Comprehensive Optoelectronic Study of Copper Nitride:Dielectric Function and Bandgap Energies.

Abstract

Copper nitride (Cu3N) is gaining attention as an eco-friendly thin-film semiconductor in a

myriad of applications, including storage devices, microelectronic components, photodetectors,

and photovoltaic cells. This work presents a detailed optoelectronic study of Cu3N

thin films grown by reactive RF-magnetron sputtering under pure N2. An overview of the

state-of-the-art literature on this material and its potential applications is also provided. The

studied films consist of Cu3N polycrystals with a cubic anti-ReO3 type structure exhibiting

a preferential (100) orientation. Their optical properties across the UV-Vis-NIR spectral

range were investigated using a combination of multi-angle spectroscopic ellipsometry,

broadband transmission, and reflection measurements. Our model employs a stratified

geometrical approach, primarily to capture the depth-dependent compositional variations

of the Cu3N film while also accounting for surface roughness and the underlying glass

substrate. The complex dielectric function of the film material is precisely determined

through an advanced dispersion model that combines multiple oscillators. By integrating

the Tauc–Lorentz, Gaussian, and Drude models, this approach captures the distinct

electronic transitions of this polycrystal. This customized optical model allowed us to

accurate extract both the indirect (1.83–1.85 eV) and direct (2.38–2.39 eV) bandgaps. Our

multifaceted characterization provides one of the most extensive studies of Cu3N thin films

to date, paving the way for optimized device applications and broader utilization of this

promising binary semiconductor, and showing its particular potential for photovoltaic

given its adequate bandgap energies for solar applications.