Provided herein are methods and apparatus for deposition of pure metal films. The methods involve the use of oxygen-containing precursors. The metals include molybdenum (Mo) and tungsten (W). To deposit pure films with no more than one atomic percentage oxygen, the reducing agent to metal precursor ratio is significantly greater than 1. Molar ratios of 100:1 to 10000:1 may be used in some embodiments.