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4. Self-regulating plasma-assisted growth of epitaxial BaBiO3 thin-film on SrTiO3-buffered Si(001) substrate.

Author

Ahmed, I., De Gendt, S., and Merckling, C.

Subjects
*MOLECULAR beam epitaxy, *REACTIVE oxygen species, *BUFFER layers, *SUPERCONDUCTIVITY, *DOPING agents (Chemistry), *EPITAXY
Abstract

The BaBiO3 perovskite oxide is an interesting material system because of its superconductivity when p-doped and the predicted topological insulating nature when n-doped. Single crystalline BaBiO3 films are grown by molecular beam epitaxy with high quality utilizing the adsorption-controlled regime, where volatile Bi is supplied in excess in the presence of oxygen radicals. BaBiO3 films are integrated on Si(001) substrates through growth on a SrTiO3(001) buffer layer. Despite the 11.77% lattice mismatch, by systematically varying growth parameters, such as plasma conditions, substrate temperature, and metallic fluxes, a growth window for the BaBiO3 is well-established. Within the optimum growth window, films are stoichiometric and of high crystalline quality based on the different physical characterization techniques. The development of robust layers is facilitated by accessing the self-regulating regime, where only the stoichiometric quantity of Bi sticks during the epitaxy. [ABSTRACT FROM AUTHOR]

Published
2022
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7. Enhancing dielectric passivation on monolayer WS2 via a sacrificial graphene oxide seeding layer.

Author

Wyndaele, P.-J., de Marneffe, J.-F., Sergeant, S., de la Rosa, C. J. L., Brems, S., Caro, A. M., and De Gendt, S.

Subjects
GRAPHENE oxide, PASSIVATION, MONOMOLECULAR films, SURFACE chemistry, DIELECTRICS, CHARGE transfer, OXYGEN
Abstract

The full utilization of two-dimensional transition metal dichalcogenides (2D TMDCs) faces several challenges, among which is realizing uniform material deposition on the 2D surface. Typical strategies to enable material growth lead to a poor interface quality, degrading the 2D TMDC's properties. In this work, a sacrificial, graphene oxide-based seeding layer is used (1) as passivation layer, protecting the underlying 2D TMDC and (2) as nucleation layer, enabling uniform material growth. Graphene is transferred on monolayer WS2, establishing a high-quality van der Waals interface. After transfer, the polymeric residues on graphene are cleaned via a combination of wet- and dry treatments and functionalized via dry UV/O3 oxidation. The rate of graphene oxidation is shown to be substrate dependent, which is explained by UV light-induced ultrafast charge transfer between the graphene and WS2 monolayer. The carbon-oxygen functionalities serve as nucleation sites in a subsequent HfO2 ALD process, achieving more uniform dielectric growth and faster layer closure compared to direct deposition. The graphene-based nucleation- / passivation approach offers adaptability, allowing for tailored surface chemistry to enable any alternative material growth, while maintaining a prefect van der Waals interface. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Influence of thickness scaling on the electronic structure and optical properties of oxygen deficient BaBiO3-δ thin films grown on SrTiO3-buffered Si(001) substrate.

Author

Ahmed, I., Korytov, M., Sergeant, S., Nuytten, T., Conard, T., De Gendt, S., and Merckling, C.

Subjects
OPTICAL properties, VALENCE (Chemistry), THIN films, OCTAHEDRA, ELECTRONIC structure, OXYGEN
Abstract

BaBiO3 has attracted a lot of research attention since it was discovered as the parent compound for the high-Tc superconducting BaPbxBi1–xO3 and Ba1–xKxBiO3. In its pure state, BaBiO3 is an insulator due to the presence of a breathing distortion of the BiO6 octahedra. The distortion is attributed to the valency of Bi in the compound being charge-ordered in the form of Bi3+ and Bi5+ along the lattice, resulting in alternating expanded or contracted BiO6 octahedra. The interaction between the electronic properties and the thickness of the thin film is crucial to study. We conducted a thorough study to investigate the effect of the thickness reduction of BaBiO3-δ grown on SrTiO3-buffered Si substrates on the optical properties as well as the Bi electronic structure of the thin films. We conclude that modifications in the valency of Bi in the ultra-thin film regime result in an optically conducting layer. [ABSTRACT FROM AUTHOR]

Published
2024
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15. Fabrication of MBE High-κ MOSFETs in a Standard CMOS Flow

Author

Pantisano, L., Conard, T., Scram, T., Deweerd, W., De Gendt, S., Heyns, M., Rittersma, Z. M., Marchiori, C., Sousa, M., Fompeyrine, J., Locquet, J. -P., Itoh, Kiyoo, editor, Lee, Thomas, editor, Sakurai, Takayasu, editor, Sansen, Willy M. C., editor, Schmitt-Landsiedel, Doris, editor, Dimoulas, Athanasios, editor, Gusev, Evgeni, editor, McIntyre, Paul C., editor, and Heyns, Marc, editor

Published
2007
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38. Plasma enhanced atomic layer etching of high-k layers on WS2.

Author

de Marneffe, J.-F., Marinov, D., Goodyear, A., Wyndaele, P.-J., St. J. Braithwaite, N., Kundu, S., Asselberghs, I., Cooke, M., and De Gendt, S.

Subjects
ETCHING, PLASMA flow, TRANSITION metals
Abstract

The etching of HfO 2 and ZrO 2 high-k dielectrics is studied using plasma enhanced atomic layer etching. The etching method relies on a continuous argon inductively coupled plasma discharge in which reactive gases are pulsed, followed by substrate biasing; both steps are separated by purge periods. It is found that pure BCl 3 is too chemically active while a Cl 2 –BCl 3 allows a high process synergy; in addition, the latter gives a high selectivity to SiO 2. The optimal etch conditions are applied to high-k layers deposited on top of WS 2 transition metal dichalcogenide. Postetch analysis shows negligible tungsten and sulfur depletion as well as negligible change in optical (Raman) response of the 2D layer, indicating that atomic layer etching concepts allows us to prevent WS 2 material loss or damage. [ABSTRACT FROM AUTHOR]

Published
2022
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39. Flatband voltage shift of ruthenium gated stacks and its link with the formation of a thin ruthenium oxide layer at the ruthenium/dielectric interface

Author

Z. Li; Schram, T., Pantisano, L., Conard, T., Van Elshocht, S., Deweerd, W., De Gendt, S., De Mayer, K., Stesmans, A., Sahmuilia, S., Afanas'Ev, V.. V., Akheyar, A., Brunco, D. P., Yamada, N., and Lehnen, P.

Subjects
Ruthenium -- Electric properties, Dielectric films -- Electric properties, Thin films -- Electric properties, Oxides -- Electric properties, Time-of-flight mass spectrometry -- Usage, Physics
Abstract

The article analyses the flatband voltage shift of ruthenium (Ru) gated metal-oxide-semiconductor stacks and its effects on the formation of thin Ru oxide layer at the dielectric interface after a thermal treatment with oxygen. It reveals that an increase in the voltage shifts for Ru gated stacks is the result of the formation of the thin Ru-oxide layer, which is found to be thermodynamically very much similar to the bulk Ru[O.sub.2].

Published
2007

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