Femtosecond laser heat affected zones profiled in Co∕Si multilayer thin films

Abstract

In this letter, we describe an approach for assessing collateral thermal damage resulting from high intensity, femtosecond laser irradiation. Polycrystalline Co thin films deposited on Si (100) substrates and buried under an amorphous Si film were prepared for plan-view transmission electron microscopy (TEM) prior to laser irradiation by femtosecond laser pulses. A heat affected zone (HAZ) resulting from single pulse irradiation at a fluence of 0.9J∕cm2 was determined by TEM imaging and point-wise selected area diffraction. The spatially Gaussian laser pulse generated a HAZ extending up to 3μm radially from the femtosecond laser irradiated region.

High-resolution investigations of ripple structures formed by femtosecond laser irradiation of silicon

“…Similar to observations at much higher intensity (and thus probable heat-affected zones) [ 23 ], weak surface modifications are observed as shown in Fig. 1 , even outside the ablated area.…”

“…Initial transmission electron microscopy (TEM) analysis of such patterns generated by femtosecond laser irradiation show that part of the material was transformed from crystalline to amorphous [ 18 , 19 ]. Other experiments, not considering nanostructure formation, showed that irradiation by ultrafast laser pulses can result in both amorphization of crystalline material [ 20 – 23 ] and crystallization from the amorphous state [ 24 ]. Also, μ-Raman spectroscopy of femtosecond laser ablated Si surface revealed the generation of both amorphous and more complicated (high-pressure) phases of crystalline silicon [ 4 , 5 , 25 ].…”

Dislocation injection in strontium titanate by femtosecond laser pulses

“…Conversely, for materials exhibiting less plastic anisotropy, damage would be expected to be much more homogeneous because the critical resolved shear stresses would not vary as strongly from grain to grain. The magnitude and extent of the temperature profile immediately below the surface will vary with materials and experimental conditions, 6,8,[39][40][41] including laser ablation fluence, sample thickness, and orientation of laser beam to the sample surface.…”

Effects of Ultrashort Pulsed Direct Laser Writing on Ni/Al Reactive Multilayer Foils

“…Studies on thermal effects caused by femtosecond irradiation are mostly theoretical, and only a few experimental works are available on understanding the effect of USP irradiation on the HAZ [4,39]. Previous works have estimated the width of the HAZ when irradiating aluminum and titanium alloy with femtosecond pulses to be less than 2 µm [40][41][42].…”