The production of metal objects in industry largely depends on cutting operations such as turning, milling, and drilling. Such operations use cutting tools with replaceable inserts made of cemented carbide, designed with precise geometry and material properties. To enhance the longevity of the inserts, they are typically coated with a thin layer (a few micrometers) of a hard, wear-resistant material. This use of wear-resistant protective coatings represents one of the most promising strategies for enhancing the functional properties of contact materials, thereby effectively addressing issues related to friction and wear. Multicomponent coatings formulated from e.g., cubic aluminium titanium nitride (c-Al_xTi_1-xN) solid solutions are recognized for their exceptional hardness, along with thermal stability and resistance to wear and oxidation. These coatings can be applied onto the cutting inserts through deposition methods such as chemical vapor deposition (CVD).

The aim of this thesis is to establish a foundation and extend the understanding of the surface chemistry during the deposition of Al_xTi_1-xN by CVD. Research in recent years has demonstrated that metastable c-Al_xTi_1-xN with high aluminium content can be deposited near thermodynamic equilibrium using CVD techniques at very low pressures. However, the underlying CVD chemistry of these processes remains poorly understood, which limits the development of these processes to speculative approaches rather than scientifically grounded strategies. Because the CVD of Al_xTi_1-xN is not yet fully understood, atomic layer deposition (ALD) — a time-resolved variant of CVD — can serve as a valuable model system for investigating its surface chemistry and underlying reaction mechanisms. ALD enables a stepwise, temporally separated approach to studying these complex surface processes. By dividing the ternary Al_xTi_1-xN into its constituent binary components (TiN and AlN) and examining each one individually before combining them into the ternary material, we can systematically unravel the surface reactions involved. This time-resolved strategy provides a more controlled and detailed pathway to understanding the overall CVD process.

Reaction mechanism studies focus on understanding how and why a thin film forms. The identification of the chemical reactions that occur during each precursor pulse allows researchers to connect the dots that lead to the overall growth process. The findings in this thesis give a basis for a comprehensive understanding of the deposition chemistry at the atomic scale using different techniques to study surface chemistry, thereby enabling the advancement of more efficient and sustainable Al_xTi_1-xN CVD processes. This was conducted by utilization of different precursors: trimethyl aluminium (TMA, Al(CH₃)₃) and tris-dimethylamido aluminium (TDMAA, Al(NMe₂)₃) as the Al precursors and tetrakis-dimethylamido titanium (TDMAT, Ti(NMe₂)₄) as the Ti precursor, while NH₃ acted as the N source. Furthermore, established ALD methods for the binaries TiN and AlN were employed to create an alternative ALD approach for the ternary Al_xTi_1-xN deposition. In situ, operando and ex situ measurements were taken from these ALD processes and proved effective for studying surface reaction mechanisms, as they provided chemical information before, during and after the deposition process.