New trends in femtosecond Pulsed Laser Deposition and femtosecond produced plasma diagnostics

International audienceThe availability of compact table top amplified femtosecond lasers and the technical simplicity of experimental design have opened the way to many recent and fast developments towards thin film elaboration by Pulsed Laser Deposition (PLD) with ultra short laser pulses, with the aim of producing materials of high quality previously unattainable or attainable only through more complex means. The first developments of PLD using femtosecond lasers were made on Diamond-Like Carbon thin films elaboration, with the attempt to reach high sp3 content. PLD with ultra short pulses was used recently to deposit several systems such as quasicrystals or oxides with a transfer of the target composition to the deposited films, even for compounds with complex stoechiometry. Femtosecond laser ablation from solid targets has shown its capability in producing nanoparticles of different materials, even in high vacuum conditions. Nanostructured films of doped Diamond-Like Carbon were obtained recently, opening the way to large applications towards functional materials. The characteristics of the plasma are a well-suited signature of the physics of laser-matter interaction and plasma plume creation and expansion. Recent studies on the control of the film growth and femtosecond PLD processes will be reported. Emphasis on actual capability of the existing sources to elaborate high quality materials will be questioned in terms of energy per pulse, time width, repetition rates but also in the need for further source development and beam shaping improvement

Theory of magnetic domains in uniaxial thin films

For uniaxial easy axis films, properties of magnetic domains are usually described within the Kittel model, which assumes that domain walls are much thinner than the domains. In this work we present a simple model that includes a proper description of the magnetostatic energy of domains and domain walls and also takes into account the interaction between both surfaces of the film. Our model describes the behavior of domain and wall widths as a function of film thickness, and is especially well suited for the strong stripe phase. We prove the existence of a critical value of magneto-crystalline anisotropy above which stripe domains exist for any film thickness and justify our model by comparison with exact results. The model is in good agreement with experimental data for hcp cobalt.Comment: 15 pages, 7 figure

Is positive communication sufficient to modulate procedural pain and anxiety in the emergency room? A randomized controlled trial.

Research suggests that therapeutic communication could enhance patient comfort during medical procedures. Few studies have been conducted in clinical settings, with adequate blinding. Our hypothesis was that a positive message could lead to analgesia and anxiolysis, and that this effect would be enhanced by an empathetic interaction with the nurse performing the procedure, compared to an audio-taped message. This study aimed to modulate the contents and delivery vector of a message regarding peripheral intravenous catheter (PIC) placement in the emergency room (ER). This study was a 2 + 2 randomized controlled trial registered on clinicaltrials.gov (NCT03502655). A positive versus standard message was delivered through audio tape (double blind) in the first phase (N = 131) and through the nurse placing the catheter (single blind) in the second phase (N = 120). By design, low practitioner empathic behavior was observed in the first phase (median 1 out of 5 points). In the second phase, higher empathic behavior was observed in the positive than in the standard message (median 2 vs. 3, p < 0.001). Contrary to our hypothesis, the intervention did not affect pain nor anxiety reports due to PIC placement in either phase (all p values>0.2). The positive communication intervention did not impact pain nor anxiety reports following PIC. There might have been a floor effect, with low PIC pain ratings in a context of moderate pain due to the presenting condition. Hence, such a therapeutic communication intervention might not be sufficient to modulate a mild procedural pain in the ER

Graphene-based textured surface by pulsed laser deposition as a robust platform for surface enhanced Raman scattering applications

International audienceWe have developed a surface enhanced Raman scattering (SERS)-active substrate based on gold nanoparticles-decorated few-layer (fl) graphene grown by pulsed laser deposition. Diamond-Like Carbon film has been converted to fl-graphene after thermal annealing at low temperature. The formation of fl-graphene was confirmed by Raman spectroscopy, and surface morphology was highlighted by scanning electron microscopy. We found that textured fl-graphene film with nanoscale roughness was highly beneficial for SERS detection. Rhodamine 6G and p-aminothiophenol proposed as test molecules were detected with high sensitivity. The detection at low concentration of deltamethrin, an active molecule of a commercial pesticide was further demonstrated

Unconventional magnetism in all-carbon nanofoam

We report production of nanostructured carbon foam by a high-repetition-rate, high-power laser ablation of glassy carbon in Ar atmosphere. A combination of characterization techniques revealed that the system contains both sp2 and sp3 bonded carbon atoms. The material is a novel form of carbon in which graphite-like sheets fill space at very low density due to strong hyperbolic curvature, as proposed for ?schwarzite?. The foam exhibits ferromagnetic-like behaviour up to 90 K, with a narrow hysteresis curve and a high saturation magnetization. Such magnetic properties are very unusual for a carbon allotrope. Detailed analysis excludes impurities as the origin of the magnetic signal. We postulate that localized unpaired spins occur because of topological and bonding defects associated with the sheet curvature, and that these spins are stabilized due to the steric protection offered by the convoluted sheets.Comment: 14 pages, including 2 tables and 7 figs. Submitted to Phys Rev B 10 September 200