Publications Internationales
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Item The effect of doping with rare earth elements (Sc, Y, and La) on the stability, structural, electronic and photocatalytic properties of the O-termintaed ZnO surface; a first-principles study(Elsevier, 2018) Lahmer, Mohammed AliThe effect of doping with rare earth atoms (Sc, Y, and La) on the stability, structural, electronic, and photocatalytic properties of the O-terminated ZnO surface was investigated by using the first-principles method. The obtained results show that all these elements have negative formation energies for all possible values of the oxygen chemical potential, and this means that the doping process with RE atoms (RE = Sc, Y, and La) enhances the stability of this surface. Our results show also that, among all considered elements, the Sc atoms have the lowest formation energy followed by Y and La, respectively. We have also investigated the effect of the formation of a RE-VO complex on the properties of the ZnO surfaces. We find that the formation of a RE-VO complex is energetically more favored than the formation of isolated REZn defect under Zn-rich conditions. The effect of the formation of both REZn and RE-VO defects on the electronic and photocatalytic properties of the O-terminated ZnO surface was studied in details and the obtained results show that the RE-VO complex may be the origin of the photocatalytic properties enhancement of the doped surfaces. Moreover, we found that the Sc-doped surface prepared under Zn rich conditions may have the best photocatalytic properties followed by Y- and La-doped surfaces, respectively.Item First-principles study of the structural, electronic, and optical properties of the clean and O-deficient ZnAl2O4(110) surfaces(Elsevier, 2018) Lahmer, Mohammed AliIn this work, the stability, structural, electronic, and optical properties of the ZnAl2O4(110) surface have been investigated by using the first-principles method based on the density functional theory. The obtained results show that the AlO2-terminated surface is more stable than the ZnAlO2-terminated surface under O-rich and Al-poor conditions, while the ZnAlO2 surface termination is the most stable under O-poor and Al-rich conditions. The results of structural relaxation show that, for both surface terminations, the most noticeable change in the interlayer distances occurs in the four outermost layers only. In addition, our results also show that the electronic structure and properties of these two surfaces are very different. The work function of the ZnAlO2-terminated surface was found to be 2 times smaller than that of the AlO2 surface. Moreover, the effect of oxygen vacancies on the properties of the ZnAl2O4(110) polar surfaces was investigated in details. We find that the formation energy of VO in the case of the AlO2-terminated surface is lower than that of the ZnAlO2-terminated surface. Our results show that the formation of oxygen vacancies affects greatly the electronic and optical properties of the ZnAl2O4(110) surface. We found also that, at high temperatures, the O-deficient AlO2-terminated surface is more stable than the clean surface.Item First-principles study of the structural and electronic properties of the clean and O-deficient ZnAl2O4(111) surfaces(Elsevier, 2019) Lahmer, Mohammed AliItem The effect of hydrogen adsorption on the properties of undoped and Cu-doped ZnO(101¯0) surfaces : a first-principles study(Elsevier, 2016) Lahmer, Mohammed AliItem Hydrogen sensing properties of the ZnO (0 0 0 1 ¯) surface enhanced by Be doping : a first principles study(Elsevier, 2015) Lahmer, Mohammed AliItem The effect of growth conditions, point defects and hydrogen on the electronic structure and properties of p-type (Al,N) codoped ZnO: A first principles study(Elsevier Ltd, 2015) Lahmer, Mohammed Ali; Guergouri, KAbstract The effects of point defects, hydrogen, and growth conditions on the electronic structure and properties of the (Al,N) codoped p-type ZnO have been investigated using the first principles method. The obtained results showed that the AlZn-NO-VZn complex is a shallow acceptor that can play an important role in achieving the p-type conductivity in the (Al,N) codoped ZnO films. Our results showed also that the electrical conductivity type in the (Al,N) codoped ZnO films strongly depends on the donor/acceptor concentrations ratio. The codoped ZnO films prepared under both Zn-rich and O-rich growth conditions with a donors/acceptors ratio of 1:2 have a p-type conductivity, while those prepared with a ratio of 1:1 cannot be p-type unless if they are prepared under O-rich conditions. The achieved p-type quality depends also on the used nitrogen doping source. To prepare p-type ZnO film of high quality using the (Al,N) codoping method, the use of NO or NO2 is recommended. The presence of donor defects such as oxygen vacancies and hydrogen will significantly affect the electronic properties of the (Al,N) codoped ZnO films, and if the concentration of these defects in the sample is high enough, the material can be easily converted to n-typeItem Effect of hydrogen adsorption on the electronic and optical properties of the Mg-doped O-terminated ZnO surface(Elsevier, 2015) Lahmer, Mohammed Ali; Guergouri, Kamel