Publications in Scientific Journals:

S. Bashir, M. Rafique, C. Nathala, A. Ajami, W. Husinsky:
"Femtosecond laser fluence based nanostructuring of W and Mo in ethanol";
Physica B: Condensed Matter, 513 (2017), 48 - 57.

English abstract:
The effect of femtosecond laser fluence on nanostructuring of Tungsten (W) and Molybdenum (Mo) has been
investigated after ablation in ethanol environment. A Ti: Sapphire laser (800 nm, 30 fs) at fluences ranging from
0.6 to 5.7 J cm−2 was employed to ablate targets. The growth of structures on the surface of irradiated targets is
investigated by Field Emission Scanning Electron Microscope (FESEM) analysis. The SEM was performed for
both central as well as the peripheral ablated regions. It is observed that both the development and shape of
nanoscale features is dependent upon deposited energies to the target surface as well as nature of material.
Nanostructures grown on Mo are more distinct and well defined as compared to W. At central ablated areas of
W, unorganized Laser Induced Periodic Surface Structures (LIPSS) are grown at low fluences, whereas,
nonuniform melting along with cracking is observed at higher fluences. In case of Mo, well-defined and
organized LIPSS are observed for low fluences. With increasing fluence, LIPSS become unorganized and broken
with an appearance of cracks and are completely vanished with the formation of nanoscale cavities and conical
structures. In case of peripheral ablated areas broken and bifurcated LIPSS are grown for all fluences for both
materials. The, ablated diameter, ablation depth, ablation rate and the dependence of periodicity of LIPSS on
the laser fluence are also estimated for both W and Mo. Parametric instabilities of laser-induced plasma along
with generation and scattering of surface plasmons is considered as a possible cause for the formation of LIPSS.
For ethanol assisted ablation, the role of bubble cavitation, precipitation, confinement and the convective flow is
considered to be responsible for inducing increased hydrodynamic instabilities at the liquid-solid interface.

Femtosecond laser Tungsten Molybdenum Laser fluence Surface modification Laser induced periodic surface structures

Created from the Publication Database of the Vienna University of Technology.