In this dissertation, key aspects of the surface chemistry associated with gas phase deposition and etching are discussed. Atomic layer deposition (ALD) is a gas-phase deposition technique primarily known for its superior self-limiting binary process that affords precise control, uniform and conformal thin film growth. Despite the extensive work done with ALD, the mechanisms behind nucleation and steady state growth remain unclear for many ALD processes. Additionally, in an effort to meet today's device integration requirements, e.g., scaling down nanostructures and thermal budget restrictions during film deposition, thermal ALD processes requiring high temperatures (>300 C) are now being forced out of production due to adverse thermally induced side effects, e.g., device degradation. To address this challenge and promote reactivity at low temperatures (