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Conformal chemical vapor deposition of boron-rich boron carbide thin films from triethylboron
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-8469-5983
Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-7171-5383
2023 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 41, no 1, article id 013401Article in journal (Refereed) Published
Abstract [en]

We report conformal chemical vapor deposition (CVD) of boron carbide (BxC) thin films on silicon substrates with 8:1 aspect-ratio morphologies, using triethylboron [B(C2H5)(3)] as a single source CVD precursor. Step coverage (SC) calculated from the cross-sectional scanning electron microscopy measurements shows that films deposited at & LE;450 & DEG;C were highly conformal (SC = 1). We attribute this to the low reaction probability at low substrate temperatures enabling more gas phase diffusion into the features. The chemical state of the material, determined by x-ray photoelectron spectroscopy, shows as a carbide with B-B, B-C, C-B, and C-C chemical bonds. Quantitative analysis by time-of-flight elastic recoil detection analysis reveals that films deposited at 450 & DEG;C are boron-rich with around 82.5 at. % B, 15.6 at. % C, 1.3 at. % O, and 0.6 at. % H, i.e., about B5C. The film density as measured by x-ray reflectometry varies from 1.9 to 2.28 g/cm(3) depending on deposition temperature. (C) 2022 Author(s).All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY)license (http://creativecommons.org/licenses/by/4.0/).

Place, publisher, year, edition, pages
A V S AMER INST PHYSICS , 2023. Vol. 41, no 1, article id 013401
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-190923DOI: 10.1116/6.0002203ISI: 000894732600002OAI: oai:DiVA.org:liu-190923DiVA, id: diva2:1724737
Note

Funding Agencies|Swedish Research Council (VR) [2018-05499]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University [2009-00971]; Swedish research council VR-RFI [2019-00191]

Available from: 2023-01-09 Created: 2023-01-09 Last updated: 2023-11-09
In thesis
1. Conformal chemical vapor deposition of boron carbide thin films
Open this publication in new window or tab >>Conformal chemical vapor deposition of boron carbide thin films
2023 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The sustainability goals of the modern world and the fascinating properties of sub-micron scale materials promote development of materials in thin film form. Thin films are materials that have thicknesses ranging from sub-nanometer to several micrometers, synthesized by various deposition techniques. They are used for diverse applications, such as light emitting diodes, solar cells, semiconductor chips, etc. The primary objective of this research project is to develop a chemical vapor deposition (CVD) process for conformal boron carbide thin films. Since boron carbide is a promising neutron converter material for solid-state neutron detectors, the process was validated by depositing on prototype detector chips.  

In this study, triethylboron (TEB) was used as single source CVD precursor to deposit boron carbide thin films. The initial experiments focused on low reaction rate deposition by depositing in a kinetically limited regime. The films deposited at ≤450 °C in 8:1 aspect ratio micro-trench structures were highly conformal and show a stoichiometry of about B5.2C. We attribute this observed conformality to the slow reaction kinetics of the TEB at the low deposition temperature enabling the diffusive transport of the precursor molecule down the trench. The depositions carried out on the prototype detector-chips show promising results.  

We expand our studies to investigate a new strategy with the prospect of improving the step coverage at higher temperatures for better film properties. We hypothesize that adding a suitable heavier molecule, diffusion additive, with an appropriate partial pressure can enhance the step coverage by pushing the lighter precursor molecule via competitive co-diffusion. It was tested by adding Xe gas to the boron carbide CVD from TEB. The result shows that with this diffusion additive the step coverage was improved from 0.71 to 0.97. From our experimental results, we suggest a competitive diffusion model that can be adapted to other CVD processes to enhance the film step coverage.  

The CVD process is further validated by depositing onto carbon nanotube membranes. The initial results show that the process was able to afford evenly deposition around the individual nanotubes in the carbon nanotube membrane. Raman spectroscopy measurements show a similar D-band to G-band intensity ratio before and after the deposition indicating that no defects were induced in the nanotubes.      

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2023. p. 48
Series
Linköping Studies in Science and Technology. Licentiate Thesis, ISSN 0280-7971 ; 1978
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-199076 (URN)10.3384/9789180754545 (DOI)9789180754538 (ISBN)9789180754545 (ISBN)
Opponent
Supervisors
Note

Funding: Financial support by the Swedish Research Council (VR) and from the Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linköping University have supported my studies and are gratefully acknowledged. 

Available from: 2023-11-09 Created: 2023-11-09 Last updated: 2023-11-13Bibliographically approved

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