Proton Affinities of the Silatranes and Their Analogues

Ab initio calculations with full geometry optimization have been used to investigate the O and N atom proton affinities and the molecular structures of silatranes (RSi(OCH2CH2)3N), as well as the related compounds RSi(OCH3)3, RSi(OCH2)3CH, and RSi(OCH2CH2)3CH, where R = F, Cl, CH3, SiH3, utilizing the 6-31G(d) basis set. It is found that larger electron donor substituents R induce large proton affinities. The silatranes have stronger proton affinities than the other compounds because of the transannular Si−N interaction. For silatranes, only a small difference between the O and N atom proton affinities is found. The silatrane Si−R bond distances are apparently determined by the degree of the anomeric effect in the R−Si−O fragment and transannular Si−N interactions

Proton Affinities of the Silatranes and Their Analogues

Ab initio calculations with full geometry optimization have been used to investigate the O and N atom proton affinities and the molecular structures of silatranes (RSi(OCH2CH2)3N), as well as the related compounds RSi(OCH3)3, RSi(OCH2)3CH, and RSi(OCH2CH2)3CH, where R = F, Cl, CH3, SiH3, utilizing the 6-31G(d) basis set. It is found that larger electron donor substituents R induce large proton affinities. The silatranes have stronger proton affinities than the other compounds because of the transannular Si−N interaction. For silatranes, only a small difference between the O and N atom proton affinities is found. The silatrane Si−R bond distances are apparently determined by the degree of the anomeric effect in the R−Si−O fragment and transannular Si−N interactions.Reprinted (adapted) with permission from Organometallics 20 (2001): 927, doi:10.1021/om000875m. Copyright 2001 American Chemical Society.</p

Hydrogen mediated transport of Sn to Ru film surface

The authors report on the interaction of atomic hydrogen with Sn and thin Ru film at room temperature. The study is done using a combination of photoelectron and low energy ion scattering spectroscopies as well as scanning electron microscopy. The adsorption of hydrogen on a Sn surface leads to the formation of stannane (SnH4), which dissociatively adsorbs on the surface of polycrystalline Ru film. In the range of effective Sn coverages studied (up to 1 ML), the resulting overlayer consists of randomly distributed three-dimensional islands with average size below 40 nm occupying up to several percent of the surface area. Nucleation of Sn is observed presumably at defect sites (e.g., grain boundaries). Ion scattering data are found consistent with Volmer–Weber growth mode: no initial transition wetting layer formation is detected. Oxidation of Sn islands on a Ru surface at room temperature results in the formation of SnO. Neither metallic nor oxidation states of Sn higher than Sn2+ are observed by photoelectron spectroscopy.QN/Quantum NanoscienceApplied Science

InAs-Al Hybrid Devices Passing the Topological Gap Protocol

We present measurements and simulations of semiconductor-superconductor heterostructure devices that are consistent with the observation of topological superconductivity and Majorana zero modes. The devices are fabricated from high-mobility two-dimensional electron gases in which quasi-one-dimensional wires are defined by electrostatic gates. These devices enable measurements of local and non-local transport properties and have been optimized via extensive simulations for robustness against non-uniformity and disorder. Our main result is that several devices, fabricated according to the design's engineering specifications, have passed the topological gap protocol defined in Pikulin {\it et al.}\ [arXiv:2103.12217]. This protocol is a stringent test composed of a sequence of three-terminal local and non-local transport measurements performed while varying the magnetic field, semiconductor electron density, and junction transparencies. Passing the protocol indicates a high probability of detection of a topological phase hosting Majorana zero modes. Our experimental results are consistent with a quantum phase transition into a topological superconducting phase that extends over several hundred millitesla in magnetic field and several millivolts in gate voltage, corresponding to approximately one hundred micro-electron-volts in Zeeman energy and chemical potential in the semiconducting wire. These regions feature a closing and re-opening of the bulk gap, with simultaneous zero-bias conductance peaks at {\it both} ends of the devices that withstand changes in the junction transparencies. The measured maximum topological gaps in our devices are 20-$30\,\mu$eV. This demonstration is a prerequisite for experiments involving fusion and braiding of Majorana zero modes.Comment: Fixed typos. Fig. 3 is now readable by Adobe Reade