Methods for passivating exposed surfaces within an apparatus for depositing thin films on a substrate are disclosed. Interior surfaces of a deposition chamber and conduits in communication therewith are passivated to prevent reactants used in a deposition process and reaction products from adsorbing or chemisorbing to the interior surfaces. The surfaces may be passivated for this purpose by surface treatments, lining, temperature regulation, or combinations thereof. A method for determining a temperature or temperature range at which to maintain a surface to minimize accumulation of reactants and reaction products is also disclosed. A deposition apparatus with passivated surfaces within the deposition chamber and gas flow paths is also disclosed.