Influence of the post-heat treatments on thermal stability of copper nitride deposited in Ar-free sputtering process

Copper nitride (Cu 3 N) is considered a very promising and relevant material in applications such as next-generation solar cells, energy storage, microelectronics, and/or optical data storage. This is thanks to its tunable optoelectronic properties, low toxicity, and high electrochemical activity. However, its metastable character, thermodynamically unstable at such relatively low temperatures (100-470 °C), could seriously limit its functionality. In this work, the thermal stability of the Cu 3 N is evaluated after subjecting the material to different post-heat treatments carried out changing the annealing atmospheres, air and vacuum, in a temperature range of 100 to 400 °C. The nitride thin films are fabricated by reactive radio-frequency magnetron sputtering in pure nitrogen at room temperature. After the annealing, the changes in the composition, structural and optoelectronic properties of Cu 3 N are determined. The results show the strong influence of the thermal treatment atmosphere on the film stability, establishing the minimum temperature at which the material begins to decompose. Under the post heat treatment in air, the material remains almost stable up to annealing temperatures close to 200 °C. In this case, important changes in the properties begin to be observed from the appearance of the bubbles on the surface. If the annealing is carried out in vacuum, the properties of the thin films remain practically stable up to 400 °C, significantly increasing its decomposition temperature limit. The results achieve so far clearly open the possibility to noticeably improve the optoelectronic properties and the stability of the Cu 3 N up to temperatures of 400 °C, without compromising its integrity, which would greatly favor its application.