Gaković, B.; Petrović, S.; Siogka, C.; Milovanović, D.; Momčilović, M.; Tsibidis, G.D.; Stratakis, E.

The interaction of ultra-short laser pulses (USLP) with Nickel/Titanium (Ni/Ti) thin film has been presented. The nano layer thin film (NLTF), composed of ten alternating Ni and Ti layers, was deposited on silicon (Si) substrate by ion-sputtering. A single and multi-pulse irradiation was performed in air with focused and linearly polarized laser pulses. For achieving selective ablation of one or more surface layers, without reaching the Si substrate, single pulse energy was gradually increased from near the ablation threshold value to an energy value that caused the complete removal of the NLTF. In addition to single-pulse selective ablation, the multi-pulse USLP irradiation and production of laser-induced periodic surface structures (LIPSSs) were also studied. In the presented experiment, we found the optimal combination of accumulated pulse number and pulse energy to achieve the LIPSS formation on the thin film. The laser-induced morphology was examined with optical microscopy, scanning electron microscopy, and optical profilometry. To interpret the experimental observations, a theoretical simulation has been performed to explore the thermal response of the NLTFs after irradiation with single laser pulses.The interaction of ultra-short laser pulses (USLP) with Nickel/Titanium (Ni/Ti) thin film has been presented. The nano layer thin film (NLTF), composed of ten alternating Ni and Ti layers, was deposited on silicon (Si) substrate by ion-sputtering. A single and multi-pulse irradiation was performed in air with focused and linearly polarized laser pulses. For achieving selective ablation of one or more surface layers, without reaching the Si substrate, single pulse energy was gradually increased from near the ablation threshold value to an energy value that caused the complete removal of the NLTF. In addition to single-pulse selective ablation, the multi-pulse USLP irradiation and production of laser-induced periodic surface structures (LIPSSs) were also studied. In the presented experiment, we found the optimal combination of accumulated pulse number and pulse energy to achieve the LIPSS formation on the thin film. The laser-induced morphology was examined with optical microscopy, scanning electron microscopy, and optical profilometry. To interpret the experimental observations, a theoretical simulation has been performed to explore the thermal response of the NLTFs after irradiation with single laser pulses.

F. Capone, O. Muntada, J. C. Ramírez, M. J. Esplandiu et al.

We present first hard X-ray photoelectron spectroscopy (HAXPES) results of aqueous salt solutions and dispersions of gold nanoparticles in liquid cells equipped with specially designed microfabricated thin silicon nitride membranes, with thickness in the 15–25 nm range, mounted in a high-vacuum-compatible environment. The experiments have been performed at the HAXPES endstation of the GALAXIES beamline at the SOLEIL synchrotron radiation facility. The low-stress membranes are fabricated from 100 mm silicon wafers using standard lithography techniques. Platinum alignment marks are added to the chips hosting the membranes to facilitate the positioning of the X-ray beam on the membrane by detecting the corresponding photoemission lines. Two types of liquid cells have been used, a static one built on an Omicron-type sample holder with the liquid confined in the cell container, and a circulating liquid cell, in which the liquid can flow in order to mitigate the effects due to beam damage. We demonstrate that the membranes are mechanically robust and able to withstand 1 bar pressure difference between the liquid inside the cell and vacuum, and the intense synchrotron radiation beam during data acquisition. This opens up new opportunities for spectroscopic studies of liquids.

C. Romanitan, J. M. Caicedo, R. Pascu, et al.

In this paper, pulsed laser deposition (PLD) at low partial oxygen pressure(similar to 10 mTorr) was used to obtain VO2 thin films. During the PLD, the deposition temperature and number of pulses were varied in order to obtain a good sample crystallinity. It was showed by atomic force microscopy(AFM) micrographs that the mean grain size increasedfrom similar to 40 nm to similar to 90 nm at a variation of the deposition temperature from 400(degrees)C to 500(degrees)C.Further, by increasing of both substrate temperature and number of pulses, the mean grainsize increases to 220 nm. According to the Rietveld refinement of the experimental X-ray diffraction(XRD) pattern, within the grain size increasing, the mean crystallite size increased from 14 nm to 22 nm, as well as a decreasing of the lattice strain from 0.29% to 0.20%.These dependencies further imply a decreasing of the dislocation density of 2.3 to0.9x10(12)cm(-2). At the same time, the optical band gap decreased from 0.72 eV (400(degrees)C) to0.66 eV (500(degrees)C), reaching 0.60 eV (600(degrees)C). Further investigations performed by X-ray photoelectron spectroscopy(XPS) showed the vanadium oxide presence, by the spin-orbit splitting of approximately 7.5 eV betweenV2(p3/2)andV2(p1/2)orbitals. Finally, the electrical measurements done in the range of 250-370K reveal a close relationship between the dislocation density and the observed resistance-temperature dependence.