Novel instrumentation developments in X-ray spectroscopy for parallel spectral measurements with soft X-rays are described. The significant performance improvements are achieved utilising Fresnel diffraction from structures built onto the surface of a total external reflection mirror. An array of reflection zone plates was tested as a wavelength-dispersive fluorescence spectrometer for soft X-rays in the energy range of 100–550 eV.

Submitted for the MAR05 Meeting of The American Physical Society Electric Field Effect in Planar Single-Layer Graphene ANDRE GEIM, KOSTYA NOVOSELOV, DA JIANG, YAUN ZHANG, TIM BOOTH, IRINA GRIGORIEVA, University of Manchester, UK, SERGEY MOROZOV, ANATOLY FIRSOV, SERGEY DUBONOS, Institute for Microelectronics Technology, Chernogolovka, Russia — We describe free-standing single-layer crystals of graphene, which are one carbon atom thick but extend over many microns laterally. This two-dimensional fullerene macromolecule is obtained by mechanical exfoliation and allows standard microfabrication procedures, as described in our earlier paper in Science 306, 666 (2004). We have found graphene to be stable under ambient conditions, conductive and of remarkably high quality. Using graphene films, we have fabricated transistor-like devices and studied their properties from room to liquidhelium temperatures. Graphene exhibits a strong ambipolar electric-field effect with room-temperature mobilities of electrons and holes up to ≈10,000 cm2/Vs, which implies ballistic transport over submicron distances. At low temperatures, we have observed pronounced Shubnikov-de Haas oscillations and well-developed plateaulike features, indicating onset of the quantum Hall effect. Graphene is found to be a zero-gap 2D semiconductor. Analysis of the quantum oscillations also indicates the linear, Dirac-like spectrum of its carriers. Andre Geim University of Manchester Date submitted: 01 Dec 2004 Electronic form version 1.4

We report two-dimensional (2D) electron and hole gases induced at the surface of graphite by the electric field effect. The 2D gases reside within a few near-surface atomic layers and exhibit mobilities up to 15 000 and 60 000 cm(2)/V s at room and liquid-helium temperatures, respectively. The mobilities imply ballistic transport on mu m scale. Pronounced Shubnikov-de Haas oscillations reveal the existence of two types of charge carries in both electron and hole gases.

Quantum electrodynamics (resulting from the merger of quantum mechanics and relativity theory) has provided a clear understanding of phenomena ranging from particle physics to cosmology and from astrophysics to quantum chemistry 1 , 2 , 3 . The ideas underlying quantum electrodynamics also influence the theory of condensed matter 4 , 5 , but quantum relativistic effects are usually minute in the known experimental systems that can be described accurately by the non-relativistic Schrödinger equation. Here we report an experimental study of a condensed-matter system (graphene, a single atomic layer of carbon 6 , 7 ) in which electron transport is essentially governed by Dirac's (relativistic) equation. The charge carriers in graphene mimic relativistic particles with zero rest mass and have an effective ‘speed of light’ c * ≈ 10 6 m s -1 . Our study reveals a variety of unusual phenomena that are characteristic of two-dimensional Dirac fermions. In particular we have observed the following: first, graphene's conductivity never falls below a minimum value corresponding to the quantum unit of conductance, even when concentrations of charge carriers tend to zero; second, the integer quantum Hall effect in graphene is anomalous in that it occurs at half-integer filling factors; and third, the cyclotron mass m c of massless carriers in graphene is described by E = m c c * 2 . This two-dimensional system is not only interesting in itself but also allows access to the subtle and rich physics of quantum electrodynamics in a bench-top experiment.

A great deal of attention has recently been focused on a new class of smart materials--so-called left-handed media--that exhibit highly unusual electromagnetic properties and promise new device applications. Left-handed materials require negative permeability micro, an extreme condition that has so far been achieved only for frequencies in the microwave to terahertz range. Extension of the approach described in ref. 7 to achieve the necessary high-frequency magnetic response in visible optics presents a formidable challenge, as no material--natural or artificial--is known to exhibit any magnetism at these frequencies. Here we report a nanofabricated medium consisting of electromagnetically coupled pairs of gold dots with geometry carefully designed at a 10-nm level. The medium exhibits a strong magnetic response at visible-light frequencies, including a band with negative micro. The magnetism arises owing to the excitation of an antisymmetric plasmon resonance. The high-frequency permeability qualitatively reveals itself via optical impedance matching. Our results demonstrate the feasibility of engineering magnetism at visible frequencies and pave the way towards magnetic and left-handed components for visible optics.

We describe monocrystalline graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar electric field effect such that electrons and holes in concentrations up to 1013 per square centimeter and with room-temperature mobilities of ∼10,000 square centimeters per volt-second can be induced by applying gate voltage.

The first successful reconstruction of a synthetic X-ray hologram is reported. A hologram structure was calculated using a specially developed computer software and fabricated on the surface of a Si(111) monocrystal using e-beam lithography and a metal coating technique. A “white” broad-band synchrotron radiation beam from the BESSY bending magnet source was used for the hologram reconstruction. The image was obtained at a photon energy of 8 keV and a distance of 0.5 m from the hologram, placed at a distance of 29 m from the source.

The problem of maximising the relative intensity of the signal optical wave in the course of two-wave mixing was solved taking into account the self-diffraction in a Bi12SiO20 piezoelectric crystal. The maximisation was carried out simultaneously with respect to four parameters: the polarisation (Ψ) and orientation (θ) angles, the crystal thickness d, and the Bragg angle ϕ. It was established that there are two sets of optimal parameters for a Bi12SiO20 crystal at the wavelength of 632.8 nm and for a typical acceptor concentration of 1022 m-3: ϕ ≈ 11°, θ ≈ 39.1°, Ψ ≈ 98.85°, d ≈ 7.11 mm (for the first maximum) and ϕ ≈ 11°, θ ≈ 320.9°, Ψ ≈ 54.15°, d ≈ 7.11 mm (for the second maximum). The dependences of these optimal parameters on the acceptor concentration in the range 1021 — 4 × 1022 m-3 were found. The model proposed for two-wave mixing in the special case of a fixed Bragg angle and the constant visibility approximation improved the agreement between the theoretical results and the known experimental data.

In the present paper we are demonstrated achievement of high spatial resolution for X-ray spectrum of plasma produced by 20 mJ, high-repetition 120 fs laser using a Bragg-Fresnel linear zone plate structure on the mica crystal surface. We had also measured X-ray spectra near resonance line of He-alpha of Mg XI with simultaneously high spectral (up to lambda/Delta lambda = 10000) and spatial (Delta x = 10 mu m) resolution from plasma, heated by such laser, using spectrograph with spherical bent crystal. We demonstrated the important role of inner-shell excitation mechanism for low confinement parameters and propose new excitation channels from highly populated excited states (Li-like and Be-like satellite levels). The collision excitation cross sections for these processes do not decrease with principal quantum number. These channels can be also subject to electron beam excitation. It was shown also the big role of transient effects for Rydberg-Satellites due to a strong three-body recombination into high n-states in the cooling phase. Total spectra simulations are in rather close agreement with experimental results. New 3d(10)4 - 3d(9)41 6f spectral features of Cu-like barium, previously observed as unresolved transition arrays (UTA), are resolved at first time in present paper and enabling plasma diagnostics which were not possible before. The plasma electron density and temperature are found to be in tile ranges: N-e = 5 x 10(21) - 10(22) cm(-3) and kT(e) = 100 - 50 eV, respectively. The generation of intense, collimated monochromatic X-ray beams (lambda similar to 9.5 Angstrom) results are presented too.

A linear zone plate surface structure was created on the surface of mica crystal and used for obtaining spectrally resolved images of 120 fs laser-produced plasma. A linear Fresnel zone structure was optimized on a wavelength lambda = 9.16 Angstrom and has a focal length of f = 5 cm, minimum zone width Delta z(n) = 300 nm, total length l = 10 cm, total width of zone plate 2r(n) = 122.6 mu m.Images of laser-produced plasma in the spectral range 9.12-9.31 Angstrom were obtained For high Z (Lanthanum) element target the size of the X-ray radiation spot was not more than 20 mu m.

Modified electron-beam lithography system and ion-beam etching was used to make elliptical-shaped Bragg-Fresnel multilayer lenses (BFML) in the soft X-Ray range. As substrate for BFML, a Nickel-carbon multilayer X-Ray mirror was used. It consists of 40 double-layers with a period of 4,8 nm having an 11% reflection coefficient at 6 nm wavelength.Special software for E-beam exposure system was developed in order to decrease influence of proximity effect and field distortion.