Papers by Author: S. Malek

Abstract: In this work, the combined diagnostic measurements of ablated material by scanning electron microscopy of the craters and ion time of flight analysis have been employed to study the interaction of third harmonic Nd-Yag laser with silicon and titanium target. Evidence for the transition from normal vaporization to phase explosion has been obtained, showing an abrupt increase in the mass ablation rate beyond a laser intensity threshold and round-shaped micrometer-sized cavities found on the irradiated areas. Ion time of flight analysis is used to estimate the surface temperature under near threshold ablation conditions.

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.