Atomic Layer Deposition

Physical instability remains a major concern with amorphous solid dispersions (ASDs). In addition to bulk crystallization inhibition, another potential strategy to improve the physical stability of ASDs is surface engineering. However, coating processes are extremely challenging for ASD microparticles. Herein, we describe for the first time the application of atomic layer coating (ALC), a solvent-free technique, to deposit a pinhole-free, ultra-thin film of aluminum oxide onto the surface of spray-dried ASD particles containing high drug loadings of ezetimibe with hydroxypropyl methylcellulose acetate succinate. ALC affords excellent control over the thickness, uniformity and conformality of the coating at the atomic scale. The freshly prepared coated ASD powders exhibited less agglomeration, a lower hygroscopicity, as well as improved wettability, flowability and compressibility compared to the uncoated samples. Under accelerated storage conditions, crystallization was detected in the uncoated 50% and 70% drug loading ASDs after only a few days, whereas the coated samples showed no evidence of physical instability for two years. Consequently, there was a dramatic decrease in the drug release from the uncoated ASDs during storage, while little change was observed for the coated samples. Using ALC for surface nanocoating of ASD paves the way for the development of higher drug loading ASD without compromising physical stability, thereby reducing the pill burden.

Many fields including the aerospace industry have shown increased interest in the use of plastics to lower the mass of systems. However, the use of plastics in space can be challenging for a number of reasons. Ultraviolet radiation, atomic oxygen and other phenomena specifically associated with space cause the degradation of polymers. Here we show a path towards creation of space-grade components by combining additive manufacturing (AM) and atomic layer deposition (ALD). Our method produced ALD Al2O3 coated thermoplastic parts, suitable for space applications. The highlight of this work is a significant reduction in outgassing, demonstrated using residual gas analyzer (RGA) sampling. Compared to uncoated parts, the ALD-Al2O3 coating decreased the outgassing of polyether ether ketone (PEEK), acrylonitrile butadiene styrene (ABS), polycarbonate (PC) and nanodiamond-doped polylactide (ND-PLA) by 46%, 49%, 58% and 65% respectively. The manufacturing method used in this work enables the use of topology optimization already in the early concept creation phase. The method is ideally suited for spacecraft applications, where the volume and mass of parts is critical, and could also be adapted for in-space manufacturing.

In this paper, we report the plasma-enhanced atomic layer deposition (PEALD) of TiO 2 and TiO 2 /Al 2 O 3 nanolaminate films on p-Si(100) to fabricate metal-oxide-semiconductor (MOS) capacitors. In the PEALD process, we used titanium tetraisopropoxide (TTIP) as a titanium precursor, trimethyl aluminum (TMA) as an aluminum precursor and O 2 plasma as an oxidant, keeping the process temperature at 250 • C. The effects of PEALD process parameters, such as RF power, substrate exposure mode (direct or remote plasma exposure) and Al 2 O 3 partial-monolayer insertion (generating a nanolaminate structure) on the physical and chemical properties of the TiO 2 films were investigated by Rutherford backscattering spectroscopy (RBS), Raman spectroscopy, grazing incidence X-ray diffraction (GIXRD), and field emission scanning electron microscopy (FESEM) techniques. The MOS capacitor structures were fabricated by evaporation of Al gates through mechanical mask on PEALD TiO 2 thin film, followed by evaporation of an Al layer on the back side of the Si substrate. The capacitors were characterized by current density-voltage (J-V), capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. Our results indicate that RF power and exposure mode promoted significant modifications on the characteristics of the PEALD TiO 2 films, while the insertion of Al 2 O 3 partial monolayers allows the synthesis of TiO 2 /Al 2 O 3 nanolaminate with well-spaced crystalline TiO 2 grains in an amorphous structure. The electrical characterization of the MOS structures evidenced a significant leakage current in the accumulation region in the PEALD TiO 2 films, which could be reduced by the addition of partial-monolayers of Al 2 O 3 in the bulk of TiO 2 films or by reducing RF power.

We investigated the effectiveness of SiN and SiON barrier layer in controlling the interfacial reaction between Atomic Layer Deposited (ALD) HfO2 film and the Si substrate. The HfO2 film was found to form silicate and silicide at the interface with Si after 5 min post deposition annealing in Ar at 800 and 1000 °C as observed by scanning transmission electron microscopy/electron energy

Atomic Layer Deposition (ALD) method has been used to synthesis
nanocoatings thin films of Alumina, Titania, and Alumina/Titania multilayer on stainless steel AISI 316L at 250 °C deposition
temperatures for the medical applications. SEMand EDX have been used to characterize the morphology of the films and the element
analysis of the alloys and the thin films respectively. Open circuit potential, potentiostatic polarization (Tafel extrapolation) and cyclic polarization methods have been used to study the corrosion resistance of the films in Simulation Body Fluid (SBF) at 37 ± 1 ºC. Immersion test in SBF for 2weeks at 37± 1 ºC has been used to determine
the biocompatibility of the films. Numbers of colonies and diffusion zone methods have been used after cultured non-pathogeni E-coli bacteria to demonstrate the bioactivity (toxicity effects) of the thin films. The SEM morphology observations show different particles shape and size of the Alumina (nanotubes shape around 10-20 nm in size) and
Titania films (cauliflower particles shape around 20-50nm in size). The results also show that the corrosion resistance can be effectively enhanced by thin films, multilayer proved to be more corrosion protection than single layers, and Alumina has better corrosion
resistance than Titania.

Aluminum-doped p-type (Al-p+) silicon emitters fabricated by means of screen-printing and firing are effectively passivated by plasma-enhanced chemical-vapor deposited (PECVD) amorphous silicon (a-Si) and atomic-layer-deposited (ALD) aluminum oxide (Al2O3) as well as Al2O3/SiNx stacks, where the silicon nitride (SiNx) layer is deposited by PECVD. While the a-Si passivation of the Al-p+ emitter results in an emitter saturation current density J0e of 246 fA/cm2, the Al2O3/SiNx double layers result in emitter saturation current densities as low as 160 fA/cm2, which is the lowest J0e reported so far for screen-printed Al-doped p+ emitters. Moreover, the Al2O3 as well as the Al2O3/SiNx stacks show an excellent stability during firing in a conveyor belt furnace at 900°C. We implement our newly developed passivated Al-p+ emitter into an n+np+ solar cell structure, the so-called ALU+ cell. An independently confirmed conversion efficiency of 20% is achieved on an aperture cell area of 4 cm2, clearly demonstrating the high-efficiency potential of our ALU+ cell concept.

Nanoscale films of tungsten nitride (WN) were deposited as environmental barrier coatings (EBCs) by particle atomic layer deposition (ALD) on zirconia nanoparticles and yttria stabilized zirconia micropowders. Hydrogen diffusion in tungsten (W) was investigated computationally using density functional theory and experimentally using differential thermal analysis of the ALD samples in hydrogen at temperatures > 1000°C. Reaction of hydrogen with the underlying material was delayed but not eliminated by the ALD film, consistent with the low computationally predicted hydrogen diffusion barrier in bulk W of 0.19 eV. This is the first study of WN ALD films as EBCs for hydrogen above 1000°C.

In this paper, theoretical and experimental approaches were used to evaluate the impact of the precursor's pulse time on the growth per cycle and the crystallinity quality of atomic layer deposited TiO 2 thin films on Si(100) and FTO substrates. We employ a general model that can be applied to both metal and oxidant precursors, based on the Maxwell-Boltzmann velocity distribution from which the molecular flux of gases that collide with the substrate is deduced to adjust the experimental characteristics of growth per cycle vs. pulse time. This model allowed us to adjust the growth per cycle of TiO 2 films produced by thermal atomic layer deposition and by plasma-enhanced atomic layer deposition under different deposition parameters and substrates. The influence of growth per cycle on the chemical and structural properties of TiO 2 thin films was evaluated by Rutherford backscattering spectroscopy, grazing incidence x-ray diffraction, and ellipsometry techniques. In thermal mode, using H 2 O as an oxidant precursor, the stoichiometry of TiO x films has an x value of 1.98 from the growth per cycle saturated regardless of the metal precursor or substrate used. Using O 2 plasma, a super-stoichiometric film with x values from 2.02 to 2.30 was obtained. In thermal mode, the growth per cycle saturated and film thickness are, on average, 40% higher for TiCl 4 compared to TTIP precursor. Using O 2 plasma, the growth per cycle saturated is approximately twice as high as the thermal mode using the TTIP precursor. For both atomic layer deposition modes, the degree of crystallinity showed values of 50-80% for TiCl 4 in the temperature range of 250-350 • C. For TTIP, it was below 40% in thermal mode and between 80 and 95% in plasma mode (250 • C). It was observed that the reaction rate, the diffusion coefficient, and the molecular flux are inversely proportional to the temperature. These results provide evidence that the crystallinity and epitaxial quality of the TiO 2 film are higher for TTIP using O 2 plasma. However, we verified that

Atomic Layer Deposition (ALD) has been used to deposit Titanium Dioxide (TiO2) and Aluminum Oxide (Al2O3) thin film on stainless steel and Si-wafer (100) substrates. For TiO2, Tetrakis (dimethylamido) titanium (TDMAT) {Ti (NMe2)4} was used. Also for Al2O3 , Trimethylaluminum (TMA) {Al (CH3)3 } was used. H2O as precursors used for two of them and at 250 °C deposition temperatures. Growth rates of thin film, thin film properties (including thickness, refractive index, and reflectivity) and surface roughness were determined using Spectroscopic Ellipsometry and Optical Profillometer. The results showed good quality films without micro crack, good thin films properties and non-linear growth rates were observed from the results data. Al2O3 ALD film exhibited low surface roughness values, low growth rates diversion and the nearest film thickness compared with TiO2 ALD film.

Introduction: Silver, prized throughout history for its luster and shine, develops a black Ag 2 S tarnish layer that is aesthetically displeasing when exposed to atmospheric pollutants. Tarnishing, and subsequent polishing, leads to irreversible material loss and object damage. Currently, nitrocellulose coatings are often used to prevent silver from tarnishing, however non‑uniform coatings and degradation over time limit their effectiveness. Atomic layer deposi‑ tion (ALD) has been explored as a new method for creating dense, uniform, and conformal coatings on 3‑dimensional (3D) objects that are more effective than nitrocellulose in preventing silver from tarnishing. Results: To create high quality ALD coatings on 3D objects, slowing down the ALD process is critical to ensure proper precursor exposure. Non‑ideal deposition of organo‑oxy‑metallic compounds can occur with fast deposition rates that do not allow sufficient flow around 3D objects. The coatings can be removed by dissolving the Al 2 O 3 ALD films in aqueous NaOH. Thicker ALD films prevent defects from occurring on non‑ideal surfaces and effectively pre‑ vent silver objects from tarnishing under ambient aging conditions. Conclusion: Thick ALD films, deposited with sufficiently long precursor pulse and purge times, may be effective in preventing complex, 3D non‑mixed media silver cultural heritage objects from tarnishing.

• TiO 2 thin films with brookite phase successfully deposited on Si(111) using ALD. • Correlated Structural and optical properties perceived and studied. • Reduction of refractive index observed for films with ultra-small thicknesses. In this paper, titanium dioxide (TiO 2) thin films, deposited on single crystal Si (111) substrates under different temperature conditions by Atomic Layer Deposition (ALD), have been systematically studied by X-ray diffrac-tion, photoluminescence spectroscopy and spectroscopic ellipsometry methods. X-ray diffraction analysis showed that the prepared films have a polycrystalline brookite phase over a growth temperature range of (150-300 °C). Increasing the growth temperature resulted in systematic increase of texturing the polycrystalline grains along the (200) direction, with the film at 300 °C having the highest textur along the (200) direction. This was accompanied by improved photoluminescence of the TiO 2 films with the increasing the growth temperature. The improved crystallinity at higher temperatures was also reflected by higher refractive indices, which were deduced from spectroscopic ellipsometry measurements carried out on the grown films.

Carbothermic reduction in the chemistry of metal extraction (MO(s) + C(s) → M(s) + CO(g)) using carbon as a sacrificial agent has been used to smelt metals from diverse oxide ores since ancient times. Here, we paid attention to another aspect of the carbothermic reduction to prepare activated carbon textile for high rate-performance supercapacitors. On the basis of thermodynamic reducibility of metal oxides reported by Ellingham, we employed not carbon, but metal oxide as a sacrificial agent in order to prepare activated carbon textile. We conformally coated ZnO on bare cotton textile using atomic layer deposition (ALD), followed by pyrolysis at high temperature (C(s) + ZnO(s) → C’(s) + Zn(g) + CO(g)). We figured out that it leads to concurrent carbonization and activation in a chemical as well as mechanical way. Particularly, the combined effects of mechanical buckling and fracture occurred between ZnO and cotton were turned out to play an important role in carbonizing and activating cotton textile, thereby significantly increasing surface area (nearly 10 times) compared with the cotton textile prepared without ZnO. The carbon textiles prepared by carbothermic reduction showed impressive combination properties of high power and energy densities (over 20 times increase) together with high cyclic stability.

We report highly selective emitters based on high-aspect ratio 2D photonic crystals (PhCs) fabricated on large area (2 inch diameter) polycrystalline tantalum substrates, suitable for high-temperature operation. As an example we present an optimized design for a selective emitter with a cut-off wavelength of 2μm, matched to the bandgap of an InGaAs PV cell, achieving a predicted spectral selectivity of 56.6% at 1200K. We present a fabrication route for these tantalum PhCs, based on standard microfabrication processes including deep reactive ion etch of tantalum by an SF6 based Bosch process, achieving high-aspect ratio cavities (< 8:1). Interference lithography was used to facilitate large area fabrication, maintaining both fabrication precision and uniformity, with a cavity diameter variation of less than 2% across the substrate. The fabricated tantalum PhCs exhibit strong enhancement of the emittance at wavelengths below cut-off wavelength, approaching that of blackbody, and a ...

Aluminium oxide and titanium oxide films were deposited using the Atomic Layer Deposition method on n-type 4H SiC and p-type Si {001} substrates, with doping 6×1015cm-3 and 2×1016cm-3, respectively, and on 1.2 kV PiN 4H SiC diodes for passivation studies. The Al2O3 and SiC interface was characterised for the existence of an effective negative charge with a density of 1×1012-2×1012 cm-2. The dielectric constant of Al2O3 as determined from capacitance-voltage data was about 8.3. The maximum electric field supported by the Al2O3 film was up to 7.5 MV/cm and 8.4 MV/cm on SiC and Si, respectively.