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Abstract: This paper contributes to the old problem of droplet formation by providing detailed quantitative data on the population statistics of particulates deteriorating the surface of boron carbide films produced by PLD. Films of 180±30nm thicknesses have been fabricated by KrF excimer laser ablation of a sintered B4C target in high vacuum. Number densities and size distributions of the particulates are given for 14 films, deposited at laser fluences tuned between 2 and 14Jcm−2, as a result of evaluating SEM images of the same magnification taken from minimum five different areas (altogether (2–4)×10−2 mm2) of each film. The overwhelming majority of the droplets is small with diameters, d ≤1μm. The number density of those with d ≤0.5μm ranges from (1 to 7)×104 mm−2. The effect of gradual deterioration of the target surface as a result of prolonged irradiation screens practically totally the effect of changing fluence. The number of droplets of diameters in excess of 1μm increases linearly with increasing number of shots/site resulting in maximum surface coverage values as high as 36%. [Copyright &y& Elsevier]

A series of boron carbide films of 180±30 nm thickness has been deposited by KrF excimer laser ablation of a sintered B4C target in high vacuum. Rutherford backscattering spectroscopy revealed that the chemical composition of the films grown on Si substrates, at room temperature, at laser fluences tuned between 2 and 14.3 J cm−2 varied depending not only on the actual laser fluence but also on the past record of the B4C target. Parallel SEM mapping of both film and target surfaces pointed to a correlation between changes in film composition, droplet density and target surface deterioration. This correlation is discussed in detail. [Copyright &y& Elsevier]

We propose a low cost technique for the production of diffractive optical elements (DOE). These elements are devoted to high power lasers beam shaping in the mid-infrared wavelengths. This process called laser ablation lithography (LAL), may seem similar to laser beam writing (LBW) in the way the whole DOE’s design is reproduced pixel by pixel on the substrate placed on a computer controlled XY translation stage. A first difference is that the photoresist is not exposed with UV light but is directly ablated with short excimer laser pulses. Furthermore, with LAL technique the size of the smallest pixel (5 μm×5 μm) is more than 10 times greater than those produced by LBW. We discuss in details the experimental set-up for LAL and demonstrate that it gives a resolution up to 10 times greater than photolithography with flexible masks. This makes LAL a promising solution for the production of DOE for use with Nd:YAG lasers. New applications of DOEs are finally introduced with high power lasers sources, such as laser marking or multi-point brazing. [Copyright &y& Elsevier]

Carbon films have been deposited by ArF excimer laser ablation of a graphite target in argon ambient of pressures between 10−4 and 200 Pa. Besides carbon, ex situ RBS and ERDA measurements reveal the presence of argon, hydrogen and oxygen in the films. Below 0.5 Pa the apparent growth rate, defined as the measured thickness per number of pulses, is almost constant at around 0.30 A˚ per pulse. Between 0.5 and 5 Pa it drops to 0.15 A˚ per pulse. The most salient feature of the pressure dependence is the unexpected increase in the apparent growth rate between 5 and 100 Pa. Above 100 Pa the growth rate further decreases below 0.07 A˚ per pulse. Parallel AFM measurements reveal characteristic differences in the surface morphology in each domain. Comparative analysis of the dependence of parameters characteristic of film growth and the evolution of microstructure on argon pressure provides information on the growth mechanism up to 200 Pa. [Copyright &y& Elsevier]

Carbon nitride films deposited by ArF excimer laser ablation of a graphite target in the 1–100-Pa N2 pressure and 1.0–10-J cm−2 fluence domains differ not only in their nitrogen but also in their oxygen content. The (surface) oxygen content correlates well with the compactness of the films. Oxygen contents below approximately 8 at.%, smooth surface, and mass densities above 2.2 g cm−3 are typical of films deposited at low N2 pressures (and high fluences) while deposition at/above 50 Pa results in films of oxygen contents exceeding 12 at.%, rough surface consisting of loosely connected cluster agglomerates, and density values at approximately 1.4 g cm−3. At medium pressures high fluence processing is advantageous in terms of both nitrogen content and film morphology. [Copyright &y& Elsevier]

Results of a comparative XPS study on 26 carbon nitride samples of different chemical composition fabricated by ablating a graphite target with an ArF excimer laser in N2 atmosphere while systematically varying the pressure in the 1–100-Pa and the laser fluence in the 1.0–10-J cm−2 domains are reported. N1s core level spectra recorded on all samples are consistently fitted by four components at 398.2, 399.4, 400.7 and 402.1 eV, respectively. Changes in the relative abundance of the individual spectral components of the N1s lines as a function of laser fluence and nitrogen pressure are interpreted in terms of changes in the chemical environment around nitrogen atoms. When present in low concentration, nitrogen atoms prefer sites allowing pyramidal configuration. With increasing concentration more and more atoms form C&z.sbnd;N&z.dbnd6;C type bonds, nevertheless, in all films the majority of the nitrogen atoms occupies pyramidal configurations. [Copyright &y& Elsevier]

Carbon nitride films deposited onto room temperature silicon substrates by ArF excimer laser ablation of a graphite target in nitrogen atmosphere have been investigated after floating off in transmission electron microscope (TEM). All films fabricated in the 1–100 Pa N2 pressure and 1–10 J cm−2 fluence domain are amorphous. It is the nitrogen pressure that governs both the composition and the morphology of the films, the effect of the laser fluence being weaker. The morphologies range from dense films grown in 1–5 Pa N2, to structures composed of carbon nitride clusters and voids between them, obtained at and above 50 Pa N2. Ablation with pulses of high fluence (10 J cm−2) results in more compact films. The oxygen content determined by energy dispersive X-ray spectrometry well correlates with the compactness of the films, being significantly higher in those fabricated at higher pressures and composed of clusters. [Copyright &y& Elsevier]

Abstract. Diamond-like carbon (DLC) films have been grown on Si substrates at ambient temperature by the pulsed-laser ablation technique, using pulses of different durations both in the nano- and picosecond ranges and at various energy fluences. The stability of these films was investigated as a function of thermal anneals performed in UHV conditions up to 1273 K. Their physico-chemical properties have been characterized by different techniques including X-ray photoemission, Auger electron and electron-energy-loss spectroscopies, Raman scattering, spectroscopic ellipsometry and atomic-force microscopy. The thermal stability of the films has been demonstrated to be related to their initial structural (sp[sup 3]/sp[sup 2] ratio) and chemical (contaminant) properties. DLC layers prepared under optimized conditions have been found to show a very good thermal stability up to 900 K. [ABSTRACT FROM AUTHOR]

Abstract. Silicon-based thin films have been obtained by the direct photodissociation of mono- or disilane gases in a windowless CVD reactor using the vacuum ultraviolet (VUV) argon emission generated by electrical discharges. Atomic force microscopy, Raman scattering and elastic recoil detection analysis techniques were applied to characterize the surface morphology, the structural properties, and the hydrogen content of the deposits, respectively, as a function of the silicon hydride concentration in the feed gas and, to a lesser extent, of the substrate temperature. Independent of the hydride concentration, it is found that the layers have a low hydrogen content of the order of 5% to 10%. On the other hand, their surface roughness is limited to a few nanometers providing that the partial hydride gas pressure in the reactor does not exceed 10 Pa. Raman investigations show that two different types of material can be obtained: either a purely amorphous one for hydride concentrations not exceeding 10% or a mixture of Si submicrocrystals embedded in an amorphous medium for the higher concentrations. Given the conditions of the growth technique used and the photodissociation mechanisms involved, it is concluded that a homogeneous nucleation process occurs already within the gas phase, leading to the formation of nanosized Si grains, that may agglomerate before reaching the substrate where a further growing step eventually takes place. [ABSTRACT FROM AUTHOR]

Gonorrhoea cases increased steeply in women aged 20 to 24 years across 15 EU/EEA countries in July to December 2022 and January to June 2023 with, respectively, 73% and 89% more cases reported than expected, based on historical data from 2015 to 2019. Smaller increases among men due to heterosexual transmission were observed in nine EU/EEA countries. Interventions to raise awareness among young people about sexually transmitted infection risks are needed, emphasising the benefit of safe sexual practices and testing.

Paired associate learning performance and strategies were analyzed in terms of learning situations (training vs. 'contextual' and 'noncontextual' transfer), personality factors [Thrill and adventure seeking (TAS) and disinhibition (Dis)] and catecholamine enzyme activity [dopamine-beta-hydroxylase (DBH) and monoamine-oxydase (MAO)]. Performance was better in transfer situations, in high MAO-high DBH subjects (high catecholamine turnover rate?), and as a negative function of DBH (preponderance of dopaminergic activity?). Error patterns of response selection (high omission and low intrusion error rate) were found to be a positive function of contextual transfer, TAS and DBH (high response-contingent noradrenergic activity?).