Triruthenium dodecarbonyl and trimethylphosphine or triphenylphosphine, and cis-ruthenium(II)dihydridotetrakis-(trimethylphophine) were used in flowing hydrogen or argon at 575 K to explore the effect of changing the percentage of P on the amorphous character of the films and on the electrical properties of the films. First-principles density-functional calculations are presented that reveal the interaction of Ru with P, and that predict the amorphous structure should be most stable above 20 at.% P and 10 at.% B. The films contained a carbon impurity that depended on the delivery gas and the alkylphoshphine source; film resistivity was highly dependent on the carbon impurity level. The microstructure changed with the percentage P; amorphous films formed provided the percentage of P exceeded 15 at.%. Film resistivity was most sensitive to the carbon impurity and also changed with microstructure. A 15 nm thick, amorphous film containing ∼15 at.% P had a resistivity of 210 μohm-cm.