Atomic layer deposition (ALD) is a cyclic process which relies on sequential self-terminating reactions between gas phase precursor molecules and a solid surface. The self-limiting nature of the chemical reactions ensures precise film thickness control and excellent step coverage, even on 3D structures with large aspect ratios. At present, ALD is mainly used in the microelectronics industry, e.g. for growing gate oxides. The excellent conformality that can be achieved with ALD also renders it a promising candidate for coating porous structures, e.g. for functionalization of large surface area substrates for catalysis, fuel cells, batteries, supercapacitors, filtration devices, sensors, membranes etc. This tutorial review focuses on the application of ALD for catalyst design. Examples are discussed where ALD of TiO(2) is used for tailoring the interior surface of nanoporous films with pore sizes of 4-6 nm, resulting in photocatalytic activity. In still narrower pores, the ability to deposit chemical elements can be exploited to generate catalytic sites. In zeolites, ALD of aluminium species enables the generation of acid catalytic activity.

Atomic layer deposition (ALD) is an attractive film growth technique for a variety of modern technologies. The method relies on sequential self-terminating gasÀsolid reactions separated by evacuation steps, i.e. purging or pumping of the deposition chamber. 1,2 The self-limiting nature of the chemical reactions allows for a layer-by-layer type growth and ensures precise thickness control and excellent conformality on substrates with complex topologies, even at the nanometer scale. So far, ALD has mainly been used in the semiconductor industry, but its ability for conformal deposition of ultrathin films could impact a broad range of additional applications, such as catalysis, fuel cells, batteries, filtration devices, etc.In order to fully exploit the unique advantages of ALD, it is important to optimize the process sequence and to understand the underlying surface reactions. In recent literature, mainly in situ diagnostics have been used to obtain fundamental information about the growth kinetics of ultrathin films deposited by ALD. In situ techniques offer the ability to monitor film properties or reaction products while ALD growth is occurring. Techniques that are often used during ALD are spectroscopic ellipsometry (SE), 3 infrared spectroscopy, 4À8 quadrupole mass spectrometry, 8À12 and quartz crystal microbalance. 9,10,13 They provide information on the thickness and optical properties of the film, the chemical surface groups, the gaseous reaction products and the mass uptake during the different process steps.

A system is demonstrated that autonomously produces hydrogen gas using sunlight and outside air as the only inputs. Oxygen and hydrogen formation reactions occur on either side of a monolithic "solar membrane" inserted in a two-compartment photoelectrochemical cell. A surface film of Nafion (R) serves as a solid electrolyte. This proof of concept invites further development of air-based cells

Ammonia treatment of USY zeolite has led to a new hierarchical material. The local and global structural changes during the transformation have been monitored by XRD and by 1 H, 29 Si, and 27 Al solid-state NMR. A wealth of 1D and 2D NMR protocols were applied, including 1 H DQ-SQ, 27 Al MQMAS, 29 Si MAS and CPMAS as well as 1 H-29 Si HETCOR. The effects of aqueous ammonia treatment, different thermal post-treatments and rehydration were studied. An increasing loss of crystallinity was observed upon increasing duration of ammonia treatment. Under the experimental conditions a few percent of silica was lost into solution and no loss of aluminum was observed. But, increasing numbers of silanol groups were detected. The progressive transformation induces formation of mesopores, reduction of the fraction of the sample exhibiting Bragg crystallinity and apparition of a dense, amorphous aluminosilicate phase. The latter contains ammonium ions and strongly bound water which both are resistant to thermal decomposition up to 350 °C. After about 24 hours of treatment the zeolite fraction has been completely transformed into the amorphous phase. At intermediate stages a complexhierarchical material is obtained with mesopores and zeolitic micropores next to a dense amorphous aluminosilicate, containing ammonium ions, highly structured water and silanols nests.

Amorphous Ga2O3 thin films have been grown on SiO2/Si substrates by atomic layer deposition (ALD) using tris (2,2,6,6-tetramethyl-3,5-heptanedionato) gallium(III) [Ga(TMHD)(3)] as a gallium source and O-2 plasma as reactant. A constant growth rate of 0.1 angstrom per cycle was obtained in a broad temperature range starting from 100 to 400 degrees C. X-ray photoelectron spectroscopy (XPS) analysis revealed stoichiometric Ga2O3 thin films with no detectable carbon contamination. A double beam - double monochromator spectrophotometer was used to measure the transmittance of Ga2O3 thin films deposited on a quartz substrate and analysis of the adsorption edge yielded a band gap energy of 4.95 eV. The refractive index of the Ga2O3 films was determined from spectroscopic ellipsometry measurements and found to be 1.84 at a wavelength of 632.8 nm. Atomic force microscopic (AFM) analysis showed surface roughness values of 0.15 and 0.51 nm for films deposited at 200 and 400 degrees C, respectively. Finally, all the films could be crystallized into a monoclinic beta-Ga2O3 crystal structure by a post deposition annealing in He as indicated by X-ray diffraction (XRD) measurements

Ellipsometric porosimetry (EP) is a handy technique to characterize the porosity and pore size distribution of porous thin films with pore diameters in the range from below 1 nm up to 50 nm and for the characterization of porous low-k films especially. Atomic layer deposition (ALD) can be used to functionalize porous films and membranes, e.g., for the development of filtration and sensor devices and catalytic surfaces. In this work we report on the implementation of the EP technique onto an ALD reactor. This combination allowed us to employ EP for monitoring the modification of a porous thin film through ALD without removing the sample from the deposition setup. The potential of in situ EP for providing information about the effect of ALD coating on the accessible porosity, the pore radius distribution, the thickness, and mechanical properties of a porous film is demonstrated in the ALD of TiO(2) in a mesoporous silica film.

Portable, low cost and real-time gas sensors have a considerable potential in various biomedical and industrial applications. For such applications, nano-photonic gas sensors based on standard silicon fabrication technology offer attractive opportunities. Deposition of high surface area nano-porous coatings on silicon photonic sensors is a means to achieve selective, highly sensitive and multiplexed gas detection on an optical chip. Here we demonstrate selective and reversible ammonia gas detection with functionalized silicon-on-insulator optical micro-ring resonators. The micro-ring resonators are coated with acidic nano-porous aluminosilicate films for specific ammonia sensing, which results in a reversible response to NH 3 with selectivity relative to CO 2 . The ammonia detection limit is estimated at about 5 ppm. The detectors reach a steady response to NH 3 within 30 and return to their base level within 60 to 90 seconds. The work opens perspectives on development of nano-photonic sensors for real-time, non-invasive, low cost and light weight biomedical and industrial sensing applications. ©2012 Optical Society of America

Silver nitrate induces spontaneous room temperature transformation of ZIF-8 into a composite of ZnO nanorods embedded in a ZIF-8 matrix. This first example of reverse transformation of ZIF-8 into ZnO is a convenient method for generating fixed ZnO nanoparticles in powders as well as films and coatings. The fabricated ZnO nanorod@ZIF-8 is photocatalytically active.