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°C to 160°C, with growth rates of 0.9 to 0.2 Å 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°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.

Nanoporous alumina films can be synthesized from hybrid organic-inorganic "alucone" films deposited by molecular layer deposition (MLD) by wet etching in deionized water or calcination in air at 500 °C. This transformation process was systematically investigated for two alucone chemistries based on ethylene glycol (EG) and glycerol (GL). Ellipsometric porosimetry (EP) was used for the characterization of the porous alumina structures that are formed as a result of the treatments. Etching in deionized water transforms both EG- and GL-alucones into porous alumina with a porosity of about 40%, albeit with a different pore structure: cylindrical pores for EG-alucones and ink-bottle structures for GL-alucones. Calcination in air up to 500 °C only successfully transformed EG-alucones into porous alumina if the chosen heating and cooling rate was lower than 200 °C h-1. Below this ramp rate, a relationship between the resulting porosity and the ramp rate was found. At the lowest investigated ramp rate of 20 °C h-1, the highest porosity of 36% was achieved. For this treatment type, the pore shape was of the ink-bottle type for all investigated ramp rates with narrow 1 nm-sized pores. Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy revealed that the final chemistry of the porous structures was slightly different for both treatments due to trace amounts of carbon left behind by water etching. This suggests that the internal surface of the porous structure has a different termination depending on the chosen treatment. The precise thickness control and conformal nature inherent to MLD combined with the wet and heat treatments enables the coating of complex 3D structures with a porous alumina film with a well-defined thickness and pore structure.

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 °C to 180 °C, with growth rates of 1.2 to 0.5 Å 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. A series of 21 nm vanadicone films were subjected to annealing under oxidizing (air) or inert (He) atmospheres at 500 °C. During annealing in air, the film crystallized to the VO 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 VO reference was observed. However, the helium annealed samples outperformed VO 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 VO-based hybrid electrodes in a wider potential range without sacrificing the stability and performance.

The construction and use of a dual radiator Ring Imaging Cherenkov (RICH) detector is described. This instrument was developed for the HERMES experiment at DESY which emphasises measurements of semi-inclusive deep-inelastic scattering. It provides particle identification for pions, kaons, and protons in the momentum range from 2 to 15 GeV, which is essential to these studies. The instrument uses two radiators, C4F10, a heavy fluorocarbon gas, and a wall of silica aerogel tiles. The use of aerogel in a RICH detector has only recently become possible with the development of clear, large, homogeneous and hydrophobic aerogel. A lightweight mirror was constructed using a newly perfected technique to make resin-coated carbon-fiber surfaces of optical quality. The photon detector consists of 1934 photomultiplier tubes (PMT) for each detector half, held in a soft steel matrix to provide shielding against the residual field of the main spectrometer magnet. (C) 2002 Elsevier Science B.V. All rights reserved

A novel in situ infrared (IR) approach is demonstrated for investigating and identifying ALD surface reactions during both the steady state and the initial growth regime. The unique combination of reflection−absorption IR spectroscopy in grazing incidence mode with a high surface area reflecting substrate allows for ALD process monitoring with an acceptable acquisition time and a high sensitivity in the entire mid-IR spectral region. Using a mesoporous silica film deposited on a reflecting platinum layer as substrate, the thermal and plasma-enhanced ALD processes of alumina with use of trimethylaluminum (TMA) are compared. Due to the high sensitivity of the method, the relative amount of surface hydroxyl groups added or removed during the process could be determined versus the number of ALD half-cycles. These data reveal substrate-inhibited growth on the silica surface for the thermal process with use of TMA and water, as compared to direct growth for the plasma-based ALD process with use of TMA and O 2 plasma. This different behavior could be linked to the formation of Si−CH 3 surface groups after the first precursor pulse, as evidenced by the raw IR spectra. It is found that the oxygen radicals in the plasma can remove these surface groups during the next few ALD cycles, while the H 2 O molecules cannot, thus explaining the initial slower growth for the thermal process. ■ INTRODUCTIONAtomic layer deposition (ALD) is a thin film deposition technique well-known for its precise thickness control and excellent conformality on high-aspect-ratio structures. The process consists of sequential alternating pulses of precursor gases that react with the substrate surface in a self-limiting manner. Because the start of the film growth depends on the chemical nature of the substrate, knowledge of the initial growth kinetics and surface chemistry of ALD is important, especially when ultrathin films of a few nanometers thickness are needed. Each ALD precursor pulse leaves at most a monolayer of precursor molecules on the surface. As a consequence, very sensitive characterization techniques are needed to perform a detailed investigation of the surface reactions after each pulse.Infrared spectroscopy has proven to be a valuable tool for studying surface chemistry during ALD processes. Chabal et al. published several papers demonstrating a transmission IR technique that allows for monitoring of ALD processes on planar substrates. 1−3 George et al. combined transmission geometry with high surface area powders pressed into a grid to improve signal-to-noise ratio and thus reduce measurement times. 4−6 The high surface area improves the quality of the spectra because more surface groups can be detected compared with a planar substrate. However, uniform heating of samples in transmission geometry can be a challenge. 7 Attenuated total reflection (ATR)-FTIR spectroscopy of ALD processes has been reported, but the need for an ATR crystal and the accurate alignment that this setup requires complicate the experiment. 8,9 Sperling et al. ...