The thermal decomposition of Ni3N thin films, deposited by chemical vapor deposition on SrTiO3 (001) and Si (100) substrates, has been studied by in situ x-ray diffraction, as well as temperature-programed controlled gas emission in both inert and hydrogen atmospheres. The decomposition at inert atmosphere conditions starts at the film/substrate interface, which results in a high degree of ordering in the formed nickel film. In the H-2 atmosphere, the initial film ordering is less pronounced and the decomposition occurs from the film surface and downward. This means that by choosing the annealing atmosphere, inert or hydrogen, the formation of the Ni film can be localized to either the original nitride/substrate interface or to the surface of the nitride. The annealed films show a cube-on-cube growth with respect to the SrTiO3 (001) substrate. The film morphology after the annealing experiments resembles the one of the as-deposited films. The lowest resistivity value is measured for the films annealed in the H-2 atmosphere. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3478298]