Mapping the Structure of Oxygen-Doped Wurtzite Aluminum Nitride Coatings from Ab Initio Random Structure Search and Experiments
| Autor: | Daniele Scopece, Hans J. Hug, Maciej Oskar Liedke, Maik Butterling, Carlo A. Pignedoli, Piero Gasparotto, Maria Fischer, Mathis Trant, Andreas Wagner, Daniele Passerone, Oguz Yildirim |
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| Rok vydání: | 2021 |
| Předmět: |
Materials science
010304 chemical physics Doping Ab initio 02 engineering and technology Crystal structure Nitride 021001 nanoscience & nanotechnology 01 natural sciences Chemical physics Metastability 0103 physical sciences X-ray crystallography General Materials Science Grain boundary 0210 nano-technology Wurtzite crystal structure |
| Zdroj: | ACS Applied Materials & Interfaces. 13:5762-5771 |
| ISSN: | 1944-8252 1944-8244 |
| DOI: | 10.1021/acsami.0c19270 |
| Popis: | Machine learning is changing how we design and interpret experiments in materials science. In this work, we show how unsupervised learning, combined with ab initio random structure searching, improves our understanding of structural metastability in multicomponent alloys. We focus on the case of Al-O-N alloys where the formation of aluminum vacancies in wurtzite AlN upon the incorporation of substitutional oxygen can be seen as a general mechanism of solids where crystal symmetry is reduced to stabilize defects. The ideal AlN wurtzite crystal structure occupation cannot be matched due to the presence of an aliovalent hetero-element into the structure. The traditional interpretation of the c-lattice shrinkage in sputter-deposited Al-O-N films from X-ray diffraction (XRD) experiments suggests the existence of a solubility limit at 8 at % oxygen content. Here, we show that such naive interpretation is misleading. We support XRD data with accurate ab initio modeling and dimensionality reduction on advanced structural descriptors to map structure-property relationships. No signs of a possible solubility limit are found. Instead, the presence of a wide range of non-equilibrium oxygen-rich defective structures emerging at increasing oxygen contents suggests that the formation of grain boundaries is the most plausible mechanism responsible for the lattice shrinkage measured in Al-O-N sputtered films. We further confirm our hypothesis using positron annihilation lifetime spectroscopy. |
| Databáze: | OpenAIRE |
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