A successful thermal ALD process usually requires a thermodynamic driving force, i.e., being exergonic as shown by a negative Gibbs free reaction energy Δ𝐺 r (eq. 1.1) for all reaction steps. Exceptions are the growth of metastable materials and ALD processes using continuous energy input (e.g., plasma ALD). A + B → C , Δ𝐺 r < 0