Med växande arealer som inte röjs, samt ett ökat intresse för skogsbränsleuttag, krävs utveckling av teknik och metoder för att kunna utvinna denna resurs. Genom att, från uppställningsplatser i stickväg, avverka träd i krankorridorer minskar antalet kranrörelser per träd. Detta minskar i sin tur den höga avverkningskostnaden i stamtäta, klena bestånd. I ett tallbestånd i södra Sverige undersöktes metoden krankorridorgallring. I transekter vinkelrätt från stickväg mättes höjd, brösthöjdsdiameter, stubbdiameter, stamantal, trädslagsblandning, stubbhöjder och skador, samt dess stickvägsavstånd. Detta beräknades sedan i Excel. Gallringskvoten var på 0,77, alltså ökade beståndets medeldiameter och höjd. Gallringsstyrkan låg på 53% med 61% avverkade träd i krankorridorer, resten i stickväg. Andelen skador var 1.5% och stubbhöjden 48 cm, inga av dessa kunde korreleras till stickvägsavståndet. Innan åtgärd stod endast 2267 stammar >3cm per hektar, bestånd med högre stamantal behövs för en bättre utvärdering av metoden. / With a growing number of unmanaged stands with a high number of stems per hectare and low diameters, and with growing interests in biomass extractions for fuel, development of proper technology and methods to extract these resources is required. By mechanical harvesting of trees in corridors, the number of crane movements per tree is decreased, resulting in lower harvest costs. In a pine stand in southern Sweden, this method of boom-corridor thinning was examined. This was done by measuring, perpendicular to the strip road, mean heights, breast height- and stump diameters, number of stems, tree species composition, stump heights and damages from thinning and later calculated in Excel. The relationship between harvested and standing tree diameters where 0,77, which can be compared to a heavy thinning from below. The thinning grade resulted in 53% with 61% trees harvested in boom-corridors. Damage percent resulted in 1.5% and the mean stump-height was 48 cm, none of these factors could be connected to their strip-road distance. Before thinning the number of stems was 2267 stems >3cm per hectare. For a better evaluation of the method, stands with higher number of stems would be required.

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.