Laser irradiation of 10x(Ni/Ti)/Si multilayers at different wavelengths

A study of the effects of laser irradiation on the morphology and composition of Ni/Ti multilayers induced by nanosecond laser pulses at different wavelengths is reported. Irradiation of complex 109(Ni/Ti)/Si sample was done by a Nd:YAG laser which operate at a 1064 nm wavelength, frequency doubled wavelength (532 nm) and dual-wavelength (1064 and 532 nm). The following surface morphological changes were observed: (1) ablation of the thin film during the first laser pulse and (2) appearance of some nanostructures (mosaic structure) in the irradiated region. After action of one pulse, the boundary of damage area was relatively sharp at low pulse energy, whereas it was diffuse after irradiation with higher energy per pulse. The results obtained show that laser irradiation induced mixing between Ni and Ti layers which creates conditions for the formation of intermetallic compounds. A numerical model was used to predict ablation depths and temperatures inside the material during the time. The model prediction shows a close agreement with experimental data

Laser-induced structural and composition modification of multilayered Ni/Ti thin film in air and liquids

The interaction of an Er, Yb, Cr-glass laser, operating at 1540 nm wavelength and a pulse duration of 40 ns, with Ni/Ti multilayer thin films has been studied. Five (Ni/Ti) bilayers deposited by DC ion sputtering on Si(100) wafers to a total thickness of about 180 nm were treated with laser fluences of about 6.4 and 8.8 J cm(-2). Single and multi-pulse laser irradiation was done at normal incidence in air, water and ethanol ambients. The composition and surface morphology were monitored by particle-induced x-ray emission, Rutherford backscattering spectrometry (RBS), scanning electron microscopy and profilometry. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the target surface. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. RBS analysis revealed that laser modification induced inter-mixing between the components of individual Ni and Ti layers, with indications of the formation of NiTi intermetallic compounds. An interesting finding is the morphological changes dominant in the Si substrate, whereas the Ni/Ti multilayer structure has mainly undergone changes in the chemical composition

Inducing subwavelength periodic nanostructures on multilayer NiPd thin film by low-fluence femtosecond laser beam

During femtosecond interaction with surfaces, the processes of liquid and solid-state dewetting could be responsible for the generation and regrouping of nanoparticles and nanoparticle clusters. The occurrence of surface plasmon polariton most probably induces the LIPSS arrangement. We have used low-fluence scanning femtosecond beam to generate sub-wavelength periodic structures on multilayer Ni/Pd thin films on Si. The spatial period of LIPSS increases with the change of scanning directions in respect to the polarization direction due to the phase difference increase between the incoming and induced oscillations. (c) 2017 Elsevier B.V. All rights reserved.10th International Conference on Photo-Excited Processes and Applications (ICPEPA), Aug 29-Sep 02, 2016, Transilvania Univ Brasov, Brasov, Romani

Luminescence thermometry via the two-dopant intensity ratio of Y2O3: Er3+, Eu3+

In this work we investigated the photoluminescence properties of Y2O3: Er3+, Eu3+ as a function of temperature and the possibility to use this material as a temperature sensor. Photoluminescence emission measurements with 532 nm laser excitation were recorded in the temperature range from 303 up to 573 K. The measured intensity ratio of erbium S-4(3/2) - GT I-4(15/ 2) and europium D-5(0) - GT F-7(2) emission lines was used for determination of the temperature calibration curve. These emission lines are intense, narrow and well defined. The distance between the lines, being 47 nm, can be easily measured even with a low-resolution spectrometer. The calculated relative sensitivity of the temperature sensor was 1.4% K-1 at 303 K, in the physiological temperature range, meaning that it could be successfully applied in biological studies

Agglomeration in core-shell structure of CuAg nanoparticles synthesized by the laser ablation of Cu target in aqueous solutions

Metallic copper Cu and bimetallic copper-silver CuAg nanoparticles (NPs) are generated by the ablation of copper bulk target in water and aqueous Ag colloidal solution, respectively. The experiments were performed using nanosecond Nd: YAG laser operating at 1064 nm. The generated NPs are characterized by UV-vis absorption spectroscopy, laser-induced breakdown spectroscopy, dynamic light scattering and scanning electron microscopy. The conducted investigations can be summarized as follows: (i) CuAg NPs colloidal solution possess the absorption in UV-vis spectral region, which can be attributed to the Cu-component; (ii) the primary bimetallic CuAg NPs have near uniform dimensions with diameter of about 15 nm, and as a rule, they are grouped into larger agglomerates without defined morphology; (iii) the obtained Cu NPs have mainly spherical form with average diameters up to 20 nm. Both types of NPs show a tendency towards the formation of large agglomerates with different morphology. Bimetallic NPs show the plasmon resonance in the vicinity of 640 nm with a good coincidence with formation of the colloidal solution of pure Cu NPs. The results also demonstrate that the core-shell structure (Ag-rich core/Cu-rich shell) is important for the formation of the bimetallic NPs, also agreeing very well with theory

Surface modification of Ti-based nanocomposite multilayer structures by using laser beam irradiation

A study of the effects of laser irradiation on the morphology and structure of Al/Ti and Ni/Ti multilayers is reported in this paper. Multilayers of Al/Ti and Ni/Ti were deposited by dc ion sputtering on Si(100) substrates in a single vacuum run. Laser processing was done by a focused Er, Yb, Cr glass laser beam at a wavelength of 1540 nm, a pulse duration of 40 ns and fluence in the range 8.5-23.8 J cm(-2). Surface changes can be summarized as follows: (i) the intensive removal of surface material with crater-like characteristics, (ii) the appearance of hydrodynamic features (such as resolidified droplets) and (iii) the sporadic appearance of cracking. Changes in the (Ni/Ti)/Si system included modification of the Si substrate with the formation of polygonal-mosaic structures and the appearance of hydrodynamic features in the form of nano-globules. The rate of ablation increased with energy density, whereas the rate of ablation for the (Ni/Ti)/Si system (similar to 11 x 10(3) mu m(3) per pulse) was higher than that for the (Al/Ti)/Si system (similar to 7 x 10(3) mu m(3) per pulse).3rd International School and Conference on Photonics, Aug 29-Sep 02, 2011, Belgrade, Serbi

Laser induced damage/ablation morphology on the 8(Al/Ti)/Si system in different ambient conditions

A study of morphological and composition changes of the (8(Al/Ti)/Si) system induced by laser pulses in different ambient conditions is presented. The effects of an Er, Yb, Cr-Glass laser, operating at 1540 nm wavelength with pulse duration of 44 ns, on a complex target were investigated. Irradiation of 8(Al/Ti)/Si was carried out at intensities of 5.9 and 9.5 x 10(11) W m(-2) in air, water and ethanol. The laser-induced morphological and composition modifications have shown dependence on applied intensities, number of laser pulses and ambient conditions. The following morphological changes were observed: (i) intense surface melting of the thin film and Si-substrate; (ii) ablation/exfoliation of the 8(Al/Ti) multilayer thin film from Si, (iii) appearance of hydrodynamic features such as resolidified material, and (iv) formation of crater at multi-pulse action. The formation of parallel periodic surface structure was only occurring in single pulse air-assisted modification. Analysis of the composition revealed that laser modification induced intermixing between the components of individual Al and Ti layers with potential formation of AlTi intermetallic compounds. (C) 2013 Elsevier Ltd. All rights reserved

Surface nanopatterning of Al/Ti multilayer thin films and Al single layer by a low-fluence UV femtosecond laser beam

The effects of UV femtosecond laser beam with 76 MHz repetition rate on two types of thin films on Si substrate - the Al single layer thin film, and the multilayered thin film consisted of five Al/Ti bilayers (total thickness 130 nm) - were studied. The surface modification of the target was done by low fluences and different irradiation times, not exceeding similar to 300s. Nanopatterns in the form of femtosecond-laser induced periodic surface structures (fs-LIPSS) with periodicity of LT 315 nm and height of 45 nm were registered upon irradiation of the thin films. It was shown that: (i) the fs-LIPSS evolve from ruffles similar to high spatial frequency LIPSS (HSFL) into a low spatial frequency LIPSS (LSFL) if a certain threshold of the fluence is met, (ii) the number of LSFL increases with the exposition time and (iii) the LSFL remain stable even after long exposure times. We achieved high-quality highly-controllable fabrication of periodic structures on the surface of nanosized multilayer films with high-repetition-rate low-fluence femtosecond laser pulses. Compared to the Al single layer, the presence of the Ti underlayer in the Al/Ti multilayer thin film enabled more efficient heat transmittance through the Al/Ti interface away from the interaction zone which caused the reduction of the ablation effects leading to the formation of more regular LIPSS. The different outcomes of interactions with multi and single layer thin films lead to the conclusion that the behavior of the LIPSS is due to thin film structure. (C) 2014 Elsevier B.V. All rights reserved