As semiconductor device dimensions approach their physical limits, the growth pace driven by Moore's Law has slowed, necessitating substantial advancements. Conventional top-down fabrication processes face increasing challenges, particularly as devices shrink to deep sub-10-nm dimensions. Atomic Layer Deposition (ALD) has emerged as a critical solution due to its advantages over traditional technologies, making it essential for continued miniaturization. This study focuses on two main objectives: first, employing Density Functional Theory (DFT) to understand co-reactant reactions during ALD, and second, identifying novel self-assembled monolayers (SAM)/co- adsorbates for area-selective ALD using a custom-built quartz crystal microbalance (QCM) reactor. In our initial study, building on prior research, we aimed to elucidate the reaction mechanisms in film formation using t-BuOH. Using ab-initio DFT calculations, we analyzed different reaction pathways and their energetics. We also examined other alcohols for similar behavior. The study concluded that carbocation stability significantly influences the formation of a stable film product. In our second study, we created a passivation layer using HDFTEOS vapor phase SAM to evaluate its blocking capacity against alumina deposition with an alternative aluminum precursor and water co-reactant. The results indicated that the SAM's blocking capacity was limited.