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Preparation and characterisation of optical and optoelectronic devices based in two-dimensional semiconductors

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Preparation and characterisation of optical and optoelectronic devices based in two-dimensional semiconductors

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dc.contributor.advisor	Sánchez Royo, Juan Francisco
dc.contributor.author	Andrés Penares, Daniel
dc.contributor.other	Departament de Física Aplicada i Electromagnetisme	es_ES
dc.date.accessioned	2020-01-21T08:21:53Z
dc.date.available	2021-01-21T05:45:04Z
dc.date.issued	2020	es_ES
dc.date.submitted	31-01-2020	es_ES
dc.identifier.uri	https://hdl.handle.net/10550/72665
dc.description.abstract	In the Materials Science field, two-dimensional materials have gained the scientific community attention in recent years. The change and the appearance of novel properties when their thickness is reduced to nanometric scale has special interest for its fundamental properties study for, from this base, the design and its implementation in devices. The wide variety of materials with the possibility of being exfoliated at the two-dimensional level opens the field to different applications, from optoelectronic devices, detection and sensing, energy storage, catalysis, medical applications and quantum information technologies, among others. This thesis gathers results in both directions: a fundamental science level study in two-dimensional materials less explored by the scientific community and its implementation in optoelectronic devices focused on different applications. In a first part, optical and electrical properties of III-VI semiconductors are studied. Photoluminescence (PL) of Gallium Selenide when thickness is reduced as well as its oxidation mechanism are discussed before its implementation. After this, electrical properties of 2D Indium Selenide (InSe) will be the focus of the study. This thesis demonstrates the usage of multiterraced nanosheets as p-n heterojunctions without joint defects. In addition, the thickness - work function dependence is studied by means of Kelvin-probe force microscopy. Finally, its usage for gas sensing due to the PL change in 2D samples is proposed and demonstrated. After its presentation, a second part of the thesis will focus on its implementation to take advantage of or to optimise the previous properties, comparing the results with monolayers of transition metal dichalcogenides (TMD) such as Tungsten Selenide or Molybdenum Selenide. Specifically, the recently demonstrated out-of-plane dipolar nature of the InSe nanosheets, which hampers its usual vertical excitation-collection performance, will be discussed. First, using silicon oxide microspheres on the 2D nanosheets, the PL collection will be enhanced. The behavior as an out-of-plane dipole will be demonstrated in 2D InSe and the low energy contribution of TMD PL emission due to the whispering gallery modes that occur in the microspheres. After this, these 2D materials will be studied in vertical heterostructures with perovskite nanocrystals, obtaining an enhancement in the PL collected in InSe nanosheets compared to that obtained with TMD, where PL detected is reduced by depositing a nanocrystalline perovskite on top, due to the orientation between perovskites emission and 2D dipolar natures. Closing this part, InSe nanosheets and TMD monolayers on photonic waveguides are studied, allowing excitation and collection in both horizontal and vertical directions. In a third and final part of the thesis two two-dimensional materials not explored in the literature will be presented: Bismuth Sulfide and Molybdenum Oxide. In the case of Bismuth Sulfide, a semiconductor material is presented that, in addition to its anisotropy between the exfoliation plane and the vertical direction, presents an unusual optical and structural anisotropy within the plane, demonstrated by several optical techniques such as Raman spectroscopy, photoluminescence, optical contrast, differential reflectivity and transmittance. The application of such anisotropy in optical fibers as a Fabry-Perot cavity in its core is demonstrated, from which results its birefringence is obtained in comparison with other reported laminar materials. Finally, Molybdenum Oxide is presented as a two-dimensional insulating material, uncommon in the two-dimensional materials field, where hexagonal Boron Nitride is the only one considered. The exfoliability of Molybdenum Oxide and its advantages over hexagonal Boron Nitride are demonstrated: its absence of low temperature defects and its almost-zero nuclear spin compared to hexagonal Boron Nitride, which hampers its usage in nuclear spintronics oriented devices. The usage of this new material as a two-dimensional insulator is demonstrated by the encapsulation of transition metal dichalcogenides monolayers within this material and studying its behavior at low temperature, from its single photon emitters behavior to the narrowing in the emission and absorption of the encapsulated semiconductor, obtained by photoluminescence and differential reflectivity at low temperature, respectively.	en_US
dc.description.abstract	In the Materials Science field, two-dimensional materials have gained the scientific community attention in recent years. The change and the appearance of novel properties when their thickness is reduced to nanometric scale has special interest for its fundamental properties study for, from this base, the design and its implementation in devices. The wide variety of materials with the possibility of being exfoliated at the two-dimensional level opens the field to different applications, from optoelectronic devices, detection and sensing, energy storage, catalysis, medical applications and quantum information technologies, among others. This thesis gathers results in both directions: a fundamental science level study in two-dimensional materials less explored by the scientific community and its implementation in optoelectronic devices focused on different applications. In a first part, optical and electrical properties of III-VI semiconductors are studied. Photoluminescence (PL) of Gallium Selenide when thickness is reduced as well as its oxidation mechanism are discussed before its implementation. After this, electrical properties of 2D Indium Selenide (InSe) will be the focus of the study. This thesis demonstrates the usage of multiterraced nanosheets as p-n heterojunctions without joint defects. In addition, the thickness - work function dependence is studied by means of Kelvin-probe force microscopy. Finally, its usage for gas sensing due to the PL change in 2D samples is proposed and demonstrated. After its presentation, a second part of the thesis will focus on its implementation to take advantage of or to optimise the previous properties, comparing the results with monolayers of transition metal dichalcogenides (TMD) such as Tungsten Selenide or Molybdenum Selenide. Specifically, the recently demonstrated out-of-plane dipolar nature of the InSe nanosheets, which hampers its usual vertical excitation-collection performance, will be discussed. First, using silicon oxide microspheres on the 2D nanosheets, the PL collection will be enhanced. The behavior as an out-of-plane dipole will be demonstrated in 2D InSe and the low energy contribution of TMD PL emission due to the whispering gallery modes that occur in the microspheres. After this, these 2D materials will be studied in vertical heterostructures with perovskite nanocrystals, obtaining an enhancement in the PL collected in InSe nanosheets compared to that obtained with TMD, where PL detected is reduced by depositing a nanocrystalline perovskite on top, due to the orientation between perovskites emission and 2D dipolar natures. Closing this part, InSe nanosheets and TMD monolayers on photonic waveguides are studied, allowing excitation and collection in both horizontal and vertical directions. In a third and final part of the thesis two two-dimensional materials not explored in the literature will be presented: Bismuth Sulfide and Molybdenum Oxide. In the case of Bismuth Sulfide, a semiconductor material is presented that, in addition to its anisotropy between the exfoliation plane and the vertical direction, presents an unusual optical and structural anisotropy within the plane, demonstrated by several optical techniques such as Raman spectroscopy, photoluminescence, optical contrast, differential reflectivity and transmittance. The application of such anisotropy in optical fibers as a Fabry-Perot cavity in its core is demonstrated, from which results its birefringence is obtained in comparison with other reported laminar materials. Finally, Molybdenum Oxide is presented as a two-dimensional insulating material, uncommon in the two-dimensional materials field, where hexagonal Boron Nitride is the only one considered. The exfoliability of Molybdenum Oxide and its advantages over hexagonal Boron Nitride are demonstrated: its absence of low temperature defects and its almost-zero nuclear spin compared to hexagonal Boron Nitride, which hampers its usage in nuclear spintronics oriented devices. The usage of this new material as a two-dimensional insulator is demonstrated by the encapsulation of transition metal dichalcogenides monolayers within this material and studying its behavior at low temperature, from its single photon emitters behavior to the narrowing in the emission and absorption of the encapsulated semiconductor, obtained by photoluminescence and differential reflectivity at low temperature, respectively.	es_ES
dc.format.extent	228 p.	es_ES
dc.language.iso	en	es_ES
dc.subject	two-dimensional semiconductors	es_ES
dc.subject	materiales bidimensionales	es_ES
dc.subject	nanomaterials	es_ES
dc.subject	nanomateriales	es_ES
dc.subject	gase	es_ES
dc.subject	inse	es_ES
dc.subject	wse2	es_ES
dc.subject	mose2	es_ES
dc.subject	bi2s3	es_ES
dc.subject	moo3	es_ES
dc.subject	optoelectronic devices	es_ES
dc.subject	dispositivos optoelectrónicos	es_ES
dc.subject	microspherical resonators	es_ES
dc.subject	resonadores microesféricos	es_ES
dc.subject	perovskites	es_ES
dc.subject	perovskitas	es_ES
dc.subject	waveguides	es_ES
dc.subject	guías de onda	es_ES
dc.subject	spectroscopy	es_ES
dc.subject	espectroscopía	es_ES
dc.title	Preparation and characterisation of optical and optoelectronic devices based in two-dimensional semiconductors	es_ES
dc.type	doctoral thesis	es_ES
dc.subject.unesco	UNESCO::FÍSICA::Física del estado sólido ::Dispositivos de estado sólido	es_ES
dc.embargo.terms	1 year	es_ES