RT journal article
T1 Spectroscopic Ellipsometry Study on Tuning the Electrical and Optical Properties of Zr-Doped ZnO Thin Films Grown by Atomic Layer Deposition
A1 Bohórquez, Carolina
A1 Bakkali, Hicham
A1 Delgado Jaén, Juan José
A1 Blanco Ollero, Eduardo
A1 Herrera, Manuel
A1 Domínguez de la Vega, Manuel
A2 Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica
A2 Física de la Materia Condensada
K1 Zr-doped ZnO
K1 ALD
K1 spectroscopic ellipsometry
K1 optical properties
K1 free carrier density
K1 Drude−TL model
AB This work reports the ellipsometry analysis of atomic layer deposition (ALD) films of ZnO doped with Zr to determine parameters like free carrier concentration and mobility. Thin films of zinc oxide (ZnO) and Zr-doped ZnO of thickness similar to 100 nm were prepared by atomic layer deposition on sapphire, SiO2/Si(100), and Si(100) substrates. Variable-angle spectroscopic ellipsometry was used to study their optical properties in the 0.5-3.5 eV spectral range. The optical constants were accurately obtained using a model that combines Drude and Tauc-Lorentz oscillators with Bruggeman effective medium approximations, allowing the inclusion of a roughness layer in the optical model. The effect of Zr doping (ca. 1.9- 4.4 atom %) was then investigated in both as- prepared samples and samples annealed in the temperature range of 100-300 degrees C. All of the films exhibited good optical transparency (ca. 70-90% in the visible region). For doping levels below 2.7 atom %, the real part of the dielectric permittivity reveals a semiconductor-to-metal transition in the near-infrared (NIR) region, as the permittivity goes from positive to negative. Besides, the plasma energy increases with increasing Zr concentration, and both resistivity and carrier concentration exhibit slightly parabolic behaviors, with a minimum of similar to 1.5 x 10(-3) Omega cm and a maximum of 2.4 x 10(20) cm(-3), respectively, at the same critical Zr concentration (2.7 atom %). In contrast, the carrier mobility decreases rapidly from 76.0 to 19.2 cm(2)/(V s) with increasing Zr content, while conductivities and carrier mobilities worsen when the annealing temperature increases, probably due to the segregation of ZnO crystals. Finally, the optical band gap is very stable, revealing its interesting independence of substrate composition and annealing temperature, as it collapses to a single master curve when band gap energy is plotted versus free carrier concentration, following the Burstein-Moss effect. Overall, the Zr-doped ZnO films studied here would be a highly desirable system for developing thermally stable transparent conductive oxides (TCOs).
PB AMER CHEMICAL SOC
YR 2022
FD 2022-03
LK http://hdl.handle.net/10498/27028
UL http://hdl.handle.net/10498/27028
LA eng
DS Repositorio Institucional de la Universidad de Cádiz
RD 10-nov-2026