LEEM提出法国生物医药议案

法国制药工业协会LEEM现已提出5项主要议案，旨在建立一个法国“医学生物医药分部”。

解说低能量/光电子显微镜(LEEM/PEEM)

文章介绍近年来倍受关注的低能量/光电子显微镜(LEEM/PEEM)的基本原理和应用.LEEM/PEEM拥有成像、光电子能谱和衍射功能,可对样品进行综合全面的分析.通过一系列的应用实例,特别是和同步辐射软X射线结合的成果,展示该实验手段在表面科学和纳米技术方面的应用.

马拉色菌培养基的改良及应用

目的改良传统的Leeming&Notman培养基,提高马拉色菌的培养效率,并实际应用。方法设立含1%橄榄油、2%橄榄油和4%橄榄油的培养基组。在培养第3、5、7日测量菌落直径,提取基因组DNA并检测浓度,扩增ITS1-2区比较PCR产物质量。结果马拉色菌在含4%橄榄油的培养基上生长最为迅速,产出的基因组DNA量最大,扩增得到的ITS1-2区产物质量最佳。结论改良的含4%橄榄油的Leeming&Notman培养基有利于提高马拉色菌科研工作的效率。

Ytterbium Intercalation of Epitaxial Graphene Grown on Si-Face SiC

The rare-earth metal, ytterbium (Yb), was deposited on graphene grown on Si-face SiC, kept at room temperature. Yb was not found to intercalate, destroy or dope the graphene layer before subsequent heating, unlike alkali metals such as Li and Na. Our photoemission results reveal that heating to 300oC promotes Yb intercalation into the graphene-substrate interface. Real-time low energy electron microscopy (LEEM) measurements indicated intercalation to start at a sample temperature of around 220oC. In the intercalation process, Yb penetrates through the graphene and buffer layer and forms bonds to the silicon in the topmost SiC substrate bilayer, as indicated by the shifted components observed in the C 1s, Si 2p, and Yb 4f spectra. The Yb intercalation decouples the buffer layer from the substrate and transforms it into another graphene layer as manifested by the absence of buffer layer spots in the μ-LEED pattern and the appearance of an additional π band in the ARPES spectra, respectively. Moreover, the observed shift of the Dirac point down from the Fermi level by 1.9 eV indicates electron doping of the graphene layer upon Yb intercalation. The Yb intercalated graphene sample was found to be thermodynamically stable up to temperatures around 700oC.

Growth and low-energy electron microscopy characteri- zation of monolayer hexagonal boron nitride on epitaxial cobalt

Low-energy electron microscopy （LEEM） has been used to study the structure, initial growth orientation, growth progression, and the number of layers of atomically thin hexagonal boron nitride （h-BN） films. The h-BN films are grown on heteroepitaxial Co using chemical vapor deposition （CVD） at low pressure. Our findings from LEEM studies include the growth of monolayer film having two, oppositely oriented, triangular BN domains commensurate with the Co lattice. The growth of h-BN appears to be self-limiting at a monolayer, with thicker domains only appearing in patches, presumably initiated between domain boundaries. Reflectivity measurements of the thicker h-BN films show oscillations resulting from the resonant electron transmission through quantized electronic states of the h-BN films, with the number of minima scaling up with the number of h-BN layers. First principles density functional theory （DFT） calculations show that the positions of oscillations are related to the electronic band structure of h-BN.

Oxygen intercalation under hexagonal boron nitride(h-BN)on Pt(111)

The interface between a two-dimensional(2D)atomic crystal and a metal surface can be regarded as a nanoreactor, in which molecule adsorption and catalytic reactions may occur. In this work, we demonstrate that oxygen intercalation and desorption occur at the interface between hexagonal boron nitride(h-BN) overlayer and Pt(111) surface by using near-ambient pressure X-ray photoelectron spectroscopy(NAP-XPS), photoemission electron microscopy, and low-energy electron microscopy.Furthermore, CO oxidation under the h-BN cover was also observed by NAP-XPS. The present results indicate that the nanospace under the 2D cover can be used for surface reactions, in which novel surface chemistry may be induced by the nanoconfinement effect.

Intercalation-etching of graphene on Pt(111) in H_2 and O_2 observed by in-situ low energy electron microscopy

Graphene layers are often exposed to gaseous environments in their synthesis and application processes, and interactions of graphene surfaces with molecules particularly H2 and O2 are of great importance in their physico-chemical properties. In this work, etching of graphene overlayers on Pt（111） in H2 and O2 atmospheres were investigated by in-situ low energy electron microscopy. Significant graphene etching was observed in 10-5 Torr H2 above 1O23 K, which occurs simultaneously at graphene island edges and interiors with a determined reaction barrier at 5.7 eV. The similar etching phenomena were found in 10 7 Torr O2 above 973 K, while only island edges were reacted between 823 and 923 K. We suggest that etching of graphene edges is facilitated by Pt-aided hydrogenation or oxidation of edge carbon atoms while intercalation-etching is attributed to etching at the interiors at high temperatures. The different findings with etching in O2 and H2 depend on competitive adsorption, desorption, and diffusion processes of O and H atoms on Pt surface, as well as intercalation at the graphene/Pt interface.

Step-confined thin film growth via near-surface atom migration

Understanding of thin film growth mechanism is crucial for tailoring film growth behaviors,which in turn determine physicochemical properties of the resulting films.Here,vapor-growth of tungsten carbide overlayers on W(110)surface is investigated by real time low energy electron microscopy.The surface growth is strongly confined by surface steps,which is in contrast with overlayer growth crossing steps in a so-called carpet-like growth mode for example in graphene growth on metal surfaces.Density functional theory calculations indicate that the step-confined growth is caused by the strong interaction of the forming carbide overlayer with the substrate blocking cross-step growth of the film.Furthermore,the tungsten carbide growth within each terrace is facilitated by the supply of carbon atoms from near-surface regions at high temperatures.These findings suggest the critical role of near-surface atom diffusion and step confinement effects in the thin film growth,which may be active in many film growth systems.

Continuous wafer-scale graphene on cubic-SiC（O01）

The atomic and electronic structure of graphene synthesized on commercially available cubic-SiC（001）/Si（001） wafers have been studied by low energy electron microscopy （LEEM）, scanning tunneling microscopy （STM）, low energy electron diffraction （LEED）, and angle resolved photoelectron spectroscopy （ARPES）. LEEM and STM data prove the wafer-scale continuity and uniform thickness of the graphene overlayer on SIC（001）. LEEM, STM and ARPES studies reveal that the graphene overlayer on SIC（001） consists of only a few monolayers with physical properties of quasi-freestanding graphene. Atomically resolved STM and micro-LEED data show that the top graphene layer consists of nanometer-sized domains with four different lattice orientations connected through the 〈110〉-directed boundaries. ARPES studies reveal the typical electron spectrum of graphene with the Dirac points close to the Fermi level. Thus, the use of technologically relevant SiC（001）/Si（001） wafers for graphene fabrication repre-sents a realistic way of bridging the gap between the outstanding properties of graphene and their applications.