Cupric oxide (CuO) is abundant, a nontoxic semiconductor with p-type conductivity, and the direct bandgap of around 1.4-1.5 eV at room temperature enables an energy conversion efficiency of more than 30 % in the case of the single-junction solar cell. Moreover, it has promising applications in batteries, biosensors, catalysis, energetic materials, field emissions, gas sensors, supercapacitors, nanofluid, photodetectors, and so on. To realize good quality optoelectronic devices, it is crucial to control the conductivity of the films, and nitrogen (N) is one of the possible dopants for CuO, which is expected to act as acceptor by replacing O lattice site. In this work, N-doped CuO thin films have been fabricated on α-Al2O3(0001) using a pure Cu target in an ambient of Ar, O2, and N2 plasma by radio frequency reactive magnetron sputtering. The physical properties of the N-doped and undoped CuO thin films were examined systematically with the variation of N2 gas flow rate. A strong impact of N-doping was identified on the composition as well as functional characteristics of the CuO films with the variation of N2 gas flow rate. Structural characterization by X-ray diffraction and Raman spectroscopy revealed the growth of the single phase of N-doped and undoped CuO at the studied range of N2 gas flow rate. All the CuO thin films demonstrated p-type conductivity. The resistivity of N-doped CuO was dropped sequentially from 810 to 18 Wcm, while the carrier density raised from 2.6×1017 to 7.7×1019 cm−3 with the increase of N2 gas flow rate. The activation energy of N-doped CuO was measured as 0.15 eV at 150∼370 K. Optical absorption results of both undoped and N-doped CuO films by UV-Vis spectroscopic method exhibited a direct transition at Eg=1.52~1.56 eV with a high absorption coefficient of &gt;104 cm-1. These outcomes illustrate the p-type conductivity control of CuO by N-doping, taking the lead of N-doped CuO as an absorber material for optoelectronics.

Impact of nitrogen doping on physical properties of CuO thin films fabricated by RF reactive sputtering using a pure Cu target for solar cell application

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.