Crystalline Structure, Morphology, and Adherence of Thick TiO2 Films Grown on 304 and 316L Stainless Steels by Atomic Layer Deposition

At a Glance

Metadata	Details
Publication Date	2023-04-10
Journal	Coatings
Authors	Vagner Eduardo Caetano Marques, Lucas Augusto Manfroi, Ângela Aparecida Vieira, André Luis de Jesús Pereira, F. C. Marques
Institutions	Universidade Estadual de Campinas (UNICAMP), Instituto Tecnológico de Aeronáutica
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: Advanced Thin Film Deposition on Stainless Steel

6CCVD Analysis of: Crystalline Structure, Morphology, and Adherence of Thick TiO₂ Films Grown on 304 and 316L Stainless Steels by Atomic Layer Deposition

Executive Summary

This research successfully demonstrates the Atomic Layer Deposition (ALD) of relatively thick Titanium Dioxide (TiO₂) films onto common stainless steel alloys (AISI 304 and 316L) for biomedical and anti-corrosion applications.

High-Quality Phase Mixture: A desirable mixture of anatase and rutile phases was achieved simultaneously at a low deposition temperature (300 °C), contradicting typical literature requirements (>450 °C).
Thick Film Achievement: The ALD process, utilizing 3000 cycles, resulted in thick films (176.6 nm to 179.1 nm), significantly exceeding typical ALD thicknesses reported in similar studies.
Satisfactory Adherence: Scratch testing confirmed good film adherence, particularly on AISI 304, which maintained a low average friction coefficient (COF) of 0.2 ± 0.05 throughout the test.
Uniform Distribution: Raman mapping confirmed that both anatase and rutile phases were evenly distributed across the surface and depth of the deposited films on both substrates.
Crystallinity Improvement: The film deposited on AISI 304 showed a crystallinity improvement of approximately 82% compared to the substrate.
6CCVD Value Proposition: For applications requiring superior chemical inertness, extreme mechanical durability, or advanced electrocatalytic properties beyond metal oxides on stainless steel, 6CCVD offers high-purity Single Crystal Diamond (SCD) and Boron-Doped Diamond (BDD) materials.

Technical Specifications

The following hard data points were extracted from the experimental results, focusing on deposition parameters and material performance.

Parameter	Value	Unit	Context
Deposition Method	Atomic Layer Deposition (ALD)	N/A	TiCl₄ pulse-purge-H₂O sequence
Deposition Temperature	300	°C	Used for all 3000 cycles
Total Cycles	3000	Cycles	Resulted in thick films
Film Thickness (AISI 304)	179.1	nm	24% higher than literature reports
Film Thickness (AISI 316L)	176.6	nm	23% higher than literature reports
Film Growth Rate	0.6	Å/cycle	Consistent with ALD phenomenon
Substrate Roughness (AISI 304)	1.19	nm	Initial Ra (AFM)
Film Roughness (AISI 304)	4.35	nm	Final Ra (AFM)
Rutile Content (AISI 304)	71.15	%	Determined by XRD Rietveld refinement
Anatase Content (AISI 316L)	55.55	%	Determined by XRD Rietveld refinement
Friction Coefficient (AISI 304)	0.2 ± 0.05	N/A	Average COF during scratch test
Critical Load (AISI 316L, Lc1)	2.4	N	Load at which cohesive failure occurred

Key Methodologies

The experiment relied on a standard ALD process optimized for thick film growth and advanced material characterization.

Substrate Preparation: AISI 304 and AISI 316L stainless steel samples (10 mm diameter, 1 mm thickness) were cleaned using isopropanol and ultrapure water via ultrasonic bath.
ALD Deposition: Films were grown using a thermal ALD system. The precursors were Titanium Tetrachloride (TiCl₄, 99.995% purity) and ultrapure water (H₂O).
Cycle Sequence: 3000 cycles were performed at 300 °C using a TiCl₄ pulse (1 s), N₂ purge (1 s), H₂O pulse (250 ms), and N₂ purge (1 s) sequence.
Structural Analysis (XRD): X-ray Diffraction was used, followed by Rietveld refinement, utilizing CIF files for anatase, rutile, and austenite to determine phase percentages.
Morphological Analysis (AFM/SEM): Film thickness was measured via FEG-SEM after deliberate fracture. Surface roughness (Ra) and topography were analyzed using AFM.
Phase Distribution (Raman): Raman spectroscopy mapping was employed to confirm the presence and uniform distribution of anatase and rutile phases across the film surface and depth.
Mechanical Testing (Scratch Test): A tribometer with a Rockwell C diamond tip was used in an air environment (40% humidity) with a progressive load (0 to 5 N) to evaluate adherence and determine the friction coefficient (COF) and critical load (Lc1).

6CCVD Solutions & Capabilities

The research highlights the critical need for highly adherent, chemically stable, and structurally controlled coatings for demanding applications like biomedical implants and corrosion mitigation. 6CCVD’s MPCVD diamond materials offer a significant performance leap beyond metal oxides and stainless steel.

Research Requirement/Application	6CCVD Diamond Solution	Customization Potential & Advantage
Extreme Chemical Inertness & Biocompatibility	Optical Grade Single Crystal Diamond (SCD)	SCD offers unmatched chemical resistance and purity, ideal for long-term, non-toxic implant coatings or high-purity optical windows. Thicknesses available from 0.1 µm to 500 µm.
Advanced Electrocatalysis/Photocatalysis	Heavy Boron-Doped Diamond (BDD)	BDD is the ultimate electrode material, providing superior stability and efficiency compared to TiO₂ for advanced oxidation processes (AOPs) and sensing applications.
Large Area Coating/Substrate Needs	Polycrystalline Diamond (PCD) Wafers	6CCVD provides PCD plates and wafers up to 125 mm in diameter, suitable for scaling up industrial or large-area biomedical device production.
Ultra-Smooth Surface Finish	Precision Polishing Services	We achieve surface roughness (Ra) < 1 nm for SCD and Ra < 5 nm for inch-size PCD, ensuring optimal interfaces for subsequent thin-film deposition or direct biological contact.
Device Integration & Sensor Fabrication	Custom Metalization Services	We offer in-house deposition of critical metal layers (Au, Pt, Pd, Ti, W, Cu) required for creating robust electrical contacts or adhesion layers on diamond substrates, mirroring the integration needs of the studied TiO₂ films.
Custom Dimensions & Geometry	Laser Cutting & Substrate Fabrication	While the paper used 10 mm diameter samples, 6CCVD can provide custom dimensions and substrates up to 10 mm thick, cut to precise specifications for complex device geometries. Global shipping (DDU default, DDP available) ensures timely delivery worldwide.

Engineering Support: 6CCVD’s in-house PhD material science team specializes in optimizing diamond material selection (SCD purity, BDD doping levels, PCD grain size) for similar biomedical, anti-corrosion, and electrocatalytic projects. We provide expert consultation to transition research from metal oxides to high-performance diamond solutions.

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View Original Abstract

Titanium dioxide (TiO2) thin films are widely used in transparent optoelectronic devices due to their excellent properties, as well as in photocatalysis, cosmetics, and many other biomedical applications. In this work, TiO2 thin films were deposited onto AISI 304 and AISI 316L stainless steel substrates by atomic layer deposition, followed by comparative evaluation of the mixture of anatase and rutile phase by X-ray diffraction, Raman maps, morphology by SEM-FEG-AFM, and adhesion of the films on the two substrates, aiming to evaluate the scratch resistance. Raman spectroscopy mapping and X-ray diffraction with Rietveld refinement showed that the films were composed of anatase and rutile phases, in different percentages. Scratch testing using a diamond tip on the TiO2 film was employed to evaluate the film adherence and to determine the friction coefficient, with the results showing satisfactory adherence of the films on both substrates.

Tech Support

Original Source

DOI: https://doi.org/10.3390/coatings13040757

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