3.10 Facultad de Física

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Browsing 3.10 Facultad de Física by Subject "530.141"

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    Propiedades magnéticas en sistemas bidimensionales : efecto de defectos magnéticos sustitucionales
    (2022) Arias Camacho, Isabel María; Mejía López, José Félix; Pontificia Universidad Católica de Chile. Facultad de Física
    In recent years, two-dimensional materials have attracted a great deal of attention due to their completely different properties compared to conventional three-dimensional materials. The search for a two-dimensional material that simultaneously fulfills certain properties such as a suitable gap, high in-plane carrier mobility or good environmental stability is the focus of much current research for use in spintronics or optoelectronics, to name but a few applications. If magnetism can also be introduced into them, their range of usefulness is considerably extended. This thesis offers a detailed study of the electronic and structural properties of different types of Bi2O2Se monolayers, using DFT calculations, and after doping them with transition metal impurities (Mn, Fe, Co and Ni) which will introduce magnetism into the system from their unpaired d electrons. This material is interesting because it simultaneously satisfies many of the desired properties, and also provides the possibility of being fabricated in a quasi-two-dimensional form, thanks to the alternation of the Bi2O2 and Se layers, joined by electrostatic interactions. Throughout this work we will see how the original monolayer is very sensitive to the introduction of "extra" carriers, changing easily from a semiconducting to a conducting character, how the passivation of the monolayer with hydrogen atoms is able to "stop" the electronic transfer between Bi and Se, thus maintaining the semiconducting identity of the three-dimensional material, although it is a model that does not adequately reproduce the experimental work, and the appearance of a reconstruction of the monolayer with identical stoichiometry to the initial one, but with very different properties. The introduction of the dopant will add additional magnetic properties, showing how the impurity is able to polarize the Se atoms of the surrounding planes and the appearance of low dispersion bands caused by the d orbitals which, in turn, could imply interesting phenomena for possible applications. In addition, this action also has consequences on the electronic properties of the material, producing a change in the valence of certain Bi atoms that will lead to the break of symmetry along the plane perpendicular to the monolayer. Finally, the study of other monolayer models which have the disadvantage of breaking the symmetry with respect to the Se planes, but which reproduce the desired electronic properties more adequately, is covered. In this way, this thesis tries to offer a detailed description of the advantages and disadvantages of each of the models seen from different electronic, structural and magnetic perspectives.