An investigation of the structural, electronic and vibrational properties of magnesium chalcogenides

Key Words: MgS, MgSe, MgTe, density functional theory, electronic spectrum, band gap, phonons The aim of this thesis is to investigate structural, electronic and dynamical properties of magnesium chalcogenide materials by employing the plane-wave pseudopotential method, density functional theory and linear response technique. The reason for choosing this topic is that these materials can be crystallized in different crystal structures (such as rocksalt, zincblende, wurtzite and nickel arsenide) and can exhibit a wide range of electronic band gap. Due to these interesting properties there has been great interest in the study of structural and electronic properties of these semiconductors. These materials are promising in the blue colour spectrum with large band gap. Thus, it is important to determine structural, electronic and vibrational properties of these semiconductors in order to succesfully apply them to optoelectronic technology. In the introduction of this thesis, previous studies on these semiconductors have been cited. Moreover, we have explained the goal of this thesis. Then crystal structures of these semiconductors have been discussed in the second chapter. In the third chapter, experimental techniques for measuring electronic and phonon properties are explained. In the fourth chapter of this thesis, the plane-wave pseudopotential method, density functional theory and linear response technique are summarized. Then, the application of density functional theory to Mg-chalcogenides has been explained. In the fifth chapter, we have presented our structural results for rocksalt, zincblende, wurtzite and nickel arsenide phases of Mg-chalcogenides. Electronic results for these semiconductors are presented in the chapter six. After discussing electronic properties, vibrational properties of Mg-chalcogenides have been presented in chapter seven for the rocksalt phase, chapter eight for zincblende phase, chapter nine for wurtzite phase and chapter ten for nickel arsenide phase. This work is the first theoretical study on vibrational properties of Mg-chalcogenides in four different phases to the best of our knowledge. In the last chapter of this thesis, our results have been discussed as well as the possible future works.