Influence of synthesis conditions on optical and electrical properties of CaTiO3:Pr3+ thin films deposited by radiofrequency sputtering for electroluminescent device

CaTiO₃:Pr³⁺ is a phosphor of great interest for electroluminescence application owing to its intense red emission characterized by CIE coordinates very close to those of the NSTC “ideal red”. In this paper, thin films of CaTiO₃:Pr³⁺ are deposited by radiofrequency sputtering technique in pure argon and post-treated by Rapid Thermal Annealing (RTA). The influence of the deposition pressure (0.125–4.5 Pa) and annealing conditions on the optical and electrical properties of the thin films is investigated. The chemical composition of the as-deposited films, checked by Rutherford Backscattering Spectroscopy (RBS), is close to that of the ceramic target used for the deposition. The crystal structure is confirmed to be orthorhombic by X-ray diffraction. We highlight an improvement of the optical and electrical properties of the films after RTA treatment. Moreover, a net gain is obtained by comparison with conventional thermal treatment procedures in classical furnaces, especially for the reduction of electrical defect densities.     

In situ semi-quantitative analysis of polluted soils by laser-induced breakdown spectroscopy (LIBS)

Time-saving, low-cost analyses of soil contamination are required to ensure fast and efficient pollution removal and remedial operations. In this work, laser-induced breakdown spectroscopy (LIBS) has been successfully applied to in situ analyses of polluted soils, providing direct semi-quantitative information about the extent of pollution. A field campaign has been carried out in Brittany (France) on a site presenting high levels of heavy metal concentrations. Results on iron as a major component as well as on lead and copper as minor components are reported. Soil samples were dried and prepared as pressed pellets to minimize the effects of moisture and density on the results. LIBS analyses were performed with a Nd:YAG laser operating at 1064 nm, 60 mJ per 10 ns pulse, at a repetition rate of 10 Hz with a diameter of 500 μm on the sample surface. Good correlations were obtained between the LIBS signals and the values of concentrations deduced from inductively coupled plasma atomic emission spectroscopy (ICP-AES). This result proves that LIBS is an efficient method for optimizing sampling operations. Indeed, "LIBS maps" were established directly on-site, providing valuable assistance in optimizing the selection of the most relevant samples for future expensive and time-consuming laboratory analysis and avoiding useless analyses of very similar samples. Finally, it is emphasized that in situ LIBS is not described here as an alternative quantitative analytical method to the usual laboratory measurements but simply as an efficient time-saving tool to optimize sampling operations and to drastically reduce the number of soil samples to be analyzed, thus reducing costs. The detection limits of 200 ppm for lead and 80 ppm for copper reported here are compatible with the thresholds of toxicity; thus, this in situ LIBS campaign was fully validated for these two elements. Consequently, further experiments are planned to extend this study to other chemical elements and other matrices of soils.