irradiation ◽  
Optical Field ◽  
Femtosecond Laser Irradiation ◽  
Gold Particles ◽  
Transmission Electron ◽  
The Mean

Gold particles were fabricated by the high-intensity femtosecond laser irradiation of gold (III) chloride trihydrate (HAuCl4) aqueous solution. The structure and size distribution of the prepared particles were evaluated by transmission electron microscopy. The configuration of the gold particles varied with the concentration of the HAuCl4 aqueous solution. The mean particle size and size distribution were changed by the addition of polyvinylpyrrolidone (PVP), which acted as a dispersant, and monodispersed gold nanoparticles with a diameter of about 3 nm were successfully fabricated. The formation process of the nanoparticles is discussed in terms of the optical decomposition of molecules in the highly intense optical field generated by femtosecond laser irradiation.

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