Atomic Layer Deposition-Based Synthesis of Photoactive TiO2 Nanoparticle Chains by Using Carbon Nanotubes as Sacrificial Templates

Highly ordered and self supported anatase TiO2 nanoparticle chains were fabricated by calcining conformally TiO2 coated multi-walled carbon nanotubes (MWCNTs). During annealing, the thin tubular TiO2 coating that was deposited onto the MWCNTs by atomic layer deposition (ALD) was transformed into chains of TiO2 nanoparticles (~12 nm diameter) with an ultrahigh surface area (137 cm2 per cm2 of substrate), while at the same time the carbon from the MWCNTs was removed. Photocatalytic tests on the degradation of acetaldehyde proved that these forests of TiO2 nanoparticle chains are highly photo active under UV light because of their well crystallized anatase phase

Synthesis of a 3D network of Pt nanowires by atomic layer deposition on carbonaceous template

The formation of a 3D network composed of free standing and interconnected Pt nanowires is achieved by a two-step method, consisting of conformal deposition of Pt by atomic layer deposition (ALD) on a forest of carbon nanotubes and subsequent removal of the carbonaceous template. Detailed characterization of this novel 3D nanostructure was carried out by transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). These characterizations showed that this pure 3D nanostructure of platinum is self-supported and offers an enhancement of the electrochemically active surface area by a factor of 50

Electrodeposition of adherent submicron to micron thick manganese dioxide films with optimized current collector interface for 3D Li-ion electrodes

Three-dimensional (3D) configuration of high-performance energy storage devices has been the subject of ongoing investigations targeting their integration in autonomous microelectronic systems. In this study we demonstrate a route toward the realization of high capacity cathode material for 3D thin-film lithium-ion (Li-ion) batteries. Electrolytic manganese dioxide (EMD) film can be applied as a Li-ion intercalation electrode upon its conversion to lithium manganese dioxide (LiMn2O4 or LMO) by solid-state reaction. The main challenges of depositing thicker EMD film directly on the current collector often lay in achieving a good film adhesion and preventing oxidation of non-noble current collectors such as TiN, Ni. To improve the adhesion of the EMD films we modify the surface of the current collector by means of thin-film or seed layer coatings, which also prevent the oxidation of the underlying current collector substrate during the anodic deposition process. As a result submicron to micron thick EMD films with good adhesion were deposited on various current collectors. The acidity of the electrolyte solutions was varied depending on the type of the surface coating or current collector used. The mechanism of the EMD film growth and morphology on different substrates was examined. Compatibility of the proposed current collector interface modification for the electrodeposition of conformal thick EMD films on high-aspect ratio microstructures was demonstrated. A method of EMD film conversion to LMO at low-temperature on different substrates was shown as the path toward their application in 3D Li-ion batteries

Photocatalytic acetaldehyde oxidation in air using spacious TiO2 films prepared by atomic layer deposition on supported carbonaceous sacrificial templates

Supported carbon nanosheets and carbon nanotubes served as sacrificial templates for preparing spacious TiO2 photocatalytic thin films. Amorphous TiO2 was deposited conformally on the carbonaceous template material by atomic layer deposition (ALD). Upon calcination at 550{\deg}C, the carbon template was oxidatively removed and the as-deposited continuous amorphous TiO2 layers transformed into interlinked anatase nanoparticles with an overall morphology commensurate to the original template structure. The effect of type of template, number of ALD cycles and gas residence time of pollutant on the photocatalytic activity, as well as the stability of the photocatalytic performance of these thin films was investigated. The TiO2 films exhibited excellent photocatalytic activity towards photocatalytic degradation of acetaldehyde in air as a model reaction for photocatalytic indoor air pollution abatement. Optimized films outperformed a reference film of commercial PC500

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

Growth Mechanism of a Hybrid Structure Consisting of a Graphite Layer on Top of Vertical Carbon Nanotubes

Graphene and carbon nanotubes (CNTs) are both carbon-based materials with remarkable optical and electronic properties which, among others, may find applications as transparent electrodes or as interconnects in microchips, respectively. This work reports on the formation of a hybrid structure composed of a graphitic carbon layer on top of vertical CNT in a single deposition process. The mechanism of deposition is explained according to the thickness of catalyst used and the atypical growth conditions. Key factors dictating the hybrid growth are the film thickness and the time dynamic through which the catalyst film dewets and transforms into nanoparticles. The results support the similarities between chemical vapor deposition processes for graphene, graphite, and CNT

Integrated cleanroom process for the vapor-phase deposition of large-area zeolitic imidazolate framework thin films

Robust and scalable thin-film deposition methods are key to realize the potential of metal-organic frameworks (MOFs) in electronic devices. Here, we report the first integration of the chemical vapor deposition (CVD) of MOF coatings in a custom reactor within a cleanroom setting. As a test case, the MOF-CVD conditions for the zeolitic imidazolate framework-8 are optimized to enable smooth, pinhole-free, and uniform thin films on full 200 mm wafers under mild conditions. The single-chamber MOF-CVD process and the impact of the deposition parameters are elucidated via a combination of in situ monitoring and ex situ characterization. The resulting process guidelines will pave the way for new MOF-CVD formulations and a plethora of MOF-based devices