Extending growth inhibition during area-selective atomic layer deposition of Al2O3 on aminosilane-functionalized SiO2.

During area-selective atomic layer deposition (ALD) based on growth inhibitors, nucleation eventually occurs as the metal precursor reacts with the surface through secondary pathways. We show that ALD of Al2O3 on functionalized SiO2 can be significantly delayed by using a lower reactivity, heteroleptic precursor at well below the saturation dose.

Relation between Reactive Surface Sites and Precursor Choice for Area-Selective Atomic Layer Deposition Using Small Molecule Inhibitors.

Implementation of vapor/phase dosing of small molecule inhibitors (SMIs) in advanced atomic layer deposition (ALD) cycles is currently being considered for bottom-up fabrication by area-selective ALD. When SMIs are used, it can be challenging to completely block precursor adsorption due to the inhibitor size and the relatively short vapor/phase exposures. Two strategies for precursor blocking are explored: (i) physically covering precursor adsorption sites, i.e., steric shielding, and (ii) eliminating precursor adsorption sites from the surface, i.e., chemical passivation. In this work, it is determined whether steric shielding is enough for effective precursor blocking during area-selective ALD or whether chemical passivation is required as well. At the same time, we address why some ALD precursors are more difficult to block than others. To this end, the blocking of the Al precursor molecules trimethylaluminum (TMA), dimethylaluminum isopropoxide (DMAI), and tris(dimethylamino)aluminum (TDMAA) was studied by using acetylacetone (Hacac) as inhibitor. It was found that DMAI and TDMAA are more easily blocked than TMA because they adsorb on the same surface sites as Hacac, while TMA is also reactive with other surface sites. This work shows that chemical passivation plays a crucial role for precursor blocking in concert with steric shielding. Moreover, the reactivity of the precursor with the surface groups on the non-growth area dictates the effectiveness of blocking precursor adsorption.

Biostimulation of Anaerobic Digestion Using Iron Oxide Nanoparticles (IONPs) for Increasing Biogas Production from Cattle Manure.

The effect of synthesised IONPs employing a nontoxic leaf extract of Azadirachta indica as a reducing, capping, and stabilizing agent for increasing biogas and methane output from cattle manure during anaerobic digestion (AD) was investigated in this study. Furthermore, the UV-visible spectra examination of the synthesized nanoparticles revealed a high peak at 432 nm. Using a transmission electron microscope, the average particle size of IONPs observed was 30-80 nm, with irregular, ultra-small, semi-spherical shapes that were slightly aggregated and well-distributed. IONPs had a polydisparity index (PDI) of 219 nm and a zeta potential of -27.0 mV. A set of six bio-digesters were fabricated and tested to see how varying concentrations of IONPs (9, 12, 15, 18, and 21 mg/L) influenced biogas, methane output, and effluent chemical composition from AD at mesophilic temperatures (35 ± 2 °C). With 18 mg/L IONPs, the maximum specific biogas and methane production were 136.74 L/g of volatile solids (VS) and 64.5%, respectively, compared to the control (p < 0.05), which provided only 107.09 L/g and 51.4%, respectively. Biogas and methane production increased by 27.6% and 25.4%, respectively using 18 mg/L IONPs as compared to control. In all treatments, the pH of the effluent was increased, while total volatile fatty acids, total solids, volatile solids, organic carbon content, and dehydrogenase activity decreased. Total solid degradation was highest (43.1%) in cattle manure + 18 mg/L IONPs (T5). According to the results, the IONPs enhanced the yield of biogas and methane when compared with controls.

Functionalization of the SiO2 Surface with Aminosilanes to Enable Area-Selective Atomic Layer Deposition of Al2O3.

Small-molecule inhibitors are promising for achieving area-selective atomic layer deposition (ALD) due to their excellent compatibility with industrial processes. In this work, we report on growth inhibition during ALD of Al2O3 on a SiO2 surface functionalized with small-molecule aminosilane inhibitors. The SiO2 surface was prefunctionalized with bis(dimethylamino)dimethylsilane (BDMADMS) and (N,N-dimethylamino)trimethylsilane (DMATMS) through solution and the vapor phase. ALD of Al2O3 using dimethylaluminum isopropoxide (DMAI) and H2O was performed on these functionalized SiO2 surfaces. Our in situ four-wavelength ellipsometry measurements show superior growth inhibition when using BDMADMS and DMATMS in sequence over just using BDMADMS or DMATMS. Vapor phase functionalization provided a growth delay of ∼30 ALD cycles, which was similar to solution-based functionalization. Using in situ attenuated total reflection Fourier transform infrared spectroscopy, we show that the interaction of DMAI with SiO2 surfaces leads to pronounced changes in absorbance for the Si-O-Si phonon mode without any detectable DMAI absorbed on the SiO2 surface. Detailed analysis of the infrared spectra revealed that the decrease in absorbance was likely caused by the coordination of Al in DMAI to O atoms in surface Si-O-Si bonds without the breaking the Si-O-Si bonds. Finally, we postulate that a minimal amount of DMAI remains adsorbed on surface Si-O-Si bonds even after purging, which can initiate ALD of Al2O3 on functionalized SiO2: this highlights the need for higher surface coverage for enhanced steric blocking.

Acute lymphoblastic leukemia and genetic variations in BHMT gene: Case-control study and computational characterization.

BACKGROUND: Remethylation of homocysteine is catalyzed by B12 dependent methionine synthase (MTR) in all types of cells and by B12 non-dependent betaine homocysteine methyltransferase (BHMT) in liver and kidney cells. Of many etiologies of cancer, an unexplored area is the variations of genes implicated in methylation reaction. OBJECTIVE: The study evaluated the association of BHMT (rs3733890) with acute lymphoblastic leukemia (ALL), followed by in-silico characterization of variations in BHMT gene. METHODS: BHMT [rs3733890; c.742G > A, which substitutes an arginine by a glutamine at codon 239 (R239Q)] was screened by Tetra-primer Amplification Refractory Mutation System PCR (T-ARMS-PCR) and confirmed using DNA sequencing. In-silico analysis was conducted using bioinformatics tools. RESULTS: BHMT (rs3733890) showed an insignificant association with both childhood and adult ALL. Bioinformatics analysis showed that 18 nsSNPs are deleterious, 3 SNPs in 3'-UTR (rs59109725, rs116634518 and rs138578732) alter the miRNA-binding site, and 11 CNVs are present in the BHMT gene. As consequence of BHMT (rs3733890) polymorphism the free energy changes from -101210.1 kJ/mol to -200021.8 kJ/mol. CONCLUSIONS: BHMT (rs3733890) polymorphism showed no association with ALL. Hence this investigation needs further evaluation in larger sample size and effect of other SNPs, CNVs and miRNA's is required to elucidate the role of BHMT gene in ALL development.