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Hydroxyapatite (HA; Ca₁₀(PO₄)₆(OH)₂) coating of bone implants has many beneficial properties as it improves osseointegration and eventually becomes degraded and replaced with new bone. We prepared HA coating on a titanium substrate with atomic layer deposition (ALD) and compared monocyte differentiation and material resorption between ALD-HA and bone. After stimulation with macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor kappa-B ligand (RANKL), human peripheral blood monocytes differentiated into resorbing osteoclasts on bovine bone, but non-resorbing foreign body cells were observed on ALD-HA. The analysis of the topography of ALD-HA and bone showed no differences in wettability (water contact angle on ALD-HA 86.2° vs. 86.7° on the bone), but the surface roughness of ALD-HA (Ra 0.713 µm) was significantly lower compared to bone (Ra 2.30 µm). The cellular reaction observed on ALD-HA might be a consequence of the topographical properties of the coating. The absence of resorptive osteoclasts on ALD-HA might indicate inhibition of their differentiation or the need to modify the coating to induce osteoclast differentiation.

Background: The increasing demand for bone implants with improved osseointegration properties has prompted researchers to develop various coating types for metal implants. Atomic layer deposition (ALD) is a method for producing nanoscale coatings conformally on complex three-dimensional surfaces. We have prepared hydroxyapatite (HA) coating on titanium (Ti) substrate with the ALD method and analyzed the biocompatibility of this coating in terms of cell adhesion and viability. Methods: HA coatings were prepared on Ti substrates by depositing CaCO₃ films by ALD and converting them to HA by wet treatment in dilute phosphate solution. MC3T3-E1 preosteoblasts were cultured on ALD-HA, glass slides and bovine bone slices. ALD-HA and glass slides were either coated or non-coated with fibronectin. After 48h culture, cells were imaged with scanning electron microscopy (SEM) and analyzed by vinculin antibody staining for focal adhesion localization. An 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) test was performed to study cell viability. Results: Vinculin staining revealed similar focal adhesion-like structures on ALD-HA as on glass slides and bone, albeit on ALD-HA and bone the structures were thinner compared to glass slides. This might be due to thin and broad focal adhesions on complex three-dimensional surfaces of ALD-HA and bone. The MTT test showed comparable cell viability on ALD-HA, glass slides and bone. Conclusion: ALD-HA coating was shown to be biocompatible in regard to cell adhesion and viability. This leads to new opportunities in developing improved implant coatings for better osseointegration and implant survival.

An ambient pressure cell is described for conducting synchrotron-based x-ray photoelectron spectroscopy (XPS) measurements during atomic layer deposition (ALD) processes. The instrument is capable of true in situ and operando experiments in which it is possible to directly obtain elemental and chemical information from the sample surface using XPS as the deposition process is ongoing. The setup is based on the ambient pressure XPS technique, in which sample environments with high pressure (several mbar) can be created without compromising the ultrahigh vacuum requirements needed for the operation of the spectrometer and the synchrotron beamline. The setup is intended for chemical characterization of the surface intermediates during the initial stages of the deposition processes. The SPECIES beamline and the ALD cell provide a unique experimental platform for obtaining new information on the surface chemistry during ALD half-cycles at high temporal resolution. Such information is valuable for understanding the ALD reaction mechanisms and crucial in further developing and improving ALD processes. We demonstrate the capabilities of the setup by studying the deposition of TiO₂ on a SiO₂ surface by using titanium(IV) tetraisopropoxide and water as precursors. Multiple core levels and the valence band of the substrate surface were followed during the film deposition using ambient pressure XPS.

An experimental approach is described in which well-defined perturbations of the gas feed into an Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS) cell are fully synchronized with the time-resolved x-ray photoelectron spectroscopy data acquisition. These experiments unlock new possibilities for investigating the properties of materials and chemical reactions mediated by their surfaces, such as those in heterogeneous catalysis, surface science, and coating/deposition applications. Implementation of this approach, which is termed perturbation-enhanced APXPS, at the SPECIES beamline of MAX IV Laboratory is discussed along with several experimental examples including individual pulses of N₂ gas over a Au foil, a multi-pulse titration of oxygen vacancies in a pre-reduced TiO₂ single crystal with O₂ gas, and a sequence of alternating precursor pulses for atomic layer deposition of TiO₂ on a silicon wafer substrate.

The purpose of this study was to evaluate the mechanical properties of nanocrystalline hydroxyapatite coating by tensile adhesion testing and scratch testing. The coating was manufactured on titanium substrate by converting atomic layer-deposited (ALD) calcium carbonate thin film in dilute phosphate solution. The tensile adhesion testing was performed with hydraulic testing device in accordance with ISO 4624 and ISO 16276-1. Scratch testing was done according to SFS-EN 13523-12 with spherical 10 µm scratching tip. Characterization of the samples was done with light and electron microscopy after which they were stained with alizarin red and the failure modes and loadings were analyzed. The highest obtained tensile adhesion value was 6.71 MPa produced with 4000 ALD cycles, converted to hydroxyapatite in alkaline solution, and annealed for 30 min in 700 °C. The annealing improved the adhesion values by approximately 0.8 MPa, but examining the samples with electron microscopy showed intact coating in both annealed and non-annealed samples. Samples produced with 4000 cycles performed better in testing than 2000 cycle samples, and better adhesion was also achieved with alkaline conversion solution compared to neutral solution.

Electroblowing was used to prepare ZnO and aluminum doped zinc oxide (AZO, 1–3 cation-% of Al) fibers. The as-blown fibers were calcined at 500 °C to obtain the target material. The average fiber diameters ranged from 240 ± 60 nm for ZnO fibers to 330 ± 80 nm for AZO with 3% Al. Smaller crystallite size was measured with x-ray diffraction for the Al doped fibers. Electroblowing was found out be an effective method to increase the fiber productivity over electrospinning and other methods reported in literature to prepare AZO fibers as a high production rate of 0.32 g/h was achieved. The ZnO and AZO fibers could be converted to zeolitic imidazole framework-8 [ZIF-8, zinc(2-methylimidazolate)₂] by a solvent free thermal treatment in an autoclave under 2-methylimidazole (HmIM) vapor at 150 and 200 °C while preserving the fibrous structure. The conversion process to ZIF-8 occurred faster at higher temperatures and on fibers with smaller crystallite size. Depending on the conversion treatment time either ZnO/ZIF-8 and AZO/ZIF-8 core/shell fibers or ZIF-8 fibers could be obtained. At best the prepared ZIF-8 fibers had a very high BET specific surface area of 1340 m²/g.

Lithium fluoride (LiF) is an important optical material with a low refractive index and a large band gap. In this study, thin films of LiF are deposited using atomic layer deposition (ALD). Lithd and TiF4 are used as precursors, and they produce crystalline LiF in the temperature range 250–350 °C. The films are studied with UV-Vis spectrometry, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and elastic recoil detection analysis (ERDA). Adhesion of the films is tested by a Scotch tape test. This ALD process results in LiF films with a growth rate of approximately 1 Å per cycle at 325 °C. According to ERDA measurements, the films are pure LiF with only small O, C, and H impurities.

This article explores the history of atomic layer deposition (ALD) and its relationship with the American Vacuum Society (AVS). The authors describe the origin and history of ALD science in the 1960s and 1970s. They also report on how the science and technology of ALD progressed through the 1990s and 2000s and continues today. This article focuses on how ALD developed within the AVS and continues to evolve through interactions made possible by the AVS, in particular, the annual International AVS ALD Conference. This conference benefits students, academics, researchers, and industry practitioners alike who seek to understand the fundamentals of self-limiting, alternating binary surface reactions, and how they can be applied to form functional (and sometimes profitable) thin film materials. The flexible structure of the AVS allowed the AVS to quickly organize the ALD community and create a primary conference home. Many new research areas have grown out of the original concepts of "Atomic Layer Epitaxy" and "Molecular Layering," and some of them are described in this article. The people and research in the ALD field continue to evolve, and the AVS ALD Conference is a primary example of how the AVS can help a field expand and flourish.