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Abstract We studied CrN thin films grown by a reactive direct current magnetron sputtering process. Starting with pure Cr, as nitrogen is added, initially N atoms occupy interstitial positions in bcc Cr and when the amount of N increases an amorphous structure emerge. Subsequently, fcc chromium mononitride (CrN) phase start to appear and stoichiometric CrN get formed when the amount of reactive nitrogen gas is about one-third of argon gas. While, the long range ordering of CrN film seems to be stable up to 873 K, signatures of local instabilities can be seen in the N K-edge absorption pattern at lower temperatures. To improve the thermal stability of CrN films, we used oxygen (O) as a surfactant. We found that O works like a surfactant when used in a minuscule amount (0.25%). In the O surfactant mediated growth, O does not react with CrN film. An accumulation of O at the surface of CrN film can be seen in the O K-edge absorption pattern, typically expected in surfactant mediated growth. However, when the amount of O gas flow is increased from 0.25 to 0.5%, it no longer acts as a surfactant and severely affects both long and short range structure of CrN film as occurrence of Cr 2 O 3 phase can now be seen. Surfactant mediated CrN films clearly show denser and smoother films with superior thermal stability. Highlights • CrN thin films grown by reactive magnetron sputtering have been studied. • The mechanism for formation of stoichiometric CrN phase was obtained. • N K-edge absorption spectra reveals thermal instabilities in CrN films. • By using O as a surfactant, resulting CrN films are superior. • Thermal stability of CrN films improve when O is used as a surfactant. [ABSTRACT FROM AUTHOR]