Phase transition behavior of reactive sputtering deposited Co–N thin films using transmission electron microscopy

Cobalt nitride thin films could be prepared by employing a direct current reactive sputtering deposition on (100) silicon substrates in mixtures of fixed Ar (4×10 −1 Pa ) and N 2 at various partial pressures. The Co x N thin films could be tailored by appropriately controlling the partial pressure of the reactive nitrogen. With adequately increasing nitrogen to argon partial pressure, a series of sequence phase formation from α-Co, Co 4 N , Co 3 N , Co 2 N , and CoN could be observed. The phase transition sequence was accompanied by a substantial refinement and improvement of the films’ grain structure. Rapid thermal annealing of cobalt nitride thin films exhibited a stepwise decomposition via the dissociating of Co 4 N → Co 3 N +β- Co(N ), Co 3 N → Co 2 N +β- Co(N ), and Co 2 N → CoN +β- Co(N ) with increasing the elevated temperature. Phase formation, thermal decomposition, electrical resistivity, and microstructure of reactive sputtered cobalt nitride films were discussed in this study.