Ahmed Youssef

A. Youssef

My general area of expertise is experimental physics. The following is an outline of my research  activities and interests;

• My main research interests are in the areas of superconductivity and magnetism. Finding a model to describe the experimental data in superconducting materials is a difficult task, so I have studied the critical state response in type II superconductors (i.e 2nd generation of HTS wires, coated YBCO thin film conductors [1], bulk NEG-123 sample[2] and Nb thin films [2, 3]). Using a Fourier analysis of the magnetic moment measured with a noncommercial continuous reading SQUID magnetometer in an applied ac field. We proved experimentally a validity of the Clem-Sanchez model for a response of circular disks in the Bean critical state (BCS) to a perpendicularly applied time varying magnetic field. I have developed a method of contactless determination of the critical depinning current density in hard type II superconductors[1-3]. This method is based on the analytical solutions of the BCS models to disk, strip, slab and cylinder. We proved the importance of the finding of behaviour of the higher harmonics when choosing a theoretical model to fit the experimental data. Although there is small difference between the theoretical and experimental fundamental susceptibility, the error in the estimated critical current density is high.

• ZnO is fuelled and fanned by prospects of its applications in optoelectronics owing to its direct wide bandgap, large exciton binding energy, and efficient radiative recombination. I have prepared Nano-Zinc Oxide thin films to study their structural, optical and electrical properties to explore their ability to be used as photoelectrode material or active absorber layer in solar cells. The obtained thin films have been characterized by preliminary structural investigation using different techniques in order to explore their structural and morphological properties and ensure the best quality of the prepared films. Optical, electrical and transport properties of the prepared thin films have been studied, and several structure parameters have been extracted. Furthermore, the effect of electrode type on the carrier transport properties and the associated electrical mechanisms will be investigated. This project is in progress. It is currently funded by Shaqra University in Saudi Arabia

• I have investigated the effect of adding of various filling levels from FeCl3 [4], AgNO3 [5], and mixtures of two transition compounds (X)AgNO3 (10-X)M, where M = FeCl3 [6] and  MnCl2 [7], on the  structure  and physical properties of polystyren films. The samples were prepared by the casting method, where X can take diffrent values from 0 to 10 %. The prepared films were studied by X-ray diffraction, infrared, DC electrical resistivity measurments, DC magnetic susceptibility and electron spin resonance.

References

[1]           A. Youssef, Z. Svindrych, and Z. Janu, “Analysis of magnetic response of critical state in second-generation high temperature superconductor YBa2Cu3Ox wire,” Journal of Applied Physics, vol. 106, no. 6, pp. -, Sep 15, 2009.

[2]           A. Youssef, “Critical state response in hard type II superconductors  (comparison of transverse and longitudinal geometries),” Department of Low Temperature Physics, Faculty of Mathematics and Physics, Charles University, Prague, 2011.

[3]           A. Youssef, Z. Svindrych, J. Hadac, and Z. Janu, “Analysis of critical state response in thin films by AC susceptibility measurements,” Ieee Transactions on Applied Superconductivity, vol. 18, no. 2, pp. 1589-1592, Jun, 2008.

[4]           A. Tawansi, A. El-Khodary, and A. Youssef, “Evolution of the physical properties of FeCl3 filled polystyrene films,” International Journal of Polymeric Materials, vol. 54, no. 7, pp. 557-574, 2005.

[5]           A. El-Khodary, A. Oraby, and A. Youssef, “The effect of AgNO3 filler on the physical properties of polystyrene films,” International J. of Mat. Sci, vol. 3, no. 1, pp. 11-24, 2008.

[6]           A. Tawansi, A. El-Khodary, and A. Youssef, “Structural, electrical and magnetic properties of polystyrene films filled with AgNO3–FeCl3 mixed fillers,” Journal of magnetism and magnetic materials, vol. 283, no. 2-3, pp. 199-209, 2004.

[7]           A. Tawansi, A. El‐Khodary, A. Oraby, and A. Youssef, “Effect of AgNO3–MnCl2 mixed fillers on the physical properties of polystyrene films,” Journal of applied polymer science, vol. 95, no. 6, pp. 1333-1341, 2005.