The thin film technology is of great importance in modern society and is a key technology in wide spread applications from electronics and solar cells to hard protective coatings on cutting tools and diffusion barriers in food packaging. This thesis deals with various aspects of thin film processing and the aim of the work is twofold; firstly, to obtain a fundamental understanding of the sputter deposition and the reactive sputter deposition processes, and secondly, to evaluate sputter deposition of specific material systems with low friction properties and to improve their performance.From studies of the reactive sputtering process, two new methods of eliminating the problematic and undesirable hysteresis effect were found. In the first method it was demonstrated that an increased process pressure caused a reduction and, in some cases, even elimination of the hysteresis. In the second method it was shown that sufficiently high oxide content in the target will eliminate the hysteresis. Further studies of non-reactive magnetron sputtering of multi-element targets at different pressures resulted in huge pressure dependent compositional gradients over the chamber due to different gas phase scattering of the elements. This has been qualitatively known for a long time but the results presented here now enable a quantitative estimation of such effects. For example, by taking gas phase scattering into consideration during sputtering from a WS2 target it was possible to deposit WSx films with a sulphur content going from sub-stoichiometric to over-stoichiometric composition depending on the substrate position relative the target. By alloying tungsten disulphide (WS2) with carbon and titanium (W-S-C-Ti) its hardness was significantly increased due to the formation of a new titanium carbide phase (TiCxSy). The best sample increased its hardness to 18 GPa (compared to 4 GPa for the corresponding W-S-C coating) while still maintaining a low friction (µ=0.02) due to the formation of easily sheared WS2 planes in the wear track.

The production of large area, high quality two-dimensional (2D) materials using chemical vapour deposition (CVD) has been an important and difficult topic in contemporary materials science research, after the discovery of the diverse and extraordinary properties exhibited by these materials. This thesis mainly focuses on the CVD synthesis of two 2D materials; bilayer graphene and monolayer tungsten disulphide (WS2). Various factors influencing the growth of each material were studied in order to understand how they affect the quality, uniformity, and size of the 2D films produced. Following this, these materials were combined to fabricate 2D vertical heterostructures, which were then spectroscopically examined and characterised. By conducting ambient pressure CVD growth with a flat support, it was found that high uniform bilayer graphene could be grown on the centimetre scale. The flat support provides for the consistent delivery of precursor to the copper catalyst for graphene growth. These results provide important insights not only into the upscaling of CVD methods for growing large area, high quality graphene and but also in how to transfer the product onto flexible substrates for potential applications as a transparent conducting electrode. Monolayer WS2 is of interest for use in optoelectronic devices due to its direct bandgap and high photoluminescence (PL) intensity. This thesis shows how the controlled addition of hydrogen into the CVD growth of WS2 can lead to separately distributed domains or centimetre scale continuous monolayer films at ambient pressure without the need for seed molecules, specially prepared substrates or low pressure vacuum systems. This CVD reaction is simple and efficient, ideal for mass-production of large area monolayer WS2. Subsequent studies showed that hexagonal domains of monolayer WS2 can have discrete segmentation in their PL emission intensity, forming symmetric patterns with alternating bright and dark regions. Analysis of the PL spectra shows differences in the exciton to trion ratio, indicating variations in the exciton recombination dynamics. These results provide important insights into the spatially varying properties of these CVD-grown TMDs materials, which may be important for their effective implementation in fast photo sensors and optical switches. Finally, by introducing a novel non-aqueous transfer method, it was possible to create vertical stacks of mixed 2D layers containing a strained monolayer of WS2, boron nitride, and graphene. Stronger interactions between WS2 on graphene was found when swapping water for IPA, likely resulting from reduced contamination between the layers associated with aqueous impurities. This transfer method is suitable for layer by layer control of 2D material vertical stacks and is shown to be possible for all CVD grown samples, a result which opens up pathways for the rapid large scale fabrication of vertical heterostructure systems with large area coverage and controllable thickness on the atomic level.

The use of low-friction coatings on machine elements is steadily increasing, and they are expected to play an important role in the reduction of fuel consumption of future motorized vehicles. Many low-friction coatings function by transformation of the outermost coating layer into tribofilms, which then cover the coating surface and its counter surface. It is within these tribofilms that sliding takes place, and their properties largely determine the performance. The role of the coating is then not to provide low friction, but to supply support and constituents for the tribofilm. In this thesis, the formation of such tribofilms has been studied for a number of different low-friction coatings. The sensitivity of the tribofilm formation towards changes in the tribological system, such as increased surface roughness, varied surrounding atmosphere and reduced availability of the tribofilm constituents has been given special attention. For TaC/aC coatings, the formation of a functioning tribofilm was found to be a multi-step process, where wear fragments are formed, agglomerated, compacted and eventually stabilized into a dense film of fine grains. This formation is delayed by a moderate roughening of the coated surface. Coatings based on tungsten disulphide (WS2) are often able to provide exceptionally low friction, but their use is restricted by their poor mechanical properties and sensitivity to humidity. Large improvements in the mechanical properties can be achieved by addition of for example carbon, but the achievable hardness is still limited. When titanium was added to W-S-C coatings, a carbidic hard phase was formed, causing drastically increased hardness, with retained low friction. Titanium oxides in the tribofilms however caused the friction to be high initially and unstable in the long term. In a study of W-S-N coatings, the effects of humidity and oxygen were studied separately, and it was found that the detrimental role of oxygen is larger than often assumed. Low friction tribofilms may form by rearrangement of coating material, but also by tribochemical reactions between constituents of the coating and its counter surface. This was observed for Ti-C-S coatings, which formed WS2 tribofilms when sliding against tungsten counter surfaces, leading to dramatic friction reductions.