Mechanism of inward oxygen diffusion on H-, OH-, and nonterminated silicon surfaces

Abstract

Generation of an electrochemical proton gradient is the first step of cell bioenergetics. In prokaryotes, the gradient is created by outward membrane protein proton pumps. Inward plasma membrane native proton pumps are yet unknown. We describe comprehensive functional studies of the representatives of the yet noncharac-terized xenorhodopsins from Nanohaloarchaea family of microbial rhodopsins. They are inward proton pumps as we demonstrate in model membrane systems, Escherichia coli cells, human embryonic kidney cells, neuro-blastoma cells, and rat hippocampal neuronal cells. We also solved the structure of a xenorhodopsin from the nanohalosarchaeon Nanosalina (NsXeR) and suggest a mechanism of inward proton pumping. We demonstrate that the NsXeR is a powerful pump, which is able to elicit action potentials in rat hippocampal neuronal cells up to their maximal intrinsic firing frequency. Hence, inwardly directed proton pumps are suitable for light-induced remote control of neurons, and they are an alternative to the well-known cation-selective channelrhodopsins.

Oxidation of Hydrogenated Si(111) by a Radical Propagation Mechanism

“…On the other hand, the energy barrier for the diffusion of an O atom in the first bilayer toward the Si−Si bond between the first and second bilayer is 85.5 kcal/mol. 24 This value is nearly twice as large as the barrier for the diffusion within the first bilayer (Figure 3). This is the reason why the oxidation of silicon occurs layer by layer.…”

“…In conclusion, the high energy barriers for the diffusion of oxygen atoms between adjacent back bonds cannot explain the formation of patches at room temperature. On the other hand, the energy barrier for the diffusion of an O atom in the first bilayer toward the Si–Si bond between the first and second bilayer is 85.5 kcal/mol . This value is nearly twice as large as the barrier for the diffusion within the first bilayer (Figure ).…”

First principles analysis of the initial oxidation of Si(001) and Si(111) surfaces terminated with H and CH3

“…Furthermore, since initial stage oxidation is a complicated dynamic process that almost certainly depends on O coverage, the effective barrier measured experimentally cannot be directly compared with the calculated barrier for a single O 2 adsorbed on the non-oxidized surface. The mobility of adsorbed O atoms was theoretically studied by Hoshino and Eyre 44,45 who estimated the activation barriers for inward diffusion of an O atom on H-Si(111) and OH-(111) surfaces to be approximately 4 eV, much larger than that on the corresponding bare surface.…”

Influence of an In-Situ Formed Interfacial SiNx Layer on the Electrical Performance and Thermal Stability of High-k HfO2 Films

“…6) was done. 6 A notable difference in the XPS results is the intensity of the Si 4+ and silicate peaks. After PDA, the TDMAH HfO 2 film forms more Si 4+ than silicate states.…”