In- and out-plane transport properties of chemical vapor deposited TiO2 anatase films

• Published in: Journal of materials science 2021-06, Vol.56 (17), p.10458-10476
• Main Authors: Miquelot, A., Youssef, L., Villeneuve-Faure, C., Prud’homme, N., Dragoe, N., Nada, A., Rouessac, V., Roualdes, S., Bassil, J., Zakhour, M., Nakhl, M., Vahlas, C.
• Format: Article
• Language: English
• Subjects: Anatase; Carrier mobility; Characterization and Evaluation of Materials; Chemical vapor deposition; Chemistry and Materials Science; Classical Mechanics; Columnar structure; Crystallography and Scattering Methods; Dynamic random access memory; Electrical properties; Electrical resistivity; Electronic Materials; Functional materials; Grain size; Low temperature; Materials Science; Metalorganic chemical vapor deposition; Microbalances; Morphology; Organic chemicals; Organic chemistry; Plasma enhanced chemical vapor deposition; Polymer Sciences; Polymorphism; Porosity; Random access memory; Solid Mechanics; Titanium dioxide; Transport properties; Water splitting
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-021-05955-6

Due to their polymorphism, TiO 2 films are quintessential components of state-of-the-art functional materials and devices for various applications from dynamic random access memory to solar water splitting. However, contrary to other semiconductors/dielectric materials, the relationship between structural/morphological and electrical properties at the nano and microscales remains unclear. In this context, the morphological characteristics of TiO 2 films obtained by metal–organic chemical vapor deposition (MOCVD) and plasma-enhanced chemical vapor deposition (PECVD), the latter including nitrogen doping, are investigated and they are linked to their in- and out-plane electrical properties. A transition from dense to tree-like columnar morphology is observed for the MOCVD films with increasing deposition temperature. It results in the decrease in grain size and the increase in porosity and disorder, and subsequently, it leads to the decrease in lateral carrier mobility. The increase in nitrogen amount in the PECVD films enhances the disorder in their pillar-like columnar morphology along with a slight increase in density. A similar behavior is observed for the out-plane current between the low temperature MOCVD films and the undoped PECVD ones. The pillar-like structure of the latter presents a lower in-plane resistivity than the low temperature MOCVD films, whereas the out-plane resistivity is lower. The tree-like columnar structure exhibits poor in- and out-plane conductivity properties, whereas pillar-like and dense TiO 2 exhibits similar in- and out-plane conductivities even if their morphologies are noticeably different. Graphical Abstract