Elektrochemické metody nacházejí využití v mnoha aplikacích (např. senzorice, skladování el. energie nebo katalýze). Jejich nespornou výhodou je nízká finanční náročnost na přístrojové vybavení. Abychom lépe porozuměli procesům probíhajícím na elektrodách, je dobré znát elektronickou pásovou strukturu materiálu elektrody. Úkolem této práce je vyhodnotit výstupní práci a pozici hrany valenčního pásu nových materiálů pro elektrody, konkrétně cínem dopovaného oxidu india pokrytého nanotrubicemi sulfidu wolframičitého. Ultrafialová fotoelektronová spektroskopie a Kelvinova silová mikroskopie jsou metody použité pro tuto analýzu. Zvláštní důraz je kladen na přípravu vzorků elektrod pro měření, aby nedošlo k nesprávné interpretaci výsledků vlivem vnějších efektů jako je např. kontaminace nebo modifikace povrchu.

This thesis describes the fabrication and characterization of two-dimensional transition dichalcogenides (2D TMDs) nanolayers for various applications in electronic and opto-electronic devices applications. In Chapter 1, crystal and optical structure of TMDs materials are introduced. Many TMDs materials reveal three structure polytypes (1T, 2H, and 3R). The important electronic properties are determined by the crystal structure of TMDs; thus, the information of crystal structure is explained. In addition, the detailed information of photon vibration and optical band gap structure from single-layer to bulk TMDs materials are introduced in this chapter. In Chapter 2, detailed information of physical properties and synthesis techniques for molybdenum disulfide (MoS2), tungsten disulfide (WS2), and molybdenum ditelluride (MoTe2) nanolayers are explained. The three representative crystal structures are trigonal prismatic (hexagonal, H), octahedral (tetragonal, T), and distorted structure (Tʹ). At room temperature, the stable structure of MoS2 and WS2 is semiconducting 2H phase, and MoTe2 can reveal both 2H (semiconducting phase) and 1Tʹ (semi-metallic phase) phases determined by the existence of strains. In addition, the pros and cons of the synthesis techniques for nanolayers are discussed. In Chapter 3, the topic of synthesized large-scale MoS2, WS2, and MoTe2 films is considered. For MoS2 and WS2 films, the layer thickness is modulated from single-layer to multi-layers. The few-layer MoTe2 film is synthesized with two different phases (2H or 1Tʹ). The all TMDs films are fabricated using two-step chemical vapor deposition (CVD) method. The analyses of atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and Raman spectroscopy confirm that the synthesis of high crystalline MoS2, WS2, and MoTe2 films are successful. The electronic properties of both MoS2 and WS2 exhibit a p-type conduction with relatively high field effect mobility and current on/off ratio. In Chapter 4, vertically-stacked few-layer MoS2/WS2 heterostructures on SiO2/Si and flexible polyethylene terephthalate (PET) substrates is presented. Detailed structural characterizations by Raman spectroscopy and high-resolution/scanning transmission electron microscopy (HRTEM/STEM) show the structural integrity of two distinct 2D TMD layers with atomically sharp van der Waals (vdW) heterointerfaces. Electrical transport measurements of the MoS2/WS2 heterostructure reveal diode-like behavior with current on/off ratio of ~ 104. In Chapter 5, optically uniform and scalable single-layer Mo1-xWxS2 alloys are synthesized by a two-step CVD method followed by a laser thinning. Post laser treatment is presented for etching of few-layer Mo1-xWxS2 alloys down to single-layer alloys. The optical band gap is controlled from 1.871 to 1.971 eV with the variation in the tungsten (W) content, x = 0 to 1. PL and Raman mapping analyses confirm that the laser-thinning of the Mo1-xWxS2 alloys is a self-limiting process caused via heat dissipation to SiO2/Si substrate, resulting in fabrication of spatially uniform single-layer Mo1-xWxS2 alloy films.

This thesis aims to investigate the coefficient of friction between steel on steel contacts with the addition of solid lubricants such as h-BN, WS2, MoS2 in powder form, in dry conditions and wet conditions. More specifically, the purpose is to enhance the sliding between the piston rings and cylinder block in a modern high temperature steam engine developed by RANOTOR. The friction test was carried out as a linear sliding test with determined loads and sliding speed. Hertzian contact theory was deployed to calculate contact pressure and shear stresses to make sure the contact was elastic, alternatively plastic. It was found that WS2 and  MoS2 lowered the coefficient of friction quite heavily in dry conditions, acting as a thin protective-lubricating film. h-BN performed rather poorly, increasing the coefficient of friction. In a water slurry, none of the powders managed to decrease the COF due to the particles not interacting with the surfaces.The solid lubricants tested should be further tested as coatings since they acted like it in dry conditions. / Denna rapport syftar till att undersöka friktionskoefficienten i stålkontakter med tillsats av fasta smörjmedel som  h-BN, WS2, MoS2 i pulverform, under torra och våta förhållanden. Mer specifikt är syftet att förbättra glidningen mellan kolvringarna och insidan av cylindern i en modern högtemperatur-ångmotor utvecklad av RANOTOR. Friktionstestet genomfördes som ett linjärt glidtest med bestämda belastningar och glidhastighet. Hertzian-kontaktteorin användes för att beräkna kontakttryck och skjuvspänningar för att säkerställa att kontakten var elastisk alternativt plastisk. Det visade sig att WS2och MoS2 kraftigt sänkte friktionskoefficienten under torra förhållanden genom att agera som en tunn skyddande-smörjfilm. h-BN presterade dåligt och ökade friktionskoefficienten. I vattenblandning lyckades inget av pulverna minska friktionskoefficienten eftersom partiklarna inte interagerade med ytorna. De testade fasta smörjmedlen bör vidare testas som beläggningar eftersom de fungerade som dessa under torra förhållanden.