Annealing treatment effects on the optical and electrical properties of Al-doped zinc oxide thin films
Jorge Trevejo-Pinedo a, Fabiola Bravo-Hualpa b, Erik Perez b, Luis Enrique b, Miguel Piñeiro b, Paul Llontop b, María R. Sun-Kou a, Jorge Andres Guerra b
a Sección Química, Departamento Académico de Ciencias, Pontificia Universidad Católica del Perú
b Sección Física, Departamento Académico de Ciencias, Pontificia Universidad Católica del Perú
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Fall 2023 Conference (MATSUSFall23)
#NANOFUN - Functional Nanomaterials: from optoelectronics to bio- and quantum applications
Torremolinos, Spain, 2023 October 16th - 20th
Organizers: Milena Arciniegas, Iwan Moreels and Gabriele Raino
Oral, Jorge Trevejo-Pinedo, presentation 223
Publication date: 18th July 2023

Transparent conductive oxides (TCOs) are materials of particular interest in the electronics industry. For instance, in the manufacture of electronic devices such as high-resolution flat screens, electrochromic windows, solar cells and gas sensors. These materials simultaneously present optimal electrical (resistivity lower than 10-3 Ohm-cm) and optical properties (average transmittance greater than 80 % in the visible spectral range and a bandgap greater than 3.3 eV) [1-2]. The structural, optoelectronic and electrical properties of TCOs can be tuned by the incorporation of transition metal ions as dopants. In particular, Al-doped ZnO (ZnO:Al or AZO) is a material that has generated interest in recent years due to its potential to replace ITO, the most widely used conductive transparent oxide.

This work aims to identify the effects of aluminum doping and the post-deposition annealing treatment conditions on the structural, optical, and electrical properties of ZnO sputtered thin films. The films were deposited on silicon and fused silica (FS) substrates by radiofrequency magnetron sputtering using AZO targets (ZnO doped with 2 wt.% and 3 wt.% Al). For both Al concentrations, active cooling and non-cooling conditions were used independently for each set of substrates during the deposition process. Subsequently, post-deposition shock thermal treatments were carried out at 100, 200, 300, 400, 500 and 600 °C in an inert atmosphere of ultra-high purity argon.

Optical properties of the films were investigated through variable angle spectroscopic ellipsometry (VASE) and Ultraviolet-Visible-Near-Infrared (UV/VIS/NIR) spectrophotometry. The thickness, extinction coefficient (k), refractive index (n) and optical bandgap (Eg) of the films were determined using Drude and Tauc-Lorentz models. Point by point analysis was also used as an alternative method to determine n and k. Charge carrier density and mobility were estimated from the optical analysis.

Electrical resistivity, mobility, and charge carrier density of the films were estimated by the Van der Pauw method and Hall effect. The experimental and optically estimated values for the charge carrier density and mobility exhibit good agreement.

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