Annealing of thin 'Tincone' films, a tin-based hybrid material deposited by molecular layer deposition, in reducing, inert, and oxidizing atmospheres

Molecular layer deposition of hybrid organic-inorganic thin films called "tincones" is achieved using tetrakisdimethylaminotin as the metal precursor and glycerol (GL) as the organic reactant. The GL-based process displays linear growth and self-limiting surface reactions in a broad temperature window ranging from 75 to 200 degrees C. At higher temperatures, no film growth is possible. The growth per cycle decreases rapidly with increasing temperature from 1.3 angstrom(with numbers) at 75 degrees C to less than 0.1 angstrom at 200 degrees C. The films are observed to be smooth with scanning electron microscopy and atomic force microscopy. The hybrid organic-inorganic nature of the films is visible in both infrared spectroscopy and x-ray photoelectron spectroscopy. As deposited tincone films are annealed in reducing (H-2), inert (He), or oxidizing (O-2) atmospheres. In situ x-ray diffraction is employed to study the crystallization of the films during annealing. Tincone films annealed in reducing or inert atmosphere crystallize into a tetragonal SnO phase at 388 and 410 degrees C, respectively. These temperatures are lower than the crystallization temperature of 480 degrees C for atomic layer deposition (ALD) tin oxide films annealed in H-2. Tincone films annealed in oxygen crystallize into an SnO2 phase at a temperature of 523 degrees C, which is similar to the crystallization temperature for ALD tin oxide films annealed in He or O-2. This reduced temperature for crystallization into SnO for the tincone films is interesting since SnO is one of the few metal oxides known as a p-type semiconductor material

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

In situ study of the thermal stability of supported Pt nanoparticles and their stabilization via atomic layer deposition overcoating

Downscaling of supported Pt structures to the nanoscale is motivated by the augmentation of the catalytic activity and selectivity, which depend on the particle size, shape and coverage. Harsh thermal and chemical conditions generally required for catalytic applications entail an undesirable particle coarsening, and consequently limit the catalyst lifetime. Herein we report an in situ synchrotron study on the stability of supported Pt nanoparticles and their stabilization using atomic layer deposition (ALD) as the stabilizing methodology against particle coarsening. Pt nanoparticles were thermally annealed up to 850 degrees C in an oxidizing environment while recording in situ synchrotron grazing incidence small angle X-ray scattering (GISAXS) 2D patterns, thereby obtaining continuous information about the particle radius evolution. Al2O3 overcoat as a protective capping layer against coarsening via ALD was investigated. In situ data proved that only 1 cycle of Al2O3 ALD caused an augmentation of the onset temperature for particle coarsening. Moreover, the results showed a dependence of the required overcoat thickness on the initial particle size and distribution, being more efficient (i.e. requiring lower thicknesses) when isolated particles are present on the sample surface. The Pt surface accessibility, which is decisive in catalytic applications, was analyzed using the low energy ion scattering (LEIS) technique, revealing a larger Pt surface accessibility for a sample with Al2O3 overcoat than for a sample without a protective layer after a long-term isothermal annealing

Molecular layer deposition of 'vanadicone', a vanadium-based hybrid material, as an electrode for lithium-ion batteries

Molecular layer deposition (MLD) of hybrid organic-inorganic thin films called "vanadicones" was investigated using tetrakisethylmethylaminovanadium (TEMAV) as the metal precursor and glycerol (GL) or ethylene glycol (EG) as the organic reactant. Linear and continued growth could only be achieved with GL as the organic reactant. The TEMAV/GL process displayed self-limiting reactions for both precursor and reactant pulses in the temperature range from 80 degrees C to 180 degrees C, with growth rates of 1.2 to 0.5 A per cycle, respectively. Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed the hybrid nature of the films. From X-ray reflectivity, the density was estimated at 2.6 g cm(-3). A series of 21 nm vanadicone films were subjected to annealing under oxidizing (air) or inert (He) atmospheres at 500 degrees C. During annealing in air, the film crystallized to the V2O5 phase and all carbon was removed from the film. The films annealed in helium remained amorphous and retained most of their carbon content. Electrochemical measurements revealed lithium-ion activity during cyclic voltammetry in all treated films, while the as deposited film was inactive. In the 2.9 to 3.5 V vs. Li+/Li potential region, no improvement over the V2O5 reference was observed. However, the helium annealed samples outperformed V2O5 in terms of capacity, rate performance and cyclability when charged and discharged in the 1.0 to 3.5 V vs. Li+/Li region. This result enables the application of VxOy-based hybrid electrodes in a wider potential range without sacrificing the stability and performance

The transformation behaviour of “alucones”, deposited by molecular layer deposition, in nanoporous Al2O3 layers

International audienc

Molecular layer deposition of 'titanicone', a titanium-based hybrid material, as an electrode for lithium-ion batteries

Molecular layer deposition (MLD) of hybrid organic-inorganic thin films called "titanicones" was achieved using tetrakisdimethylaminotitanium (TDMAT) and glycerol (GL) or ethylene glycol (EG) as precursors. For EG, in situ ellipsometry revealed that the film growth initiates, but terminates after only 5 to 10 cycles, probably because both hydroxyls react with the surface. GL has a third hydroxyl group, and in that case steady state growth could be achieved. The GL process displayed self-limiting reactions for both reactants in the temperature range from 80 degrees C to 160 degrees C, with growth rates of 0.9 to 0.2 angstrom per cycle, respectively. Infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the hybrid nature of the films, with a carbon atomic concentration of about 20%. From X-ray reflectivity, the density was estimated at 2.2 g cm(-3). A series of films was subjected to water etching and annealing under air or He atmosphere at 500 degrees C. The carbon content of the films was monitored with FTIR and XPS. Almost all carbon was removed from the air annealed and water treated films. The He annealed samples however retained their carbon content. Ellipsometric porosimetry (EP) showed 20% porosity in the water etched samples, but no porosity in the annealed samples. Electrochemical measurements revealed lithium ion activity during cyclic voltammetry in all treated films, while the as-deposited film was inactive. With increasing charge current, the He annealed samples outperformed amorphous and anatase TiO2 references in terms of capacity retention

Plasma-enhanced atomic layer deposition : correlating O2 plasma parameters and species to blister formation and conformal film growth

Plasma-enhanced atomic layer deposition has gained a lot of attraction over the past few years. A myriad of processes have been reported, several reviews have been written on this topic, and there is a lot of interest for industrial applications. Still, when developing new processes, often heuristic approaches are used, choosing plasma parameters that worked for earlier processes. This can result in suboptimal plasma process conditions. In order to rationally decide which parameters to use, we systematically studied an inductively coupled RF oxygen plasma source (13.56 MHz) for powers up to 300 W, a pressure range between 10(-4) and 10(-2 )mbar, and a flow range between 10 and 400 sccm. We discerned between chemically active "radical " species (atomic O and excited, metastable O-2) and ionic particles ( O-2(+), O+, O-2(-), and O-), which can have an additional physical effect to the film. Optical emission spectroscopy (OES) was used to study the generation of O-2(+) and atomic O in the plasma source region. It is shown that the concentration of plasma species increases in a linear way with the plasma power and that the atom-to-ion fraction increases with both the power and the gas flow. To study the effect of plasma species in the remote region, near the sample position, an electrostatic quadrupole analyzer was used to gauge fluxes of O-2+, O+, O-2(-), and O-. Even a moderate increase in pressure can drastically reduce the ion flux toward the substrate. The formation of bubbles or blisters in films can be linked to ion-induced compressive stress, and, hence, it can be mitigated by an increase in the gas pressure. Finally, Al2O3 was deposited in lateral high-aspect ratio structures to investigate the effect of plasma power and gas pressure on the partial pressure of radical species. Simulated profiles were fitted to experimental deposition profiles to estimate trends in the radical partial pressure, and a linear relationship between radical partial pressure and the power was found. This correlated with the density of atomic O species as observed in the OES measurements in the plasma source region. The methods presented in this work are also applicable to characterize other reactor geometries, plasma sources, and gas mixtures