Molecular layer deposition (MLD) is an increasingly used deposition technique for producing thin coatings consisting of purely organic or hybrid inorganic-organic materials. When organic materials are prepared, low deposition temperatures are often required to avoid decomposition, thus causing problems with low vapor pressure precursors. Monofunctional compounds have higher vapor pressures than traditional bi- or trifunctional MLD precursors, but do not offer the required functional groups for continuing the MLD growth in subsequent deposition cycles. In this study, we have used high vapor pressure monofunctional aromatic precursors in combination with ozone-triggered ring-opening reactions to achieve sustained sequential growth. MLD depositions were carried out by using three different aromatic precursors in an ABC sequence, namely with TMA + phenol + O, TMA + 3-(trifluoromethyl)phenol + O, and TMA + 2-fluoro-4-(trifluoromethyl)benzaldehyde + O. Furthermore, the effect of hydrogen peroxide as a fourth step was evaluated for all studied processes resulting in a four-precursor ABCD sequence. According to the characterization results by ellipsometry, infrared spectroscopy, and X-ray reflectivity, self-limiting MLD processes could be obtained between 75 and 150 °C with each of the three aromatic precursors. In all cases, the GPC (growth per cycle) decreased with increasing temperature. In situ infrared spectroscopy indicated that ring-opening reactions occurred in each ABC sequence. Compositional analysis using time-of-flight elastic recoil detection indicated that fluorine could be incorporated into the film when 3-(trifluoromethyl)phenol and 2-fluoro-4-(trifluoromethyl)benzaldehyde were used as precursors.
In this paper, we have optimized a low-temperature atomic layer deposition (ALD) of SiO
2
using AP-LTO® 330 and ozone (O
3
) as precursors, and demonstrated its suitability to surface-modify temperature-sensitive bio-based films of cellulose nanofibrils (CNFs). The lowest temperature for the thermal ALD process was 80°C when the silicon precursor residence time was increased by the stop-flow mode. The SiO
2
film deposition rate was dependent on the temperature varying within 1.5–2.2 Å cycle
−1
in the temperature range of 80–350°C, respectively. The low-temperature SiO
2
process that resulted was combined with the conventional trimethyl aluminium + H
2
O process in order to prepare thin multilayer nanolaminates on self-standing CNF films. One to six stacks of SiO
2
/Al
2
O
3
were deposited on the CNF films, with individual layer thicknesses of 3.7 nm and 2.6 nm, respectively, combined with a 5 nm protective SiO
2
layer as the top layer. The performance of the multilayer hybrid nanolaminate structures was evaluated with respect to the oxygen and water vapour transmission rates. Six stacks of SiO
2
/Al
2
O with a total thickness of approximately 35 nm efficiently prevented oxygen and water molecules from interacting with the CNF film. The oxygen transmission rates analysed at 80% RH decreased from the value for plain CNF film of 130 ml m
−2
d
−1
to 0.15 ml m
−2
d
−1
, whereas the water transmission rates lowered from 630 ± 50 g m
−2
d
−1
down to 90 ± 40 g m
−2
d
−1
.
This article is part of a discussion meeting issue ‘New horizons for cellulose nanotechnology’.
Here, the authors report on the preparation of core-shell carbon-ceramic fibrous as well as ceramic tubular catalyst supports utilizing electrospinning and atomic layer deposition (ALD). In this paper, ALD of Ti-Nb-O thin films using TiCl 4 , Nb(OEt) 5 , and H 2 O as precursors is demonstrated. According to the time-of-flight-elastic recoil detection analysis and Rutherford backscattering spectrometry, carbon and hydrogen impurities were relatively low, but depend on the pulsing ratio of the precursors. Optimized ALD process was used for coating of sacrificial electrospun polyvinyl alcohol (PVA) template fibers to yield tubular Ti-Nb-O structures after thermal or solution based PVA removal. Another approach utilized 200-400 nm thick carbon fibers prepared by electrospinning from polyacrylonitrile and subsequent thermal treatment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.