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Graphene is increasingly explored as a possible platform for developing novel separation technologies (1-19). This interest has arisen because it is a maximally thin membrane that, once perforated with atomic accuracy, may allow ultrafast and highly selective sieving of gases, liquids, dissolved ions and other species of interest (2,9-19). However, a perfect graphene monolayer is impermeable to all atoms and molecules under ambient conditions (1-7): even hydrogen, the smallest of atoms, is expected to take billions of years to penetrate graphene's dense electronic cloud (3-6). Only accelerated atoms possess the kinetic energy required to do this (20,21). The same behaviour might reasonably be expected in the case of other atomically thin crystals (22,23). Here we report transport and mass spectroscopy measurements which establish that monolayers of graphene and hexagonal boron nitride (hBN) are highly permeable to thermal protons under ambient conditions, whereas no proton transport is detected for thicker crystals such as monolayer molybdenum disulphide, bilayer graphene or multilayer hBN. Protons present an intermediate case between electrons (which can tunnel easily through atomically thin barriers (24)) and atoms, yet our measured transport rates are unexpectedly high (4,5) and raise fundamental questions about the details of the transport process. We see the highest room-temperature proton conductivity with monolayer hBN, for which we measure a resistivity to proton flow of about 10 ω [cm.sup.2] and a low activation energy of about 0.3 electronvolts. At higher temperatures, hBN is outperformed by graphene, the resistivity of which is estimated to fall below [10.sup.-3] ω [cm.sup.2] above 250 degrees Celsius. Proton transport can be further enhanced by decorating the graphene and hBN membranes with catalytic metal nanoparticles. The high, selective proton conductivity and stability make one-atomthick crystals promising candidates for use in many hydrogen-based technologies., We have investigated the possibility of proton transport through monocrystalline membranes made from mono- and few-layer graphene, hBN, and molybdenum disulphide (Mo[S.sub.2]). The two-dimensional (2D) crystals (22,23) were obtained by [...]

We report free-standing atomic crystals that are strictly 2D and can be viewed as individual atomic planes pulled out of bulk crystals or as unrolled single-wall nanotubes. By using micromechanical cleavage, we have prepared and studied a variety of 2D crystals including single layers of boron nitride, graphite, several dichalcogenides, and complex oxides. These atomically thin sheets (essentially gigantic 2D molecules unprotected from the immediate environment) are stable under ambient conditions, exhibit high crystal quality, and are continuous on a macroscopic scale. graphene | layered material

X-ray photoemission electron microscopy (X-PEEM) and atomic force microscopy (AFM) are used for examining the morphology and stoichiometry of a model iron oxide magnetic tunneling junction heterostructure. Fe3O4(111) islands and alpha-Fe2O3(0001) terraces are observed in X-PEEM data.

The anomalous Hall effect is analyzed to explain the spatial sensitivity and switching behavior exhibited by the magnetic heterostructures. The magnetic switching of the individual islands taking place in these nanostructures is also demonstrated.

High resolution magnetic force microscopy with in situ applied field is used for determining the switching field distribution (SFD) and hysteresis loop of the islands. It is shown that the coercivity is reduced and the width of the SFD is increased for the smallest islands, suggesting that they would not be well suited to data storage applications.

The composition and magnetic properties of stoichiometric and nonstoichiometric ultrathin iron oxide films grown epitaxially on Al2O3(0001) is characterized. X-ray magnetic circular dichroism XMCD and magnetoresistance (MR) measurements are used for the study.

The magnetic properties of a Cu capped thin film of magnetite (Fe3O4) grown epitaxially on Pt(111) are investigated. The reduced magnetic ordering temperature due to the finite film thickness is the main cause for a reduced magnetic moment in the thin film.