We report the existence of confined electronic states at the (110) and (111) surfaces of SrTiO 3 . Using angle-resolved photoemission spectroscopy, we find that the corresponding Fermi surfaces, subband masses, and orbital ordering are different from the ones at the (001) surface of SrTiO 3 . This occurs because the crystallographic symmetries of the surface and subsurface planes and the effective electron masses along the confinement direction influence the symmetry of the electronic structure and the orbital ordering of the t 2g manifold. Remarkably, our analysis of the data also reveals that the carrier concentration and thickness are similar for all three surface orientations, despite their different polarities. The orientational tuning of the microscopic properties of two-dimensional electron states at the surface of SrTiO 3 echoes the tailoring of macroscopic (e.g., transport) properties reported recently in LaAlO 3 =SrTiO 3 (110) and (111) interfaces, and is promising for searching new types of two-dimensional electronic states in correlated-electron oxides.Two-dimensional electron gases (2DEGs) in transitionmetal oxides (TMOs) present remarkable phenomena that make them unique from a fundamental viewpoint and promising for applications [1,2]. For instance, heterostructures grown on the (001) surface of SrTiO 3 , a TMO insulator with a large band gap of approximately 3.5 eV, can develop 2DEGs showing metal-to-insulator transitions [3], superconductivity [4], or magnetism [5,6]. Recently, 2DEGs at the (111) and (110) interfaces of LaAlO 3 =SrTiO 3 were also reported [7]. The latter showed a highly anisotropic conductivity [8] and a superconducting state spatially more extended than the one at the (001) interface [9]. Interestingly, theoretical works have also predicted that exotic, possibly topological, electronic states might occur at interfaces composed of (111) bilayers of cubic TMOs [10-13], as two (111) planes of transition-metal ions form a honeycomb lattice, similar to the one found in graphene. In this context, the discoveries that 2DEGs can also be created at the bare (001) surfaces of SrTiO 3 [14-16] and KTaO 3 [17,18], and more recently at the (111) surface of KTaO 3 [19], open new roads in the fabrication and study of different types of 2DEGs in TMOs-in particular, using surface-sensitive spectroscopic techniques, which give direct information about the Fermi surface and subband structure of the confined states. The origin of the confinement is attributed to a local doping of the surface region due to oxygen vacancies and/or lattice distortions.Here we show that new types of 2DEGs can be directly tailored at the bare (110) and (111) surfaces of SrTiO 3 . Imaging their electronic structure via angle-resolved photoemission spectroscopy (ARPES), we find that their Fermi surfaces, subband masses, and orbital ordering are different from the ones of the 2DEG at the SrTiO 3 ð001Þ surface [14,15] and the ones predicted for the bulk, being thus uniquely sensitive to the confining crystallographic directi...

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Superconducting nanowires can be fabricated by decomposition of an organometallic gas using a focused beam of Ga ions. However, physical damage and unintentional doping often results from the exposure to the ion beam, motivating the search for a means to achieve similar structures with a beam of electrons instead of ions. This has so far remained an experimental challenge. We report the fabrication of superconducting tungsten nanowires by electron-beam-induced-deposition, with critical temperature of 2.0 K and critical magnetic field of 3.7 T, and compare them with superconducting wires made with ions. This work opens up new possibilities for the realization of nanoscale superconducting devices, without the requirement of an ion beam column.Comment: 5 pages, 4 figure

A soft x-ray spectrometer based on the use of an elliptical focusing mirror and a plane varied line spacing grating is described. It achieves both high resolution and high overall efficiency while remaining relatively compact. The instrument is dedicated to resonant inelastic x-ray scattering studies. We set out how this optical arrangement was judged best able to guarantee performance for the 50 - 1000 eV range within achievable fabrication targets. The AERHA (adjustable energy resolution high acceptance) spectrometer operates with an effective angular acceptance between 100 and 250 μsr (energy dependent) and a resolving power well in excess of 5000 according to the Rayleigh criterion. The high angular acceptance is obtained by means of a collecting pre-mirror. Three scattering geometries are available to enable momentum dependent measurements with 135°, 90°, and 50° scattering angles. The instrument operates on the Synchrotron SOLEIL SEXTANTS beamline which serves as a high photon flux 2 × 200 μm(2) focal spot source with full polarization control.

The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems. Most issues are related to the simultaneous action of high temperatures, corrosive environments and radiation damage. Oxide nanoceramics are a promising class of materials which may benefit from the radiation tolerance of nanomaterials and the chemical compatibility of ceramics with many highly corrosive environments. Here, using thin films as a model system, we provide new insights into the radiation tolerance of oxide nanoceramics exposed to increasing damage levels at 600 °C –namely 20, 40 and 150 displacements per atom. Specifically, we investigate the evolution of the structural features, the mechanical properties, and the response to impact loading of Al2O3 thin films. Initially, the thin films contain a homogeneous dispersion of nanocrystals in an amorphous matrix. Irradiation induces crystallization of the amorphous phase, followed by grain growth. Crystallization brings along an enhancement of hardness, while grain growth induces softening according to the Hall-Petch effect. During grain growth, the excess mechanical energy is dissipated by twinning. The main energy dissipation mechanisms available upon impact loading are lattice plasticity and localized amorphization. These mechanisms are available in the irradiated material, but not in the as-deposited films.

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