Vanadium oxide monolayer catalysts : The vapor-phase oxidation of methanol

The oxidation of methanol over vanadium oxide, unsupported and applied as a monolayer on γ-Al2O3, CeO2, TiO2, and ZrO2, was studied between 100 and 400 °C in a continuous-flow reactor. At temperatures from 150 to about 250 °C two main reactions take place, (a) dehydration of methanol to dimethyl ether and (b) partial oxidation to formaldehyde. A very slight direct oxidation to CO2 proceeds simultaneously. At higher temperatures two further reactions take place, i.e., (c) consecutive oxidation of the ether and/or formaldehyde to CO and (d) consecutive oxidation of CO to CO2. Selectivity to formaldehyde increased with decreasing reducibility of the catalyst, which in turn was a function of the catalyst-support interactions. Since the reducibility of V(V) has been shown to be related to the charge/radius ratio of the cation of the carrier, the selectivity to formaldehyde is also determined by this ratio

High‐throughput area‐selective spatial atomic layer deposition of SiO 2 with interleaved small molecule inhibitors and integrated back‐etch correction for low defectivity

A first‐of‐its‐kind area‐selective deposition process for SiO2 is developed consisting of film deposition with interleaved exposures to small molecule inhibitors (SMIs) and back‐etch correction steps, within the same spatial atomic layer deposition (ALD) tool. The synergy of these aspects results in selective SiO2 deposition up to ~23 nm with high selectivity and throughput, with SiO2 growth area and ZnO nongrowth area. The selectivity is corroborated by both X‐ray photoelectron spectroscopy (XPS) and low‐energy ion scattering spectroscopy (LEIS). The selectivity conferred by two different SMIs, ethylbutyric acid, and pivalic acid has been compared experimentally and theoretically. Density Functional Theory (DFT) calculations reveal that selective surface functionalization using both SMIs is predominantly controlled thermodynamically, while the better selectivity achieved when using trimethylacetic acid can be explained by its higher packing density compared to ethylbutyric acid. By employing the trimethylacetic acid as SMI on other starting surfaces (Ta2O5, ZrO2, etc.) and probing the selectivity, a broader use of carboxylic acid inhibitors for different substrates is demonstrated. It is believed that the current results highlight the subtleties in SMI properties such as size, geometry, and packing, as well as interleaved back‐etch steps, which are key in developing ever more effective strategies for highly selective deposition processes

Atomic layer deposition applications 12

The objective of the current study was to explore the role of ABCB1 and CYP3A5 genetic polymorphisms in predicting the bioavailability of tacrolimus and the risk for post-transplant diabetes. Artificial neural network (ANN) and logistic regression (LR) models were used to predict the bioavailability of tacrolimus and risk for post-transplant diabetes, respectively. The five-fold cross-validation of ANN model showed good correlation with the experimental data of bioavailability (r2 = 0.93-0.96). Younger age, male gender, optimal body mass index were shown to exhibit lower bioavailability of tacrolimus. ABCB1 1236 C>T and 2677G>T/A showed inverse association while CYP3A5*3 showed a positive association with the bioavailability of tacrolimus. Gender bias was observed in the association with ABCB1 3435 C>T polymorphism. CYP3A5*3 was shown to interact synergistically in increasing the bioavailability in combination with ABCB1 1236 TT or 2677GG genotypes. LR model showed an independent association of ABCB1 2677 G>T/A with post transplant diabetes (OR: 4.83, 95% CI: 1.22-19.03). Multifactor dimensionality reduction analysis (MDR) revealed that synergistic interactions between CYP3A5*3 and ABCB1 2677 G>T/A as the determinants of risk for post-transplant diabetes. To conclude, the ANN and MDR models explore both individual and synergistic effects of variables in modulating the bioavailability of tacrolimus and risk for post-transplant diabetes

Area-selective atomic layer deposition of ZnO by area activation using electron beam-induced deposition

Area-selective atomic layer deposition (ALD) of ZnO was achieved on SiO2 seed layer patterns on H-terminated silicon substrates, using diethylzinc (DEZ) as the zinc precursor and H2O as the coreactant. The selectivity of the ALD process was studied using in situ spectroscopic ellipsometry and scanning electron microscopy, revealing improved selectivity for increasing deposition temperatures from 100 to 300 °C. The selectivity was also investigated using transmission electron microscopy and energy-dispersive X-ray spectroscopy. Density functional theory (DFT) calculations were performed to corroborate the experimental results obtained and to provide an atomic-level understanding of the underlying surface chemistry. A kinetically hindered proton transfer reaction from the H-terminated Si was conceived to underpin the selectivity exhibited by the ALD process. By combining the experimental and DFT results, we suggest that the trend in selectivity with temperature may be due to a strong DEZ or H2O physisorption on the H-terminated Si that hampers high selectivity at low deposition temperature. This work highlights the deposition temperature as an extra process parameter to improve the selectivity