| AVS 64th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology Division | Monday Sessions |
| Session NS+HC+SS-MoA |
| Session: | Oxides in Nanotechnology |
| Presenter: | Yingge Du, Pacific Northwest National Laboratory |
| Authors: | Y. Du, Pacific Northwest National Laboratory Z. Yang, Pacific Northwest National Laboratory Z.H. Zhu, Pacific Northwest National Laboratory C. Wang, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
Tungsten trioxide (WO3) based thin-film materials are of significant importance because of their diverse structures and wide range of properties. These materials have found widespread applications in display devices, electrochromic “smart” windows, gas sensors, catalysis, and photocatalysis. Investigations of WO3 films in epitaxial form offer definite advantages over porous or polycrystalline forms for fundamental science studies. For example, the ability to detect and eliminate secondary phases and surfaces simplifies the material system and makes it easier to establish defensible cause-and-effect relationships. While amorphous, polycrystalline, and epitaxial WO3 films have been prepared by several methods such as evaporation of WO3, sputtering, and pulsed laser deposition, the growth of epitaxial WO3 films by molecular beam epitaxy (MBE) is much less explored.
We examined three different ways to grow epitaxial WO3 films by MBE – by evaporating WO3 powders from an effusion cell, by evaporating WOx surface layers formed on W metal surface, and by evaporating tungsten metal in an oxidizing environment. Epitaxial films are formed in all three cases but the growth characteristics vary significantly. The films from the first two methods are found to grow as stoichiometric islands first, while the third method leads to layer by layer growth, with significant amount of ordered oxygen vacancies. The films are characterized in-situ by RHEED and XPS, and ex-situ by XRD, SIMS, and STEM.