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Delayed atomic layer deposition (ALD) of ZnO, i.e., area selective (AS)-ALD, was successfully achieved on silicon wafers (SiSiO2) terminated with tris(dimethylamino)methylsilane (TDMAMS). This resist molecule was deposited in a home-built, near-atmospheric pressure, flow-through, gas-phase reactor. TDMAMS had previously been shown to react with SiSiO2 in a single cycle/reaction and to drastically reduce the number of silanols that remain at the surface. ZnO was deposited in a commercial ALD system using dimethylzinc (DMZ) as the zinc precursor and H2O as the coreactant. Deposition of TDMAMS was confirmed by spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), and wetting. ALD of ZnO, including its selectivity on TDMAMS-terminated SiSiO2 (SiSiO2TDMAMS), was confirmed by in situ multi-wavelength ellipsometry, ex situ SE, XPS, and/or high-sensitivity/low-energy ion scattering (HS-LEIS). The thermal stability of the TDMAMS resist layer, which is an important parameter for AS-ALD, was investigated by heating SiSiO2TDMAMS in air and nitrogen at 330 °C. ALD of ZnO takes place more readily on SiSiO2TDMAMS heated in the air than in N2, suggesting greater damage to the surface heated in the air. To better understand the in situ ALD of ZnO on SiSiO2TDMAMS and modified (thermally stressed) forms of it, the ellipsometry results were plotted as the normalized growth per cycle. Even one short pulse of TDMAMS effectively passivates SiSiO2. TDMAMS can be a useful, small-molecule inhibitor of ALD of ZnO on SiSiO2 surfaces.

Surface silanols (SiOH) are important moieties on glass surfaces. Here we present a tag-and-count approach for determining surface silanol densities, which consists of tagging surface silanols with Zn via atomic layer deposition (ALD) followed by detection of the zinc by high sensitivity-low energy ion scattering (HS-LEIS). Shards of fused silica were hydroxylated with aqueous hydrofluoric acid (HF) and then heated to 200, 500, 700, or 900 °C. These heat treatments increasingly condense and remove surface silanols. The samples then underwent one ALD cycle with dimethylzinc (DMZ) or diethylzinc (DEZ) followed by water. As expected, fused silica surfaces heated to higher temperatures showed lower Zn coverages. When fused silica surfaces treated at 200 °C were exposed to DMZ for two different dose times, the same sub-monolayer quantity of Zn was obtained by X-ray photoelectron spectroscopy (XPS). Surface cleaning/preparation immediately before HS-LEIS, including atomic oxygen treatment and annealing, played a critical role in these efforts. Surfaces treated with DMZ generally showed slightly higher Zn signals by LEIS. Using this methodology, a value of 4.59 OH/nm2 was found for fully hydroxylated fused silica. Both this result and those obtained at 500, 700, and 900 °C are in very good agreement with literature values.

A combination of surface sensitive techniques was used to determine the surface structure and chemistry of La2-xSrxNiO 4+δ. These measurements unequivocally showed that Ni is not present in the outermost atomic layer, suggesting that the accepted model with the B-site cations exposed to the environment is incorrect.

Low-energy ion scattering (LEIS) can be used to selectively analyse the atomic composition of the outer atomic layer of a catalyst, i.e., precisely the atoms that largely determine its activity and selectivity. It is shown how a new development in LEIS significantly improves its mass resolution. Using this advanced separation and quantification of signals from platinum and gold, the atomic composition of the outer surface of a realistic supported platinum-gold bimetallic system can be determined for the first time.

High Sensitivity-Low Energy Ion Scattering (HS-LEIS) is a sensitive analysis technique for the outermost atomic layer of a sample. On a heterogeneous catalyst, this outermost atomic layer is the precise location where the catalytic processes take place. Based on the principles of classical mechanics, HS-LEIS determines the mass of surface atoms by measuring the energy from ions that are scattered from the surface. Examples with pure oxides, mixed oxides and supported metal oxide catalyst samples are presented to demonstrate the sensitivity, the ease of quantification, the availability of information about layers immediately beneath the surface (relevant for the dispersion of the active catalytic component on the surface of the catalyst) as well as the potential for High Throughput Experimentation (HTE) due to the short analysis times.

Aluminum nitride-type species were prepared on porous alumina and silica by repeated separate, saturated reactions of gaseous trimethylaluminum (TMA) and ammonia with solid substrates. Reaction cycles of TMA at 423 K and ammonia at 823 K were performed up to six times. Growth per cycle was on average 2.4 AlN units/nm2, but it increased slightly with the number of reaction cycles. The amount of hydrogen present in NHx groups increased with the increasing number of reaction cycles. AlN4 units were observed by 27Al NMR on alumina, but the AlN remained amorphous to X-ray diffraction. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy revealed that the AlN-type species were spread out evenly on the surface of the particles. TMA reacted with equal probability with the still-exposed silica and the AlN-type species present on the surface, as shown by low-energy ion scattering. 29Si and 27Al NMR suggested that transition from the oxide substrates to aluminum nitride occurred through silicon oxynitride for the silica substrate and through aluminum oxynitride for both substrates.

The determination of the mass transport kinetics of oxide materials for use in electrochemical systems such as fuel cells, sensors and oxygen separators is a significant challenge. Several techniques have been proposed to derive these data experimentally with only the oxygen isotope exchange depth profile technique coupled with secondary ion mass spectrometry (SIMS) providing a direct measure of these kinetic parameters. Whilst this allows kinetic information to be obtained, there is a lack of knowledge of the surface chemistry of these complex processes. The advent of low-energy ion scattering (LEIS) now offers the opportunity of correlating exchange kinetics with chemical processes at materials atomic surfaces, giving unprecedented levels of information on electrochemical systems with isotopic discrimination. Here, the challenges of these techniques, including sample preparation, are discussed and the advantages of the combined approach of SIMS and LEIS illustrated with reference to key literature data.

Quantitative analysis in low-energy ion scattering (LEIS) requires an understanding of the charge-exchange processes to estimate the elemental sensitivity factors. In this work, the neutralization of He+ scattered by 18O-exchanged silica at energies between 0.6 and 7 keV was studied. The process is dominated by Auger neutralization for Ei 2 keV. The ion fractions P+ were determined for Si and O using the characteristic velocity method to quantify the surface density. The 18O/16O sensitivity ratio indicates an 18% higher sensitivity for the heavier O isotope.