Atomic Layer Deposition on Polymer Thin Films: On the Role of Precursor Infiltration and Reactivity

Abstract

Inorganic barriers grown by atomic layer deposition (ALD) can overcome the stability issues originating from the permeation of foreign species (water and oxygen) into polymer thin films. Alternatively, infiltration of ALD species into the bulk of the polymer can be used to modify its characteristic properties. In this study, the feasibility of growing an inorganic barrier with ALD on polystyrene, poly(methyl methacrylate), and poly(ethylene terephthalate glycol) thin films is evaluated. The nucleation and growth of the ALD layer, including the infiltration into the polymer thin film, are monitored in situ using spectroscopic ellipsometry, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy for Al 2 O 3 -ALD with trimethylaluminum as the Al precursor and H 2 O as the reactant. The results show that the deposition temperature and the presence and location of functional groups in the polymer chain exert the strongest influence on the infiltration behavior and as such allow us to manipulate (i.e. to prevent or expedite) the infiltration into the polymer thin film.

Influence of different ester side groups in polymers on the vapor phase infiltration with trimethyl aluminum

“…12 Furthermore, in a recent study it was found that VPI is also contributing to ALD processes when polymeric substrates are used. 13 The VPI mechanism consists of three steps: dissolution of the precursor in the polymer, diffusion of the precursor and by-products through the polymer structure and entrapment of the precursor by reaction with the polymer chains. 11 Thus, from a precursor point of view, apart from the typical ALD criteria volatility, thermal stability and reactivity, [14][15][16] especially shape, size and polarity of the molecule play a major role for dissolution and diffusion processes and can be tuned for the desired hybrid properties.…”

Nanometric 3D Printing of Functional Materials by Atomic Layer Deposition

“…ALD allows the preparation of thin films with a sub-nanometer thickness control, high uniformity and excellent conformality even on high aspect ratios substrates, a unique capability, as discussed in the first section of this chapter [3,[53][54][55][56][57][58]. As ALD allows the conformal coating of complex substrates with nanolayers made of an expanding [51,52]), permitting the tuning of the matrix.…”

“…As shown by numerous studies, the risk of reaction between the polymer and the precursors increases with temperature and long exposures times. In addition, the presence of functional groups in the polymer chains also increases the potential infiltration of the ALD precursors [51,52,59,[64][65][66][67][68]. Thus, even if most of the ALD processes are compatible with the coating of 3D printed objects, these considerations must be taken into account and the processes have to be tuned accordingly to coat certain 3D printed materials.…”

“…Figure 5.Illustration of the combination of 3D printing and atomic layer processing. Depending on the 3D printed material, either a coating is obtained, allowing for the tuning of the surface properties (typical ALD); or inorganic components are introduced to the subsurface of the 3D objects (atomic layer infiltration, ALI[51,52]), permitting the tuning of the matrix.…”

Al2O3 Dot and Antidot Array Synthesis in Hexagonally Packed Poly(styrene-block-methyl methacrylate) Nanometer-Thick Films for Nanostructure Fabrication

“…Atomic layer deposition (ALD) on polymers − initiated a three-dimensional (3D) growth process of inorganic materials into polymeric films known as sequential infiltration synthesis (SIS) or vapor phase infiltration (VPI). − Several studies have been published to investigate the fundamental physical chemistry of the SIS/VPI process. − The understanding of the basic mechanisms governing the process allowed expanding the list of materials that can be grown using this technique. In particular, the growth of several oxides, like Al 2 O 3 , TiO 2 , ZnO, − WO x , VO x , In 2 O 3 , , Ga 2 O 3 , and SnO 2 , has been already reported in the literature for different applications, such as high-resolution hard masks, − nanoparticle coatings and decoration, ,, superhydrophobic coatings, optical materials and antireflection coatings, , enhancer of the contrast and scattering of nanostructures, ,, 3D superlattices, oil sorbents, UV and thermal protection, tuning of mechanical propertries, sensing applications, membranes, − elastic energy-storage structures, electrical devices, ,,, and resistive switching devices .…”