HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO<sub>2</sub>/LaAlO<sub>3</sub> Heterointerface
The understanding of the origin of a two-dimensional electron gas (2DEG) at the surface of anatase TiO<sub>2</sub> remains a challenging issue. In particular, in TiO<sub>2</sub> ultra-thin films, it is extremely difficult to distinguish intrinsic effects, due to the physics o...
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MDPI AG
2022-01-01
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| Online Access: | https://www.mdpi.com/2076-3417/12/3/1489 |
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| author | Mahabul Islam Piu Rajak Daniel Knez Sandeep Kumar Chaluvadi Pasquale Orgiani Giorgio Rossi Goran Dražić Regina Ciancio |
| author_facet | Mahabul Islam Piu Rajak Daniel Knez Sandeep Kumar Chaluvadi Pasquale Orgiani Giorgio Rossi Goran Dražić Regina Ciancio |
| author_sort | Mahabul Islam |
| collection | DOAJ |
| description | The understanding of the origin of a two-dimensional electron gas (2DEG) at the surface of anatase TiO<sub>2</sub> remains a challenging issue. In particular, in TiO<sub>2</sub> ultra-thin films, it is extremely difficult to distinguish intrinsic effects, due to the physics of the TiO<sub>2</sub>, from extrinsic effects, such as those arising from structural defects, dislocations, and the presence of competing phases at the film/substrate interface. It is, therefore, mandatory to unambiguously ascertain the structure of the TiO<sub>2</sub>/substrate interface. In this work, by combining high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), density functional theory calculations, and multislice image simulations, we have investigated the nature of strainless anatase TiO<sub>2</sub> thin films grown on LaAlO<sub>3</sub> substrate. In particular, the presence of oxygen vacancies in anatase TiO<sub>2</sub> has been proved to stabilize the formation of an extra alloy layer, Ti<sub>2</sub>AlO<sub>4</sub>, by means of interface rearrangement. Our results, therefore, elucidate why the growth of anatase TiO<sub>2</sub> directly on LaAlO<sub>3</sub> substrate has required the deposition of a TiO<sub>x</sub> extra-layer to have a 2DEG established, thus confirming the absence of a critical thickness for the TiO<sub>2</sub> to stabilize a 2DEG at its surface. These findings provide fundamental insights on the underlying formation mechanism of the 2DEG in TiO<sub>2</sub>/LAO hetero-interfaces to engineer the 2DEG formation in anatase TiO<sub>2</sub> for tailored applications. |
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| language | English |
| last_indexed | 2024-03-10T00:12:14Z |
| publishDate | 2022-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Applied Sciences |
| spelling | doaj.art-922f1b6ae1b04979b1e7e2c0b66efecb2023-11-23T15:58:27ZengMDPI AGApplied Sciences2076-34172022-01-01123148910.3390/app12031489HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO<sub>2</sub>/LaAlO<sub>3</sub> HeterointerfaceMahabul Islam0Piu Rajak1Daniel Knez2Sandeep Kumar Chaluvadi3Pasquale Orgiani4Giorgio Rossi5Goran Dražić6Regina Ciancio7Istituto Officina dei Materiali-CNR, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, ItalyIstituto Officina dei Materiali-CNR, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, ItalyInstitute for Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz, AustriaIstituto Officina dei Materiali-CNR, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, ItalyIstituto Officina dei Materiali-CNR, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, ItalyIstituto Officina dei Materiali-CNR, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, ItalyDepartment of Materials Chemistry, National Institute of Chemistry, 1001 Ljubljana, SloveniaIstituto Officina dei Materiali-CNR, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, ItalyThe understanding of the origin of a two-dimensional electron gas (2DEG) at the surface of anatase TiO<sub>2</sub> remains a challenging issue. In particular, in TiO<sub>2</sub> ultra-thin films, it is extremely difficult to distinguish intrinsic effects, due to the physics of the TiO<sub>2</sub>, from extrinsic effects, such as those arising from structural defects, dislocations, and the presence of competing phases at the film/substrate interface. It is, therefore, mandatory to unambiguously ascertain the structure of the TiO<sub>2</sub>/substrate interface. In this work, by combining high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), density functional theory calculations, and multislice image simulations, we have investigated the nature of strainless anatase TiO<sub>2</sub> thin films grown on LaAlO<sub>3</sub> substrate. In particular, the presence of oxygen vacancies in anatase TiO<sub>2</sub> has been proved to stabilize the formation of an extra alloy layer, Ti<sub>2</sub>AlO<sub>4</sub>, by means of interface rearrangement. Our results, therefore, elucidate why the growth of anatase TiO<sub>2</sub> directly on LaAlO<sub>3</sub> substrate has required the deposition of a TiO<sub>x</sub> extra-layer to have a 2DEG established, thus confirming the absence of a critical thickness for the TiO<sub>2</sub> to stabilize a 2DEG at its surface. These findings provide fundamental insights on the underlying formation mechanism of the 2DEG in TiO<sub>2</sub>/LAO hetero-interfaces to engineer the 2DEG formation in anatase TiO<sub>2</sub> for tailored applications.https://www.mdpi.com/2076-3417/12/3/1489anatase TiO<sub>2</sub>2DEGoxygen vacanciesheterointerfacesaberration-corrected scanning transmission electron microscopyDFT calculations |
| spellingShingle | Mahabul Islam Piu Rajak Daniel Knez Sandeep Kumar Chaluvadi Pasquale Orgiani Giorgio Rossi Goran Dražić Regina Ciancio HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO<sub>2</sub>/LaAlO<sub>3</sub> Heterointerface Applied Sciences anatase TiO<sub>2</sub> 2DEG oxygen vacancies heterointerfaces aberration-corrected scanning transmission electron microscopy DFT calculations |
| title | HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO<sub>2</sub>/LaAlO<sub>3</sub> Heterointerface |
| title_full | HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO<sub>2</sub>/LaAlO<sub>3</sub> Heterointerface |
| title_fullStr | HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO<sub>2</sub>/LaAlO<sub>3</sub> Heterointerface |
| title_full_unstemmed | HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO<sub>2</sub>/LaAlO<sub>3</sub> Heterointerface |
| title_short | HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO<sub>2</sub>/LaAlO<sub>3</sub> Heterointerface |
| title_sort | haadf stem and ab initio calculations investigation of anatase tio sub 2 sub laalo sub 3 sub heterointerface |
| topic | anatase TiO<sub>2</sub> 2DEG oxygen vacancies heterointerfaces aberration-corrected scanning transmission electron microscopy DFT calculations |
| url | https://www.mdpi.com/2076-3417/12/3/1489 |
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