Papers by Author: Slimane Lafane

Abstract: In this contribution we study the effect of the laser fluence on the stoichiometry, morphology and density of Sm1-xNdxNiO3 thin films. The latter were grown by a KrF excimer laser (λ = 248 nm, τ = 25 ns) ablation of a rotating target onto unheated (100) silicon substrates for 9000 pulses at different laser fluences into vacuum. The target used was a mixture of samarium, neodymium and nickel oxides. The relative ratio of neodymium (x = 0.45) is set to have a transition temperature close to room temperature (TMI = 310 K). The target-substrate distance was maintained at 4 cm. The composition and the morphology of the deposited layers were analysed by energy dispersion X-ray spectroscopy (EDX) and scanning electron microscope (SEM) respectively. It was found that films properties depend strongly on the laser fluence. The EDX measurements revealed that the laser fluence must be higher than 1 Jcm-2 for a congruent evaporation. However, even at this condition, the films were deficiency in oxygen. The morphology study showed that the films surface was widely contaminated by droplets for fluences superior to 2 Jcm-2. Also, it was found that by increasing laser fluence the films density increases and reach a plateau at 1.3 Jcm-2. According to all those elements, the laser fluence was set to be in the range of 1.3 – 2 Jcm-2.

Abstract: Carbon nitride films were synthesized by pulsed laser ablation of graphite target under nitrogen ambience. The third harmonic of a pulsed Nd-YAG laser of 355 nm wavelength and 7 ns pulse duration was focused onto a rotating target at an incidence angle of 45°. The laser fluence at the target surface was set at 30 J/cm2. The carbon nitride films were deposited on (100) silicon substrate kept at room temperature and placed at a distance of 40 mm from the target surface. The CNx films were grown under N2 gas in the pressure range of 5×10-3 to 4×10-1 mbar. The deposited films composition was investigated by different techniques RBS, NRA and AES. We found an N/C ratio equal to 0.4 in the pressure range cited above.

Abstract: The perovskites RNiO3 (R rare earth ≠ La) are classified as a phase transition metal-insulator. The transition temperature is modulated by the size of the rare earth. The use of compound R1-xR'xNiO3 can vary transition temperature on a wide thermal range depending on the concentration of the two rare earths. The Sm1-xNdxNiO3 (x = 0.45) thin layers have been carried out on (100) silicon substrates by KrF laser ablation (λ = 248 nm, 25ns) at two different fluences 2 and 3 Jcm-2. The oxygen pressure and the target-substrate distance have been maintained at 0.2 mbar and 4 cm respectively. The deposition temperature has been set at 500 ° C. The obtained layers were characterized by X-ray diffraction, atomic force microscopy and Rutherford back scattering diagnostics. The resistivity Measurements were carried out by the conventional four-probe method. The XRD spectra revealed the presence of an ideal cubic perovskite phase. The RBS analysis showed that the deposited layers are rich in oxygen. A correlation between the morphology properties of the deposited layers and the plasma dynamics studied by fast imaging has been found.