Mobile setup for synchrotron based in situ characterization during thermal and plasma-enhanced atomic layer deposition

We report the design of a mobile setup for synchrotron based in situ studies during atomic layer processing. The system was designed to facilitate in situ grazing incidence small angle x-ray scattering (GISAXS), x-ray fluorescence (XRF), and x-ray absorption spectroscopy measurements at synchrotron facilities. The setup consists of a compact high vacuum pump-type reactor for atomic layer deposition (ALD). The presence of a remote radio frequency plasma source enables in situ experiments during both thermal as well as plasma-enhanced ALD. The system has been successfully installed at different beam line end stations at the European Synchrotron Radiation Facility and SOLEIL synchrotrons. Examples are discussed of in situ GISAXS and XRF measurements during thermal and plasma-enhanced ALD growth of ruthenium from RuO4 (ToRuS™, Air Liquide) and H2 or H2 plasma, providing insights in the nucleation behavior of these processes

Molecular layer deposition of "magnesicone", a magnesium-based hybrid material

Molecular layer deposition (MLD) offers the deposition of ultrathin and conformal organic or hybrid films which have a wide range of applications. However, some critical potential applications require a very specific set of properties. For application as desiccant layers in water barrier films, for example, the films need to exhibit water uptake and swelling and be overcoatable. For application as a backbone for a solid composite electrolyte for lithium ions on the other hand, the films need to be stable against lithium and need to be transformable from a hybrid MLD film to a porous metal oxide film. Magnesium-based MLD films, called "magnesicone", are promising on both these aspects, and thus, an MLD process is developed using Mg(MeCp)(2) as a metal source and ethylene glycol (EG) or glycerol (GL) as organic reactants. Saturated growth could be achieved at 2 to 3 angstrom/cycle in a wide temperature window from 100 to 250 degrees C. The resulting magnesicone films react with ambient air and exhibit water uptake, which is in the case of the GL-based films associated with swelling (up to 10%) and in the case of EG-based magnesicone with Mg(CO)(3) formation, and are overcoatable with an ALD of Al2O3. Furthermore, by carefully tuning the annealing rate, the EG-grown films can be made porous at 350 degrees C. Hence, these functional tests demonstrate the potential of magnesicone films as reactive barrier layers and as the porous backbone of lithium ion composite solid electrolytes, making it a promising material for future applications

Atomic layer deposition of localised boron- and hydrogen-doped aluminium oxide using trimethyl borate as a dopant precursor

Atomic layer deposition (ALD) of boron-containing films has been mainly studied for use in 2D materials and for B-doping of Si. Furthermore, lithium-containing borates show great promise as solid electrolyte coatings for enhanced energy storage. In this work, we examine trimethyl borate (TMB) and triethyl borate (TEB) in combination with O2 plasma as precursors for ALD of B-containing films, targeting the growth of B2O3. It is found that films grown from TEB contain no boron. Further work with TMB as a boron-containing precursor showed promising initial growth on a SiO2 or Al2O3 surface, but a rapid decrease of the growth rate during subsequent ALD cycles indicating surface inhibition during continued growth. DFT cluster calculations in combination with in-situ FTIR demonstrated that because of its weak Lewis acidity, the TMB molecule is found to adsorb via hydrogen-bonding to B-OH covered surfaces, without elimination of ligands, so that it is ubsequently removed in the plasmapulse and does not contribute to growth. The growth could be maintained in a mixedprocess, by reactivating the surface through single exposures to trimethyl aluminum(TMA) and oxygen plasma and thus resetting the surface to Al-OH, on which TMB chemisorption is energetically more favourable. Surprisingly, this process did not result in B2O3 (or Al-doped B2O3) films, but instead in B- and H-doped Al2O3 films. Moreover, rather than uniform boron doping, the Al2O3 films grown from this process contain a large amount of hydrogen, up to 17At% under certain processing conditions, and displayed non-uniform depth distributions of boron and hydrogen with a degree of control over the doping distribution based on the deposition conditions. Finally, the mechanism for the atypical growth mode is proposed based on in-situ FTIR and ellipsometry measurements and density functional theory calculations, and was attributed to sub-surface reactions of the TMA with the B-OH films grown by TMB-O2 plasma.This makes the process an interesting, albeit atypical, ALD process that allows for a quasi-continuous tuning of the B-concentration in the top region of high-purity Al2O3 films.peerReviewe

Effect of thermal annealing and chemical treatments on secondary electron emission properties of atomic layer deposited MgO

This study reports on the secondary electron emission (SEE) performance of atomic layer deposited MgO films, with thicknesses in the range from 5 to 25 nm, for the application in the Timed Photon Counter. In this novel, photodetector MgO is utilized as a material for the fabrication of ultrathin transmission dynodes (tynodes). Two different types of PECVD silicon oxide films are applied on top of MgO, in order to protect it against etching steps in the fabrication of tynodes and also as a prevention against aging. Applicability of these two materials as capping films is evaluated in terms of achieved secondary electron yield (SEY) of MgO after their removal. Emission of secondary electrons is known to depend on numerous physical and chemical properties of the material, such as surface roughness and chemical composition. On that account, morphological and structural properties of modified MgO are determined by atomic force microscope and x-ray photoelectron spectrometer and linked to the changes in SEE behavior. The authors demonstrate that the application of a suitable capping layer followed by its removal provides an SEY of 6.6, as opposed to the value of 4.8 recorded from the as-deposited MgO film. Furthermore, in a following experiment, they showed that annealing of MgO films at high temperatures (up to 1100 °C) significantly improved the secondary electron emission, elevating the SEY to 7.2.</p

Effect of thermal annealing and chemical treatments on secondary electron emission properties of atomic layer deposited MgO

This study reports on the secondary electron emission (SEE) performance of atomic layer deposited MgO films, with thicknesses in the range from 5 to 25 nm, for the application in the Timed Photon Counter. In this novel, photodetector MgO is utilized as a material for the fabrication of ultrathin transmission dynodes (tynodes). Two different types of PECVD silicon oxide films are applied on top of MgO, in order to protect it against etching steps in the fabrication of tynodes and also as a prevention against aging. Applicability of these two materials as capping films is evaluated in terms of achieved secondary electron yield (SEY) of MgO after their removal. Emission of secondary electrons is known to depend on numerous physical and chemical properties of the material, such as surface roughness and chemical composition. On that account, morphological and structural properties of modified MgO are determined by atomic force microscope and x-ray photoelectron spectrometer and linked to the changes in SEE behavior. The authors demonstrate that the application of a suitable capping layer followed by its removal provides an SEY of 6.6, as opposed to the value of 4.8 recorded from the as-deposited MgO film. Furthermore, in a following experiment, they showed that annealing of MgO films at high temperatures (up to 1100 °C) significantly improved the secondary electron emission, elevating the SEY to 7.2.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.EKL ProcessingElectronic Components, Technology and Material

Chemical and structural configuration of Pt doped metal oxide thin films prepared by atomic layer deposition

Pt-doped semiconducting metal oxides and Pt metal clusters embedded in an oxide matrix are of interest for applications such as catalysis and gas sensing, energy storage, and memory devices. Accurate tuning of the dopant level is crucial for adjusting the properties of these materials. Here, a novel atomic layer deposition (ALD)-based method for doping Pt into In2O3 specifically, and metals in metal oxides in general, is demonstrated. This approach combines alternating exposures of Pt and In2O3 ALD processes in a single "supercycle" followed by supercycle repetition leading to multilayered nanocomposites. The atomic-level control of ALD and its conformal nature make the method suitable for accurate dopant control even on high-surface-area supports. The oxidation state, local structural environment, and crystalline phase of the embedded Pt dopants were obtained by means of X-ray characterization methods and high-angle annular dark-field scanning transmission electron microscopy. In addition, this approach allows characterization of the nucleation stages of metal ALD processes by stacking those states multiple times in an oxide matrix. Regardless of experimental conditions, a few Pt ALD cycles lead to the formation of oxidized Pt species due to their highly dispersed nature, as proven by X-ray absorption spectroscopy. Grazing-incidence small-angle X-ray scattering and high-resolution scanning transmission electron microscopy, combined with energy-dispersive X-ray spectroscopy, show that Pt is evenly distributed in the In2O3 matrix without the formation of clusters. For a larger number of Pt ALD cycles, typically >10, the oxidation state gradually evolves toward fully metallic, and metallic Pt clusters are obtained within the In2O3 matrix. This work reveals how tuning of the ALD supercycle approach for Pt doping allows controlled engineering of the Pt compositional and structural configurations within a metal oxide matrix