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A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates
Published on: May 9, 2014
Molecular layer deposition of thiol-ene multilayers on semiconductor surfaces
Yun-hui Li1, Dong Wang, Jillian M Buriak
1Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada.
Langmuir : the ACS Journal of Surfaces and Colloids
|November 3, 2009
Summary
Molecular layer deposition (MLD) enables precise vertical chemical structure control in organic thin films. This covalent layer-by-layer assembly method offers a pathway for advanced organic electronics and functional materials.
Area of Science:
- Materials Science
- Organic Chemistry
- Surface Science
Background:
- Controlled vertical chemical structure in organic thin films is crucial for applications in organic electronics, chemical-resistant coatings, and biocompatible materials.
- Existing methods for fabricating such films often face challenges in achieving precise compositional control along the surface normal (z-direction).
Purpose of the Study:
- To investigate the feasibility of molecular layer deposition (MLD) for fabricating organic thin films with controlled chemical structure in the vertical direction.
- To explore the influence of molecular structure and substrate type on film growth and self-limiting behavior during MLD.
Main Methods:
- Utilized UV-induced thiol-ene reactions for covalent layer-by-layer assembly (MLD) of organic thin films.
- Deposited films on silicon, silicon oxide, and germanium substrates using successive exposures to dithiol and diene molecules under UV irradiation at room temperature.
- Characterized film thickness, surface morphology, and chemical composition using ellipsometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM).
Main Results:
- Achieved well-defined organic thin films through MLD with short UV exposure times (approx. 30 min).
- Observed linear increases in film thickness with the number of deposited layers for shorter aliphatic dithiols and dienes (C <= 8).
- Identified a self-limiting growth mechanism for longer molecules and aromatic substrates, where both ends of the molecule react with the surface, arresting further growth.
Conclusions:
- Molecular layer deposition via UV-induced thiol-ene reactions provides a viable method for fabricating organic thin films with controlled vertical chemical structure.
- The growth behavior of MLD films is dependent on molecular length and substrate chemistry, with self-limiting growth observed under specific conditions.
- This technique holds promise for creating tailored organic materials for diverse technological applications.
