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Controlled synthesis of tellurium nanowires by physical vapor deposition
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0003-4368-0651
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-1314-5407
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2022 (English)In: Nanomaterials, E-ISSN 2079-4991, Vol. 12, no 23, article id 4137Article in journal (Refereed) Published
Abstract [en]

One-dimensional tellurium nanostructures can exhibit distinct electronic properties from those seen in bulk Te. The electronic properties of nanostructured Te are highly dependent on their morphology, and thus controlled synthesis processes are required. Here, highly crystalline tellurium nanowires were produced via physical vapour deposition. We used growth temperature, heating rate, flow of the carrier gas, and growth time to control the degree of supersaturation in the region where Te nanostructures are grown. The latter leads to a control in the nucleation and morphology of Te nanostructures. We observed that Te nanowires grow via the vapour–solid mechanism where a Te particle acts as a seed. Transmission electron microscopy (TEM) and electron diffraction studies revealed that Te nanowires have a trigonal crystal structure and grow along the (0001) direction. Their diameter can be tuned from 26 to 200 nm with lengths from 8.5 to 22 μm, where the highest aspect ratio of 327 was obtained for wires measuring 26 nm in diameter and 8.5 μm in length. We investigated the use of bismuth as an additive to reduce the formation of tellurium oxides, and we discuss the effect of other growth parameters.

Place, publisher, year, edition, pages
MDPI, 2022. Vol. 12, no 23, article id 4137
Keywords [en]
tellurium, bismuth, doping, nanowires, physical vapour deposition
National Category
Other Physics Topics
Identifiers
URN: urn:nbn:se:umu:diva-200957DOI: 10.3390/nano12234137ISI: 000896197300001PubMedID: 36500758Scopus ID: 2-s2.0-85143740574OAI: oai:DiVA.org:umu-200957DiVA, id: diva2:1710227
Note

Originally included in thesis in manuscript form. 

Available from: 2022-11-11 Created: 2022-11-11 Last updated: 2023-01-17Bibliographically approved
In thesis
1. Surface analysis of low dimensional materials: revealing their electronic properties by advanced spectroscopy
Open this publication in new window or tab >>Surface analysis of low dimensional materials: revealing their electronic properties by advanced spectroscopy
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Ytanalys av låg-dimensionella material : studier av elektroniska egenskaper med avancerad spektroskopi
Abstract [en]

Low-dimensional materials (0D, 1D, 2D) have been widely used to develop modern miniaturized (micro- and nano-) technology. The use of these materials come from their extraordinary optical, electrical, thermal, and mechanical properties, which are very different from the bulk crystal. To understand low-dimensional materials there is a large interest in studying the surface states of such materials, because the topmost few atomic layers possess an atomic arrangement and electronic structure different from the crystal bulk and hence responsible for many of the novel properties. 

In surface science, the techniques typically probe the topmost 1-10 nm of surfaces exposed to vacuum. X-ray photoemission spectroscopy (XPS) is the most common surface technique used because of its relatively easy handling and good ability to reveal important information on the surface oxidation states. XPS involves radiation of light that penetrates a sample up to 10 nm depth. Ultraviolet photoemission spectroscopy (UPS) is another surface-sensitive technique, with a slightly lower probing depth, on average about 2.5 nm. 

For the research in this thesis, a vacuum system has been constructed that contains surface analytical equipment for UPS, Angle Resolved Photospectroscopy and Low-electron energy diffraction. Normally, XPS and UPS are used as individual techniques as they both determine different properties of the material. However, hereby for many applications both are used in conjunction because they complement each other and provide a comprehensive analysis of the samples structure and electronic properties.

The aim of this thesis is to present surface analytical measurements carried on low-dimensional materials. Among the materials studied is Graphene, used to as a proof-of-principle experiment in the vacuum system constructed as it has been extensively studied and information can be easily found. The second material was Cu2O thin films that shows different chemical and electronic properties depending on the oxidation level. The third material is nanoporous GaN that exhibit V-pits that modify the properties of the material depending on the hole sizes. The fourth material are trigonal Te nanowires, 1D nanostructures that has a narrow direct bandgap, a high-hole mobility, and a high current density. Finally, an application of the constructed setup is show characterizing the electronic properties of NiFeMo solids. 

Abstract [sv]

Lågdimensionella material (0D, 1D, 2D) har använts i stor utsträckning för att utveckla modern miniatyriserad (mikro- och nano-) teknologi. Användningen av dessa material kommer från deras extraordinära optiska, elektriska, termiska och mekaniska egenskaper, som skiljer sig mycket från bulkkristallen. För att förstå lågdimensionella material finns det ett stort intresse av att studera deras yttillstånd, detta eftersom de översta atomskikten har en atom- och elektronstruktur som skiljer sig från kristallen i stort och således har stor inverkan för många av de egenskaperna.

Inom ytvetenskap undersöker man med de vanligaste teknikerna normalt de översta 1-10 nm av ytor exponerade i vakuum. Röntgenfotoemissionsspektroskopi (XPS) är den vanligaste yttekniken. Den används på grund av dess relativt enkla hantering och goda förmåga att ge viktig information om ytoxidationstillstånden. XPS involverar strålning av ljus som penetrerar ett prov upp till ett djup av 10 nm. Ultraviolett fotoemissionsspektroskopi (UPS) är en annan ytkänslig teknik, med ett något lägre sonderingsdjup, i genomsnitt cirka 2.5 nm. 

För forskningen i denna avhandling har ett vakuumsystem konstruerats som innehåller ytanalysutrustning för UPS, vinkelupplöst fotospektroskopi och lågelektron-energidiffraktion. Normalt används XPS och UPS som individuella tekniker eftersom de båda bestämmer olika egenskaper hos materialet. Men för många applikationer används båda i kombination eftersom de kompletterar varandra och ger en omfattande analys av provstrukturen och dess elektroniska egenskaper.

Syftet med denna avhandling är att presentera ytanalytiska mätningar utförda på lågdimensionella material. Bland de studerade materialen används grafen som ett experimentellt modellsystem för det konstruerade vakuumsystemet, detta eftersom det har studerats omfattande och information om materialet är lättillgänglig. Det andra materialet som studerades var tunna filmer av Cu2O som uppvisade olika kemiska- och elektroniska egenskaper beroende på oxidationsnivån. Det tredje materialet,  ett nanoporöst GaN med V-formade gropar som modifierar materialets egenskaper beroende på hålstorlek. Det fjärde materialet var trigonala Te nanotrådar, 1D nanostrukturer som har ett litet direkt bandgap, en hög hålrörlighet, och en hög strömtäthet. I den sista studien i avhandlingen studerades NiFeMo, ett material som tillämpas inom elektrokatalys. Uppställningen utnyttjades för att kunna korrelera vissa ytegenskaper hos materialet till de katalytiska egenskaperna för vätgasevolution. 

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2022. p. 88
Keywords
Low-dimensional materials, surface science, surface-sensitive techniques, angle-resolved photoemission spectroscopy, ultraviolet photoemission spectroscopy, electronic properties
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-200953 (URN)978-91-7855-944-2 (ISBN)978-91-7855-943-5 (ISBN)
Public defence
2022-12-06, NAT.D.320, Naturvetarhuset, Umeå, 10:15 (English)
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Available from: 2022-11-15 Created: 2022-11-11 Last updated: 2022-11-11Bibliographically approved

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Miranda la Hera, VladimirWu, XiuyuMena, JosuéBarzegar, Hamid RezaKoroidov, SergeyWågberg, ThomasGracia-Espino, Eduardo

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