20.500.12556/RUL-121517 Electrical, optical and structural properties of low-dimensional materials based on tungsten Električne, optične in strukturne lastnosti nizko-dimenzionalnih materialov na osnovi volframa Substoichiometric tungsten oxides are an interesting class of materials, where defects form periodic structures. These defects are called crystallographic shear (CS) planes and depending on the type of the CS plane and the distance between them, they can form tungsten suboxides with different stoichiometries. In this Thesis quasi-two-dimensional substoichiometric tungsten oxide structures, which nucleate by epitaxial growth on the W$_{19}$O$_{55}$ nanowires and grow as thin platelets, were identified. Both the nanowires and the platelets accommodate oxygen deficiency by formation of crystallographic shear planes. High resolution electron microscopy, x-ray photoelectron spectroscopy and x-ray diffraction were used for structural determination, Raman spectroscopy for vibrational analysis, and optical absorption, Kelvin microscopy and scanning tunnelling spectroscopy for elucidation of electric properties. The used experimental techniques are discussed in the Methods chapter, in the Publication overview chapter an overview of the literature is presented and in the Results and discussion chapter the results are presented and discussed. Stoichiometric phases, W$_{18}$O$_{53}$ (WO$_{2.944}$), W$_{17}$O$_{50}$ (WO$_{2.941}$), W$_{16}$O$_{47}$ (WO$_{2.938}$), W$_{15}$O$_{44}$ (WO$_{2.933}$), W$_{14}$O$_{41}$ (WO$_{2.929}$), W$_{9}$O$_{26}$ (WO$_{2.889}$), and W$_{10}$O$_{29}$ (WO$_{2.9}$), syntactically grow inside a single platelet. Six of the seven identified phases were observed for the first time which were predicted more than 70 years ago. These platelet-like crystals represent a new kind of polycrystallinity, where crystallographic shear planes accommodate oxygen deficiency and at the same time stabilize this multi-stoichiometric structure. Podstehiometrični volframovi oksidi predstavljajo zanimivo vrsto materialov, kjer se defekti uredijo v periodične strukture. Omenjenim periodičnim strukturam pravimo kristalografske strižne ravnine. Glede na tip kristalografske strižne ravnine in razdalje med njimi, te lahko tvorijo volframove okside z različnimi stehiometrijami. V sklopu disertacije so bili identificirani kvazi dvodimenzionalni podstehiometrični volframovi oksidi, ki epitaksialno rastejo na nanožicah W$_{19}$O$_{55}$ kot tanke ploščice. Tako nanožice kot ploščice odpravljajo pomanjkanje kisika s tvorbo kristalografskih strižnih ravnin. Transmisijska elektronska mikroskopija, rentgenska fotoelektronska spektroskopija in rentgenska praškovna difrakcija so bile uporabljene za določitev strukture, Ramanska spektroskopija za analizo nihajnih načinov snovi, UV-Vis spektroskopija, Kelvinova tipalna mikroskopija in vrstična tunelska mikroskopija za določitev električnih lastnosti. Uporabljene metode so predstavljene v poglavju Metode. V poglavju Publikacije so predstavljena zadnja dognanja v literaturi glede omenjenih materialov, v poglavju Rezultati in diskusija pa so predstavljeni rezultati skupaj z diskusijo. Stehiometrične faze, W$_{18}$O$_{53}$ (WO$_{2.944}$), W$_{17}$O$_{50}$ (WO$_{2.941}$), W$_{16}$O$_{47}$ (WO$_{2.938}$), W$_{15}$O$_{44}$ (WO$_{2.933}$), W$_{14}$O$_{41}$ (WO$_{2.929}$), W$_{9}$O$_{26}$ (WO$_{2.889}$) in W$_{10}$O$_{29}$ (WO$_{2.9}$) sintaktično rastejo znotraj ene same ploščice. Šest od sedmih stehiometrij je bilo prvič eksperimentalno opaženih, čeprav so bile predvidene že pred skoraj 70 leti. Ploščicam podobni kristali predstavljajo novo vrsto polikristaliničnosti, kjer kristalografske strižne ravnine odpravljajo pomanjkanje kisika in hkrati stabilizirajo to več stehiometrično strukturo. tungsten sub-oxides nanomaterials characterization multi- stoichiometric single crystal volframovi oksidi nanomateriali karakterizacija multi-stehiometrični kristali true false false Angleški jezik Slovenski jezik Doktorsko delo/naloga 2020-10-13 11:47:39 2020-10-13 11:47:43 2022-09-02 03:59:44 0000-00-00 00:00:00 2020 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 113408 31357955 1523.pdf 1523.pdf 1 0CFFA477608EFE2AF251E419905D3DE1 31c8e872490da4554dab9b404b77f7d2c2a2a6de9ceb2f43b1ecc33534060f23 e72bcaa6-a1ba-11eb-a523-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=136452 Fakulteta za matematiko in fiziko 0 0 0