Optoelectronic properties of Cu3N thin films deposited by reactive magnetron sputtering and its diode rectification characteristics

In this work, we discuss the effects of working pressure on the microstructures, electrical, and optical properties of Cu3N films. The working pressures were varied from 5 mtorr to 23 mtorr while gas flow ratio of N-2 to Ar was maintained. When the working pressure increases, the Cu3N (111) peak intensity decreases as evident from the XRD analysis. The films' conductivity type also varies from n-type to p-type with increasing working pressure. When working pressure is 15 mtorr, the resistivity is 1.575 Omega cm and the sample conduction becomes p-type. This is possibly due to the formation of many Cu vacancies (i.e. vacancies at Cu cation sites) in the films. When the working pressure is 5 mtorr, a Cu (111) peak was observed. It disappears upon increasing the working pressure. It was also found that the ratio of Cu2+/Cu(+ )increases from 0.39 to 0.93 when the working pressure is raised from 5 mtorr to 20 mtorr. A rise in substitution of Cu2+ for Cu+ results in the formation of more Cu vacancies, which leads to the transition in conduction from n-type to p-type. Finally, we fabricated p-type Cu3N/n-type Cu3N homojunction and p-type Cu3N/n-type ZnO heterojunction diodes. It was found that p-type Cu3N/n-type Cu3N homojunction devices do not show significant rectification effects. As we observed, at +/- 3 V, the I-on/I-off value was only below 1. Whereas, in p-type Cu3N/n-type ZnO heterojunction devices, a higher I-on/I(off )value of 3118 can be achieved. Heterojunction devices outperform the homojunction devices despite the interfacial issues, which we believe is due to the high value of the built-in potential (V-bi) of the p-n junctions. (C) 2019 Elsevier B.V. All rights reserved.