Models of insulating interfaces between (100)GaAs and HfO2, Gd2O3, and Al2O3 are constructed and used to host various interfacial defects to see which give rise to gap states. The antibonding state of As–As dimers is found to lie in the upper band gap and is identified as a possible major source of the interface gap states which cause Fermi level pinning in GaAs-oxide interfaces and field effect transistors.

Effective work function tuning in high-κ dielectric metal-oxide-semiconductor stacks by fluorine and lanthanide doping Appl. Phys. Lett. 96, 053506 (2010); 10.1063/1.3303976 Atomic mechanism of flat-band voltage shifts by La 2 O 3 and Al 2 O 3 in gate stacks Appl. Phys. Lett. 95, 012906 (2009);The mechanism of flat-band voltage shifts in La-and Al-based, etc., oxide capping layers in high-K (dielectric constant) metal gate stacks is investigated by ab initio calculations on atomic models. The capping layer dopants are calculated to segregate to the high-K:SiO 2 interface in most cases. An interfacial dipole is observed at both the pure HfO 2 :SiO 2 interface and at oxide doped HfO 2 :SiO 2 interfaces by plotting electrostatic potentials perpendicular to the interfaces. Substitutional La, Sr, Al, Nb, and Ti atoms are calculated to induce potential shifts at the HfO 2 : SiO 2 interface which shift the valence band offset in the experimentally observed directions. The shift does not correlate with the metal's valence, being the opposite for La and Al, which rules out the oxygen vacancy model. The shift does correlate with the metal's group-electronegativity or metal work function. The potential shift due to A-O and O-A bond dipoles cancels out, on average, in the 'bulk' parts of the gate oxide film, and it is only finite where there is a change in the dielectric constant and screening across this buried interface. The net dipole potential shift only comes from those dopant atoms located at the interface itself, not those that diffused away from this interface.

Deepening our understanding of mammalian gut microbiota has been greatly hampered by the lack of a facile, real‐time, and in vivo bacterial imaging method. To address this unmet need in microbial visualization, we herein report the development of a second near‐infrared (NIR‐II)‐based method for in vivo imaging of gut bacteria. Using d‐propargylglycine in gavage and then click reaction with an azide‐containing NIR‐II dye, gut microbiota of a donor mouse was strongly labeled with NIR‐II fluorescence on their peptidoglycan. The bacteria could be readily visualized in recipient mouse gut with high spatial resolution and deep tissue penetration under NIR irradiation. The NIR‐II‐based metabolic labeling strategy reported herein, provides, to the best of our knowledge, the first protocol for facile in vivo visualization of gut microbiota within deep tissues, and offers an instrumental tool for deciphering the complex biology of these gut “dark matters”.

Currently, there are more than 200 fecal microbiota transplantation (FMT) clinical trials worldwide. However, our knowledge of this microbial therapy is still limited. Here we develop a strategy using sequential tagging with D-amino acid-based metabolic probes (STAMP) for assessing the viabilities of transplanted microbiotas. A fluorescent D-amino acid (FDAA) is first administered to donor mice to metabolically label the gut microbiotas in vivo. The labeled microbiotas are transplanted to recipient mice, which receive a second FDAA with a different color. The surviving transplants should incorporate both FDAAs and can be readily distinguished by presenting two colors simultaneously. Isolation of surviving bacteria and 16S rDNA sequencing identify several enriched genera, suggesting the importance of specific bacteria in FMT. In addition, using STAMP, we evaluate the effects on transplant survival of pre-treating recipients using different antibiotics. We propose STAMP as a versatile tool for deciphering the complex biology of FMT, and potentially improving its treatment efficacy.

The paper describes the reasons for the greater difficulty in the passivation of interface defects of III-V semiconductors like GaAs. These include the more complex reconstructions of the starting surface which already possess defect configurations, the possibility of injecting As antisites into the substrate which give rise to gap states, and the need to avoid As-As bonds and As dangling bonds which give rise to gap states. The nature of likely defect configurations in terms of their electronic structure is described. The benefits of diffusion barriers and surface nitridation are discussed.

The origin of the flat-band voltage shifts for La- and Al-based oxide capping layers in high k metal gate stacks is studied by ab initio calculations on atomic models. Substitutional La, Al, Sr, and Nb at the HfO2–SiO2 interface create dipoles, which shift the flat band voltage in the experimentally observed direction, negative for La and Sr and positive for Al and Nb. The shift does not correlate with the metal’s valence, being opposite for La and Al, which rules out a vacancy model. The shift does correlate with the metal electronegativity/work function. It does not correlate with oxygen ion density, as this is not varied.

Current techniques for studying gut microbiota are unable to answer some important microbiology questions, like how different bacteria grow and divide in the gut. We propose a method that integrates the use of sequential d-amino acid–based in vivo metabolic labeling with fluorescence in situ hybridization (FISH), for characterizing the growth and division patterns of gut bacteria. After sequentially administering two d-amino acid–based probes containing different fluorophores to mice by gavage, the resulting dual-labeled peptidoglycans provide temporal information on cell wall synthesis of gut bacteria. Following taxonomic identification with FISH probes, the growth and division patterns of the corresponding bacterial taxa, including species that cannot be cultured separately in vitro, are revealed. Our method offers a facile yet powerful tool for investigating the in vivo growth dynamics of the bacterial gut microbiota, which will advance our understanding of bacterial cytology and facilitate elucidation of the basic microbiology of this gut “dark matter.”

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