Effect of Plasma-Enhanced Atomic Layer Deposition on Oxygen Overabundance and Its Influence on the Morphological, Optical, Structural, and Mechanical Properties of Al-Doped TiO₂ Coating

• Main Authors: William Chiappim, Giorgio Testoni, Felipe Miranda, Mariana Fraga, Humber Furlan, David Ardiles Saravia, Argemiro da Silva Sobrinho, Gilberto Petraconi, Homero Maciel, Rodrigo Pessoa
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Micromachines
• Subjects: plasma-enhanced atomic layer deposition; titanium dioxide; aluminum oxide; nanolaminates; superstoichiometry; doping
• Online Access: https://www.mdpi.com/2072-666X/12/6/588

The chemical, structural, morphological, and optical properties of Al-doped TiO₂ thin films, called TiO₂/Al₂O₃ nanolaminates, grown by plasma-enhanced atomic layer deposition (PEALD) on p-type Si <100> and commercial SLG glass were discussed. High-quality PEALD TiO₂/Al₂O₃ nanolaminates were produced in the amorphous and crystalline phases. All crystalline nanolaminates have an overabundance of oxygen, while amorphous ones lack oxygen. The superabundance of oxygen on the crystalline film surface was illustrated by a schematic representation that described this phenomenon observed for PEALD TiO₂/Al₂O₃ nanolaminates. The transition from crystalline to amorphous phase increased the surface hardness and the optical gap and decreased the refractive index. Therefore, the doping effect of TiO₂ by the insertion of Al₂O₃ monolayers showed that it is possible to adjust different parameters of the thin-film material and to control, for example, the mobility of the hole-electron pair in the metal-insulator-devices semiconductors, corrosion protection, and optical properties, which are crucial for application in a wide range of technological areas, such as those used to manufacture fluorescence biosensors, photodetectors, and solar cells, among other devices.