Paramagnetic centers were studied in different SiOx:N,H films deposited by plasma-enhanced chemical vapor deposition in a wide composition range. The total dangling-bond concentration is detected to be proportional to the oxygen content. Moreover, sample irradiation by ultraviolet light revealed also that nitrogen impurities play some role. In particular, the presence of N–H bonds induces a release of the film stress, which seems to be related to the concentration of dangling bonds. It is also shown that both weak Si–Si and Si–H bonds may serve as precursors for the dangling-bond formation. © 1999 American Vacuum Society.