Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.731351
Title: First-principles simulation of functional materials interfaces
Author: Ouserigha, Ebiyibo
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2017
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Abstract:
The epitaxial growth of functional materials onto semiconductor substrates have successfully driven new technologies and tailor materials properties over some decades. We report on the structural, electronic and magnetic properties of several interfaces between MnSb and the III-V semiconductors (InSb, InP and GaAs) as well as the semi-metal Sb, using spin-polarized density functional theory simulations. In addition, the low index oxide interfaces between NiO and MgO were studied. This work is motivated by the potential application of these material combinations in spintronics. Spin polarization at the interfaces between MnSb and non-magnetic materials (III-V semiconductors and a semi-metal) have been predominantly computed from density functional theory calculations. Initially, multilayers of zinc blende MnSb(111)/InSb(111) are investigated. The Mn-to-Sb termination of the interface between a zinc blende half-metallic ferromagnet, MnSb, with 100% spin polarization and InSb both in the (111) direction, is energetically more stable and maintains a high spin polarization of 92.6%. Spin polarization, which is usually reduced or destroyed at the interfaces of half-metallic ferromagnets, is seen to behave differently in the Mn-to-Sb termination of the MnSb(111)/InSb(111) interface structure. And this high spin polarization of 92.6% is injected into the first atomic layer of the InSb(111) slab, before reducing to 40.0% in the fourth atomic layer of the semiconductor slab. Then the interfaces between niccolite (n)-MnSb(0001) and InP(111) and GaAs(111) were studied in the following chapter. The studies of the n-MnSb(0001)/InP(111) and n-MnSb(0001)/GaAs(111) interfaces show that the Mn-to-P termination of the n-MnSb(0001)/InP(111) and Mn-to-As termination of the n-MnSb(0001)/GaAs(111) superlatices have an enhanced spin polarization of 63.9% and 61.1% respectively, which is far higher than the bulk n-MnSb spin polarization of approximately 18%. These interfaces become less energetically unfavourable than in the bulk n-MnSb, while the other possible atomic terminations at the interface are more unfavourable. In the case of the models of Sb(0001)/n-MnSb(0001) interfaces designed. The Sb layer prevents oxidation of the MnSb surface and the Mn-to-Sb termination of these epitaxial models shows that Sb can grow on MnSb with interesting properties, which agrees with ongoing experimental results. Ionic-covalent bond mix is observed on the Mn-to-Sb termination of the Sb(0001)/n-MnSb(0001) interface, which have a reverse spin polarization of -57.7%. At the low index interfaces NiO(111)/MgO(111), NiO(001)/MgO(001) and NiO(110)/MgO(110) a half-metallic ferrimagnetic behaviour is seen on the Ni-to-O termination of the NiO(001)/ MgO(001) interface. Whereas the energetically more favourable Ni-to-O termination of the NiO(111)/ MgO(111) interface structure display a half-metallic like property at its interface. The main aim of this study is to find new interfacial systems with highly spin polarized interface, which may be used for an efficient spin injection device and spin polarization calculation have revealed such interfaces.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.731351  DOI: Not available
Keywords: QC Physics
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