Nanofilm Allotrope and Phase Transformation of Ultrathin Bi Film on Si(111)7X7

金沢大学理学部Nanofilm allotrope and phase transformation of ultrathin Bi film on Si(111)-7 × 7 were analyzed using scanning tunneling microscopy and electron diffraction experiments. It was observed that this pseudocubic {012}-oriented allotrope is stable up to four atomic layers at room temperature. The entire volume of the film started to transform into a bulk single-crystal (001) phase, as the bulk contribution in the cohesion became dominant, above the critical thickness. It was proposed that the allotrope consists of black phosphorus-like puckered layers stabilized by saturating all the pz dangling bonds in the film, based on ab initio calculations

Ferromagnetic GaMnAs/GaAs superlattices - MBE growth and magnetic properties

We have studied the magnetic properties of (GaMnAs)m/(GaAs)n superlattices with magnetic GaMnAs layers of thickness between 8 and 16 molecular layers (ML) (23-45 \AA), and with nonmagnetic GaAs spacers from 4 ML to 10 ML (11-28 \AA). While previous reports state that GaMnAs layers thinner than 50 \AA are paramagnetic in the whole Mn composition range achievable using MBE growth (up to 8% Mn), we have found that short period superlattices exhibit a paramagnetic-to-ferromagnetic phase transition with a transition temperature which depends on both the thickness of the magnetic GaMnAs layer and the nonmagnetic GaAs spacer. The neutron scattering experiments have shown that the magnetic layers in superlattices are ferromagnetically coupled for both thin (below 50 \AA) and thick (above 50 \AA) GaMnAs layers.Comment: Proceedings of 4th International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology, September 23 - 28 (2001), Warszawa, Poland, to appear in Thin Solid Films. 24 pages, 8 figure

Scanning tunneling microscopy on epitaxial bilayer graphene on ruthenium (0001)

The atomic structure of epitaxial single and bilayer graphene on Ru(0001) was studied by scanning tunneling microscopy (STM). High-resolution imaging of the surface of single layer graphene shows a moiré with pronounced buckling and broken A/B carbon sublayer symmetry due to a strong interaction with the metal substrate. The top sheet of bilayer graphene is largely unperturbed by residual interactions with the substrate. Screened from the metal substrate, it shows the hallmarks of freestanding monolayer graphene: a honeycomb structure with equivalent carbon sublattices imaged in STM and a linear dispersion of bands near the Dirac point

In-situ spectro-microscopy on organic films: Mn-Phthalocyanine on Ag(100)

Metal phthalocyanines are attracting significant attention, owing to their potential for applications in chemical sensors, solar cells and organic magnets. As the electronic properties of molecular films are determined by their crystallinity and molecular packing, the optimization of film quality is important for improving the performance of organic devices. Here, we present the results of in situ low-energy electron microscopy / photoemission electron microscopy (LEEM/PEEM) studies of incorporation-limited growth [1] of manganese-phthalocyanine (MnPc) on Ag(100) surfaces. MnPc thin films were grown on both, bulk Ag(100) surface and thin Ag(100)/Fe(100) films, where substrate spin-polarized electronic states can be modified through tuning the thickness of the Ag film [2]. We also discuss the electronic structure and magnetic ordering in MnPc thin films, investigated by angle- and spin-resolved photoemission spectroscopy

Low-energy electron microscope study of tobacco mosaic viruses

Virus microscopy – or perhaps more proper, ‘nanoscopy’, since their typical dimensions are on the nanometer scale – is crucially important for their identification and study. The required high spatial resolution can be achieved by transmission electron microscopy (TEM), but at the expense of using high-energy (typically 50 - 400 keV) electrons that cause substantial radiation damage. A less invasive variant of virus electron microscopy would be highly desirable. Here, we present the first low-energy electron microscope (LEEM) observation of viruses. SrRuO3 films and Nb-doped SrTiO3 bulk single crystals are introduced as excellent new substrates for LEEM studies. High-quality images of the tobacco mosaic virus (TMV) are obtained with electrons at just a few eV, or even without reaching the surface. LEEM offers easy sample preparation, tens of high-resolution images per second, and no radiation damage. With additional capabilities such as spectroscopy and diffraction, it is a promising technique for the study of viruses and other biological nano-objects

A mathematical model of solid-state dewetting of barium thin films on

Solid state dewetting occurs when a thin solid film is heated. The temperature of dewetting depends on the thickness of the film; dewetting can be observed in the range of 1∕3 to 1∕2 of the bulk melting temperature. While remaining solid, the film behaves in a manner similar to liquids dewetting and agglomerating to forming islands or droplets. One of the possible mechanisms is the conversion of a metastable thin film geometry into a more stable form. Heating the metastable film gives the film atoms higher mobility, and the films retract, dewetting the surface. This atomic motion can be restricted due to surface anisotropy. We present in situ emission microscopy observations of barium thin films deposited onto W(112) by thermal evaporation. From the modeling viewpoint, the evolution of the film in this system could be divided in four stages: (i) the nucleation and growth of the thin film as a simply connected region; (ii) formation of droplets/islands/hillocks; (iii) nucleation of holes; (iv) evolution of the components of the disconnected film to their equilibrium state. We present a continuum model that is qualitatively consistent with the evolution of the film observed at the initial stage of the experiment and discuss the later stages of the evolution of surface structures

Extreme Responses to Virtual Environment Exposure

An emetic response (a.k.a. vomiting) is certainly one of the most extreme responses to virtual environment (VE) exposure. This unpleasant response is thankfully quite rare (approximately 1 -2%) but when it does occur, the individuals afflicted are generally quite distraught that something that looks akin to watching television can have such adverse consequences. This paper examines the experiences of individuals who have had an emetic response during or after VE exposure. An effort is made to both identify factors that may predict who vomits and characterize the extent of symptoms they experience. Results indicate that VE system designers may be able to reduce emetic response rates by streamlining user movement control and simplifying visual scene content. The results also indicate it may prove difficult with current measures to predict who will experience an emetic response