Effect of the deposition temperature on the properties of Zn3N2 layers grown by rf magnetron sputtering

In this work, polycrystalline zinc nitride films were prepared on Si and glass substrates by rf magnetron sputtering in N₂ ambient using Zn as a target. Substrate temperature (T_s) was different for each deposition process ranging from 298 K to 523 K. Optical transmission experiments showed that the optical band gap of the resultant layers decreased as T_s increased. X-ray diffraction scans presented a pattern of oriented crystals along the (100) direction at low T_s in contrast to the highly disoriented patterns obtained at high T_s. Hall measurements were carried out and exhibited n-type character for all samples, with mobilities ranging between 10 and 30 cm²/Vs, and a resistivity reduction as substrate temperature increases. By scanning electron microscopy, it was possible to study the grain structure forming the surface of zinc nitride. The size of the grains became larger as T_s increased, which accounts for the reduction of the electrical resistivity.