Atomic/molecular layer deposition of Ti-organic thin films using sustainable Ti precursor

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School of Chemical Engineering | Master's thesis
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Date

2024-09-09

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Chemistry

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Degree programme

Master's Programme in Chemical, Biochemical and Materials Engineering

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en

Pages

72

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Abstract

The growing trend towards hybrid inorganic-organic materials has led to the pursuit of advanced thin film technologies. Atomic layer deposition (ALD) is a pivotal technique for depositing inorganic thin films. At the same time, its extension Atomic/Molecular Layer Deposition (ALD/MLD) allows the deposition of hybrid inorganic-organic thin films by relying on the fundamental self-limiting gas phase reactions and creating new materials that conventional methods cannot achieve. This thesis investigates two new routes for the deposition of Titanium-Hydroquinone (Ti-HQ) and Titanium Terephthalic Acid (Ti-TPA) thin films, using ALD/MLD. An alternative metal precursor, titanium tetra isopropoxide (Ti(OiPr)₄) was utilized to avoid the traditional halogen-based precursor titanium tetrachloride (TiCl4), providing a more environmentally friendly and safer methodology. The deposition processes were optimized by varying parameters such as pulse/purge sequences, temperature, and deposition cycle numbers to achieve high-quality films with desired thickness and uniformity. Comprehensive characterization techniques were employed for the analysis of thin films. Moreover, the growth behavior of the Ti-HQ thin film was studied further on five different polymers Polystyrene (PS), Polyethene oxide (PEO), Poly(3-hexylthiophene) (P3HT), Poly(4-vinylpyridine) (P4VP), and Polymethyl methacrylate (PMMA) which are potential homopolymers for the creation of block copolymers (BCPs). BCP templates have garnered significant interest for patterned growth via bottom-up methods due to their self-assembly features, where two or more chemically distinct polymers are covalently connected. Although BCPs provide exciting research, this study was solely aimed at investigating the growth behavior of Ti-HQ on the homopolymer. Our results demonstrate that Ti(OiPr)₄), effectively produces Ti-HQ and Ti-TPA thin films with excellent growth and uniformity while providing a safer and more sustainable approach. Furthermore, the depositions on polymers revealed the choice of polymer substrate significantly influenced the film growth. Thus, more studies are required on other polymer surfaces for exploring the precise growth characteristics. This will extend the studies to actual block copolymers to harness their self-assembly capabilities for patterned and area-selective depositions thus paving the way for advanced technological applications.

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Supervisor

Karppinen, Maarit

Thesis advisor

Philip, Anish

Keywords

atomic and molecular layer depositions, hybrid thin films, sustainability, polymers, HQ, TPA, PEO, P3HT, P4VP, PMMA

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https://urn.fi/URN:NBN:fi:aalto-202411217238

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[dipl] Kemian tekniikan korkeakoulu / CHEM