Tailorable properties of Nd-doped ZnO epitaxial thin films for optoelectronic and plasmonic devices

• Published in: Optical materials 2022-04, Vol.126, p.112154, Article 112154
• Main Authors: Nistor, Magdalena, Gherendi, Florin, Perrière, Jacques
• Format: Article
• Language: English
• Subjects: Degenerate semiconductor; Epsilon-near-zero; Metal-insulator transition; Physics; Plasmonics; Transparent conducting oxide; ZnO
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2022.112154

Transparent conductive oxides with both low resistivity and high transparency in the visible and near-infrared wavelengths are required for solar cells and plasmonic applications. In this work we demonstrate that highly conducting and transparent Nd:ZnO thin films have been grown on c-cut sapphire single crystal substrates by pulsed electron beam deposition under argon (10−2 mbar). At 2% at. Nd doping, these films crystallize in the wurtzite structure at T > 300 °C, with well-defined epitaxial relationships with the c-cut sapphire as a function of the substrate temperature. The improvement of the film structural quality with increasing growth temperature led to the lowest resistivity value of 5.12 × 10−4 Ωcm and highest transparency that were maintained more than 36 months under ambient conditions. X-ray photoelectron valence band measurements revealed that the dominant Zn-polar face of Nd:ZnO thin films explains the improved electrical properties. The dielectric functions of films were determined and show that these films are suitable as transparent contact electrodes for solar cell devices or tunable epsilon-near-zero materials for plasmonics. •Epitaxial 2% at. Nd doped ZnO thin films grown by pulsed electron beam deposition.•The lowest resistivity value of 5.12 × 10−4 Ωcm reported for Nd doped ZnO thin films.•Remarkable stability in time of films due to Nd doping and epitaxial growth.•Highly degenerate semiconductor and epsilon-near-zero Nd doped ZnO thin films.