Growth kinetics of Si on fullsheet, patterned and silicon-on-insulator substrates

International audienceUsing a reduced pressure-chemical vapor deposition cluster tool, we have studied the epitaxial growth of Si using either a silane or a dichlorosilane+hydrochloric acid chemistry on fullsheet, patterned and silicon-on-insulator (SOI) substrates. We have first of all developed a (''HF-last'' advanced wet cleaning+low thermal budget (775°C, 2 min) in situ H$_2$ bake) combination that yields atomically smooth, contamination free Si starting surfaces for both fullsheet and patterned wafers. We have then modeled the low temperature Si growth rate (silane or dichlorosilane+hydrochloric acid chemistry) on fullsheet wafers. A similar growth rate activation energy is found for both chemistries, i.e. $E_{GR}$~ 50 kcal mol$^{-1}$. The growth rate dependency on the Si precursor flow is vastly different, however. Fitting this dependency with a simple power law, a value of 0.36 is indeed associated to dichlorosilane, versus 0.92 for silane. The HCl etching rate is characterized by an activation energy $E_{ER}$~34 kcal mol$^{-1}$ , with a 0.52 power law dependency on the HCl flow. On patterned wafers, we have demonstrated that a deposited Si thickness limit (20 nm) exists at 775°C for high $F$(HCl)/$F$(SiH$_2$Cl$_2$) mass flow ratios. This limit disappears when (i) $F$(HCl)/$F$(SiH$_2$Cl$_2$) is reduced (ii) the growth temperature is increased to 800°C. Finally, we have highlighted the specifics of the growth on SOI wafers. A significant growth rate reduction (compared to bulk Si) has been evidenced on ultra-thin Si over-layer SOI wafers. It gets less and less pronounced as the buried oxide layer gets thinner and/or the Si over-layer thickness increases

Evolution of green lacewings (Neuroptera: Chrysopidae): an anchored phylogenomics approach

Table S1. Taxa used in this study, including SRA accession numbers.Table S2. Divergence time estimates (mean ages and ranges) and branch support values for nodes in Figs 2 and S1. PP, posterior probability.Figure S1. Chronogram node numbers and fossils.Figure S2. Maximum likelihood phylogeny of Chrysopidae using AHE data. Bootstrap support values are indicated on nodes and grouped by colour according to value.Figure S3. Nucleotide Astral tree.Figure S4. BAMM plot showing the two most common shift configurations in the credible set. The ‘f’ number corresponds to the proportion of the posterior samples in which this configuration is present.Figure S5. Macroevolutionary cohort matrix for diversifica-tion. Each cell in the matrix is coded by a colour denoting the pairwise probability that two species share a common macroevolutionary rate regime. The maximum clade credi-bility tree is shown for reference in the left and upper margins of each cohort matrix.Figure S6. BAMM rate shift tree showing the overall best fit configuration. Red circles signify placement of shifts.File S1. Chrysopidae Anchored hybrid enrichment alignment. (https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1111%2Fsyen.12347&file=syen12347-sup-0001-FileS1.txt)File S2. Chrysopidae anchored hybrid enrichment, partition datasets. (https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1111%2Fsyen.12347&file=syen12347-sup-0002-FileS2.txt)A phylogeny of green lacewings (Neuroptera: Chrysopidae) using anchored hybrid enrichment data is presented. Using this phylogenomic approach, we analysed 137 kb of sequence data (with < 10% missing) for 82 species in 50 genera of Chrysopidae under Bayesian and maximum likelihood criteria. We recovered a strongly supported tree topologically congruent with recently published phylogenies, especially relationships amongst higher‐level groups. The subfamily Nothochrysinae was recovered as paraphyletic, with one clade sister to the rest of Chrysopidae, and the second clade containing the nominal genus (Nothochrysa Navás) as sister to the subfamily Apochrysinae. Chrysopinae was recovered as a monophyletic with the monobasic Nothancylini tribe n. sister to the rest of the subfamily. Leucochrysini was recovered sister to Belonopterygini, and Chrysopini was rendered paraphyletic with respect to Ankylopterygini. Divergence times and diversification estimates indicate a major shift in rate in ancestral Chrysopini at the end of the Cretaceous, and the extensive radiation of Chrysopinae, the numerically dominant clade of green lacewings, began in the Mid‐Paleogene (c. 45 Ma).Brazilian National Council for Scientific and Technological Development (209447/2013–3, to JPG), the US National Science Foundation (DEB-1144119, to SLW; DEB-1144162, to MSE; and DEB-0933588, to JDO) and the Beijing Natural Science Foundation (5162016) (to XL).https://onlinelibrary.wiley.com/journal/136531132020-07-01hj2019Zoology and Entomolog

Rethinking models of pattern formation in somitogenesis

A new model for somite formation calls prevailing models into question