Search results for "Al2O3"
showing 10 items of 18 documents
A First-Principles Study of the Ag/a-Al2O3(0001) Interface
2001
Ab initio simulations of the Ag/a-Al2O3(0001) interface have been performed for periodic slab models. We have considered Al- and O-terminated corundum surfaces, low and high substrate coverages by silver, as well as the two preferred Ag adsorption sites. The two different terminations give rise to qualitatively different results: silver physisorption on the Al-terminated substrate and chemisorption on O-terminated one. The latter could be treated as a possible model for the defective Al-terminated substrate, where the outermost aluminium ions are removed (completely or partly). This makes O-terminated surface highly reactive towards a deposited metal, in order to restore initial corundum st…
A liquid alkoxide precursor for the atomic layer deposition of aluminum oxide films
2020
For large-scale atomic layer deposition (ALD) of alumina, the most commonly used alkyl precursor trimethylaluminum poses safety issues due to its pyrophoric nature. In this work, the authors have investigated a liquid alkoxide, aluminum tri-sec-butoxide (ATSB), as a precursor for ALD deposition of alumina. ATSB is thermally stable and the liquid nature facilitates handling in a bubbler and potentially enables liquid injection toward upscaling. Both thermal and plasma enhanced ALD processes are investigated in a vacuum type reactor by using water, oxygen plasma, and water plasma as coreactants. All processes achieved ALD deposition at a growth rate of 1-1.4 angstrom/cycle for substrate tempe…
Thermal annealing and transformation of dimer F centers in neutron-irradiated Al2O3 single crystals
2020
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. In addition, the research leading to these results has received funding from the Estonian Research Council grant (PUT PRG619).
Ozone-Based Atomic Layer Deposition of Al2O3 from Dimethylaluminum Chloride and Its Impact on Silicon Surface Passivation
2017
Dimethylaluminum chloride (DMACl) as an aluminum source has shown promising potential to replace more expensive and commonly used trimethylaluminum in the semiconductor industry for atomic layer deposited (ALD) thin films. Here, the Al2O3 DMACl-process is modified by replacing the common ALD oxidant, water, by ozone that offers several benefits including shorter purge time, layer-by-layer growth, and improved film adhesion. It is shown that the introduction of the ozone instead of water increases carbon and chlorine content in the Al2O3, while long ozone pulses increase the amount of interfacial hydrogen at silicon surface. These are found to be beneficial effects regarding the surface pass…
Kinetics of the electronic center annealing in Al2O3 crystals
2018
Authors are greatly indebted to A. Ch. Lushchik, V. Kortov, M. Izerrouken and R.Vila for stimulating discussions. This work has been carried out within the framework of the Eurofusion Consortium and has received funding from the Euroatom research and training programme 2014–2018 under grant agreement No 633053 . The views and opinions expressed herein do not necessarily reflect those of the European Commission. The calculations were performed using facilities of the Stuttgart Supercomputer Center (project DEFTD 12939 ).
The corrosion and tribocorrosion resistance of PEO composite coatings containing α-Al2O3 particles on 7075 Al alloy
2018
Abstract Plasma electrolytic oxidation (PEO) of 7075 Al alloy was carried out in silicate base electrolyte containing 200 nm diameter α-Al2O3 particles for producing composite coatings. The process was performed under a soft-sparking regime using a pulsed bipolar signal with several concentrations of α-Al2O3 particles. It was found that the incorporation of α-Al2O3 particles into the coating did not significantly alter the thickness and roughness of the coating. However, the α-Al2O3 particles were detected on surface of the composite coatings. Corrosion tests showed significant improvement in corrosion performance of the composite coatings due to the efficient pore blocking provided by α-Al…
Effect of ozone concentration on silicon surface passivation by atomic layer deposited Al2O3
2015
Abstract We study the impact of ozone-based Al2O3 Atomic Layer Deposition (ALD) on the surface passivation quality of crystalline silicon. We show that the passivation quality strongly depends on the ozone concentration: the higher ozone concentration results in lower interface defect density and thereby improved passivation. In contrast to previous studies, our results reveal that too high interface hydrogen content can be detrimental to the passivation. The interface hydrogen concentration can be optimized by the ozone-based process; however, the use of pure ozone increases the harmful carbon concentration in the film. Here we demonstrate that low carbon and optimal hydrogen concentration…
Re-Evaluation of Chromium Doped Alumina for Dosimetric Applications
2021
Financial support provided by Scientific Research “Luminescence Mechanisms and Dosimeter Properties in Prospective Nitrides and Oxides Using TL and OSL Methods” LZP FLPP No. LZP-2018/1-0361 implemented at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. The Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART².
Simulations on the mechanism of CNT bundle growth upon smooth and nanostructured Ni as well as θ-Al2O3 catalysts
2011
Abstract In the current study, we have performed ab initio DFT calculations on the gradually growing 2D periodic models of capped single-wall carbon nanotubes (SW CNTs) upon their perpendicular junctions with the Ni(111) substrate, in order to understand the peculiarities of the initial stage of their growth on either smooth or nanostructured catalytic particles. Appearance of the adsorbed carbon atoms upon the substrate follows from the dissociation of CVD hydrocarbon molecules, e.g., CH4: (CH4)ads → (CH)ads+3Hads and (CH)ads → Cads+Hads. (Since the effective growth of CNTs upon Ni nanoparticles occur inside the nanopores of amorphous alumina, we have also simulated analogous surface react…
Temperature and time dependent electron trapping in Al2O3 thin films onto AlGaN/GaN heterostructures
2022
In this article, the charge trapping phenomena in Al2O3 thin films grown by atomic layer deposition (ALD) on AlGaN/GaN heterostructures have been studied by time-dependent capacitance–voltage (C-V) measurements as a function of temperature. In particular, monitoring the transient of the capacitance enabled us to estimate the maximum depth of the insulating layer interested by the negative charge trapping effect under our bias stress conditions and to determine a charge traps density in the bulk Al2O3 in the order of 3 × 1019 cm−3. A temperature dependent C-V analysis up to 150 °C demonstrated the presence of two competitive mechanisms that rule the electron capture and emission in the Al2O3…