3 results
Search Results
Now showing 1 - 3 of 3
Article Citation - WoS: 4Citation - Scopus: 5Gd and Tb Doping Effects on the Physical Properties of Nd2sn2<(Elsevier Sci Ltd, 2018) Saleh, Adli A.; Hamamera, Hanan Z.; Khanfar, Hazem K.; Qasrawi, A. F.; Yumusak, G.In the current study, we report the light doping effects of the gadolinium and the terbium on the structural, morphological, optical and electrical properties of Nd2Sn2O7 pyrochlore ceramics. The pyrochlore which is prepared by the conventional solid state reaction technique is analyzed by means of scanning electron microscopy, energy dispersive X-ray analyzer, X-ray diffraction, ultraviolet- visible light spectrophotometry and temperature dependent current -voltage characteristics techniques. It is found that even though the doping content of both metals is low (2%), they significantly alter the physical properties of the pyrochlore. Particularly, it is observed that, these two doping agents increases the lattice parameter and strain and reduces the crystallite size and dislocation density. Optically, the effect of Gd doping on shrinking the energy band gap value of the Nd(2)Sn(2)O(7 )pyrochlore ceramic is more pronounced than that of Tb. On the other hand, the electrical investigations have shown that while the Gd make the pyrochlore exhibit p-type conductivity through forming shallow acceptor levels, the Tb forces n-type conductivity by forming deep donor levels below the conduction band edge. Such acceptor and donor impurity levels increases the electrical conductivity of the Nd(2)Sn(2)O(7 )pyrochlore ceramics by 390 and 58 times, respectively.Article Citation - WoS: 7Citation - Scopus: 7In situ monitoring of the permanent crystallization, phase transformations and the associated optical and electrical enhancements upon heating of Se thin films(Elsevier Science Bv, 2019) Qasrawi, A. F.; Aloushi, Hadil D.In this work, the in situ structural transformations from amorphous to polycrystalline upon heating and the associated enhancements in the structural parameters of selenium thin films are studied by means of X-ray diffraction technique. The Se thin films which are grown onto ultrasonically cleaned glass substrate by the thermal evaporation technique under vacuum pressure of 10(-5) mbar exhibits structural transformation from amorphous to polycrystalline near 353 K. The films completed the formation of the structure which includes both of the hexagonal and monoclinic phases at 363 K. It is observed that the hexagonal phase dominates over the monoclinic as temperature is raised. Consistently, the thermally assisted crystallization process is accompanied with increase in the crystallite size, decrease in the microstrain, decrease in defect density and decrease in the percentage of stacking faults. The scanning electron microscopy measurements also confirmed the crystallinity of selenium after heating. The time dependent reputations of the crystallization test has shown that the achieved phase transitions and enhancements in structural parameters are permanent in selenium. Optically, the crystallization process is observed to be associated with redshift in the absorption spectra and in the value of the energy band gap. Electrically, the in situ monitoring of the electrical conductivity during the heating cycle has shown that the electrical conductivity stabilizes and exhibit a decrease in the acceptor levels from 566 to 321 meV after the crystallization was achieved.Article Citation - Scopus: 11Cd-Doping Effects on the Properties of Polycrystalline Α-In2se3 Thin Films(2002) Qasrawi,A.F.The X-ray diffraction has revealed that the polycrystalline hexagonal structured α-In2Se3 thin films grown at substrate temperature of 200°C with the unit cell parameters a=4.03°A and c=19.23°A becomes polycrystalline hexagonal structured InSe with a unit cell parameters of a=4.00°A and c=16.63°A by Cd-doping. The analysis of the conductivity temperature dependence in the range 300-40 K revealed that the thermionic emission of charged carriers and the variable range hopping are the predominant conduction mechanism above and below 100 K, respectively. Hall measurements revealed that the mobility is limited by the scattering of charged carriers through the grain boundaries above 200 K and 120 K for the undoped and Cd-doped samples, respectively. The photocurrent (Iph) increases with increasing illumination intensity (F) and decreasing temperature up to a maximum temperature of ∼100 K, below which Iph is temperature invariant. It is found to have the monomolecular and bimolecular recombination characters at low and high illumination intensities, respectively. The Cd-doping increases the density of trapping states that changes the position of the dark Fermi level leading to the deviation from linearity in the dependence of Iph on F at low illumination intensities.
