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Thin films are utilized in various applications, including LEDs, solar cells, and microelectronics. Technological advancements necessitate the development of increasingly thinner materials. Researchers in this field face the challenges of developing advanced materials. One approach to address this is by devising new process strategies that enable the synthesis of new materials. This thesis explores the conformal chemical vapor deposition of boron carbide thin films, highlighting the various strategies developed to achieve conformal thin film depositions on intricate morphologies. These materials find applications in solid-state neutron detectors as a neutron converter layer, in the encapsulation of carbon nanotubes, and as free-standing tubular material grown on carbon nanotubes. Triethyl boron (TEB, B(C2H5)3) was used as a single source precursor, with its hydrocarbon ligand serving as the carbon source. By limiting the reaction kinetics, excellent conformality with a B-rich composition of B5.2C was achieved in 10:1 aspect ratio structure at 450 °C. The process was further explored with complex morphologies and various temperature regimes, adopting further strategies for the desired characteristics. The kinetically limited growth regime is a compromise between achieving good film conformality at a lower temperature and obtaining higher density at higher temperature. Competitive co-diffusion as a new strategy with the prospect of improving the step coverage at higher temperatures for better film properties was experimented. Using a heavy inert gas (Xe) as a diffusion additive enabled conformal deposition at 550 °C by enhancing the step coverage from 0.71 to 0.97 in 10:1 aspect ratio feature. This process was further tested to encapsulate random oriented carbon nanotubes (CNT) within a membrane structure, achieving uniform deposition B4C thin films without clogging pore sites and allowing tunable porosity. The compatibility observed for B4C thin film growth on CNT su, 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.

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/)., 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]

Neutron detection is of great importance in many fields spanning from scientific research, to nuclear science, and to medical application. The development of silicon-based neutron detectors with enhanced neutron detection efficiency can offer several advantages such as spatial resolution, enhanced dynamic range and background discrimination. In this work, increased detection efficiency is pursued by fabricating high aspect ratio 3D micro-structures filled with neutron converting materials (B4C) on planar silicon detectors. An in-depth feasibility study was carried out in all aspects of the sensor fabrication technology. Passivation of the etched structures was studied in detail, to ensure good electrical performance. The conformal deposition of B4C with a newly developed process showed excellent results. Preliminary electrical characterisation of the completed devices is promising, and detectors have been mounted on dedicated boards in view of the upcoming tests with neutrons., Funding Agencies|Research Council of Norway [289437]; Swedish Research Council [2018-05499]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials (AFM) at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]

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, 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.