Scientific Highlights

Magnetoelectric multiferroics hold great promise for electrical control of magnetism or magnetic control of ferroelectricity. However, single phase ferroelectric materials with a sizeable ferromagnetic magnetization are rare. Here, we demonstrate that a single-phase orthorhombic LuMnO₃ thin film features coexisting magnetic and ferroelectric orders.

Many properties of materials can be changed by varying the interatomic distances in the crystal lattice by applying stress. Ideal model systems for investigations are heteroepitaxial thin films where lattice distortions can be induced by the crystallographic mismatch with the substrate. Here we describe an in situ simultaneous diagnostic of growth mode and stress during pulsed laser deposition of oxide thin films.

In pulsed laser deposition the use of a rectangular or elliptical beam spot with a non 1:1 aspect ratio leads to the so called flip-over effect. Here, the longest dimension of the laser spot results in the shortest direction of plasma plume expansion.

We employ resonant soft x-ray diffraction to individually study the magnetic ordering of the Mn and the Tm sublattices in single-crystalline films of orthorhombic (o−)TmMnO₃. The same magnetic ordering wave vector of (0q0) with q≈0.46 is found for both ionic species, suggesting that the familiar antiferromagnetic order of the Mn ions induces a magnetic order on the Tm unpaired 4f electrons.

In pulsed laser deposition the use of a rectangular or elliptical beam spot with a non 1:1 aspect ratio leads to the so called flip-over effect. Here, the longest dimension of the laser spot results in the shortest direction of plasma plume expansion.

Strain is a leading candidate for controlling magnetoelectric coupling in multiferroics. Here, we use x-ray diffraction to study the coupling between magnetic order and structural distortion in epitaxial films of the orthorhombic (o-) perovskite LuMnO₃. An antiferromagnetic spin canting in the E-type magnetic structure is shown to be related to the ferroelectrically induced structural distortion and to a change in the magnetic propagation vector.

The need for reducing the operating temperature of solid-oxide fuel cells (SOFCs) imposed by cost reduction has pushed significant progress in fundamental understanding of the individual components, as well as materials innovation and device engineering. Proton-conducting oxides have emerged as potential alternative electrolyte materials to oxygen-ion conducting oxides for operation at low and intermediate temperatures.

Plasma chemistry and scattering strongly affect the congruent, elemental transfer during pulsed laser deposition of target metal species in an oxygen atmosphere. Studying the plasma properties of La_0.6Sr_0.4MnO₃, we demonstrate for as grown La_0.6Sr_0.4MnO_3-δ films that a congruent transfer of metallic species is achieved in two pressure windows: ∼10⁻³ mbar and ∼2 × 10⁻¹ mbar.

The electronic structure of a La₂Ti₂O₇-layered perovskite thin film was determined by resonant inelastic X-ray scattering (RIXS) measurements and FEFF calculations. It was found that the empty Ti and La d-band states dominate the conduction band of the structure, whereas the top edge of the valence band is mainly composed of filled O-p states. Furthermore, there is a pronounced overlap between occupied La-p states and O-s states, which are located deeper in the valence band.

Die gleichzeitige Existenz von Magnetismus und Ferroelektrizät in einem Material ist selten. Setzt sich dieser Magnetismus aus mehreren unabhängigen, magnetischen Grundzuständen zusammen, ist das ungewöhnlich. Einer schweizerisch-französischen Zusammenarbeit unter Leitung des Paul Scherrer Instituts ist es gelungen, mehrere magnetische Grundzustände in einem Material zu realisieren und detailliert zu untersuchen.

The physics of the superconducting state in two-dimensional (2D) electron systems is relevant to understanding the high-transition-temperature copper oxide superconductors and for the development of future superconductors based on interface electron systems. But it is not yet understood how fundamental superconducting parameters, such as the spectral density of states, change when these superconducting electron systems are depleted of charge carriers.

Single phase and strained LuMnO₃ thin films are discovered to display coexisting ferromagnetic and antiferromagnetic orders. A large moment ferromagnetism (≈1μB), which is absent in bulk samples, is shown to display a magnetic moment distribution that is peaked at the highly strained substrate-film interface. We further show that the strain-induced ferromagnetism and the antiferromagnetic order are coupled via an exchange field, therefore demonstrating strained rare-earth manganite thin films as promising candidate systems for new multifunctional devices.

The electrical conductivity of dense and nanoporous zirconia-based thin films is compared to results obtained on bulk yttria stabilized zirconia (YSZ) ceramics. Different thin film preparation methods are used in order to vary grain size, grain shape, and porosity of the thin films. In porous films, a rather high conductivity is found at room temperature which decreases with increasing temperature to 120 °C. This conductivity is attributed to proton conduction along physisorbed water (Grotthuss mechanism) at the inner surfaces.

The development of organic electronic requires a non contact digital printing process. The European funded e-LIFT project investigated the possibility of using the Laser Induced Forward Transfer (LIFT) technique to address this field of applications. This process has been optimized for the deposition of functional organic and inorganic materials in liquid and solid phase, and a set of polymer dynamic release layer (DRL) has been developed to allow a safe transfer of a large range of thin films.

With ellipsometry, x-ray diffraction, and resistance measurements we investigated the electric-field effect on the confined electrons at the LaAlO₃/SrTiO₃ interface. We obtained evidence that the localization of the electrons at negative gate voltage is induced, or at least enhanced, by a polar phase transition in SrTiO₃ which strongly reduces the lattice polarizability and the subsequent screening. In particular, we show that the charge localization and the polar order of SrTiO₃ both develop below ∼50  K and exhibit similar, unipolar hysteresis loops as a function of the gate voltage.

Laser-induced forward transfer (LIFT) is a versatile organic light-emitting diode (OLED) pixel deposition process, but has hitherto been applied exclusively to polymeric materials. Here, a modified LIFT process has been used to fabricate small molecule Alq₃ organic light-emitting diodes (SMOLEDs). Small molecule thin films are considerably more mechanically brittle than polymeric thin films, which posed significant challenges for LIFT of these materials.

In conjunction with the increasing availability of cost-efficient laser units during the recent years, laser-based micromachining techniques have been developed as an indispensable industrial instrument of ‘‘tool-free’’ high-precision manufacturing techniques for the production of miniaturized devices made of nearly every type of materials. Laser cutting and drilling, as well as surface etching, have grown meanwhile to mature standard methods in laser micromachining applications where a well-defined laser beam is used to remove material by laser ablation. As an accurately triggerable nonmechanical tool, the ablating laser beam directly allows a subtractive direct-write engraving of precise microscopic structure patterns on surfaces, such as microchannels, grooves, and well arrays, as well as for security features. Therefore, laser direct-write (LDW) techniques imply originally a controlled material ablation to create a patterned surface with spatially resolved three-dimensional structures, and gained importance as an alternative to complementary photolithographic wet-etch processes. However, with more extended setups, LDW techniques can also be utilized to deposit laterally resolved micropatterns on surfaces, which allows, in a general sense, for the laser-assisted ‘‘printing’’ of materials.

The physical mechanisms responsible for the formation of a two-dimensional electron gas at the interface between insulating SrTiO₃ and LaAlO₃ have remained a contentious subject since its discovery in 2004. Opinion is divided between an intrinsic mechanism involving the build-up of an internal electric potential due to the polar discontinuity at the interface between SrTiO₃ and LaAlO₃, and extrinsic mechanisms attributed to structural imperfections.

Patterned deposition of polymer light-emitting diode (PLED) pixels is a challenge for electronic display applications. PLEDs have additional problems requiring solvent orthogonality of different materials in adjacent layers. We present the fabrication of a PLED pixel by the sequential deposition of two different layers with laser-induced forward transfer (LIFT), a “dry” deposition technique. This novel use of LIFT has been compared to “normal” LIFT, where all the layers are transferred in a single step, and a conventional PLED fabrication process.

X-ray near edge absorption spectroscopy was used to probe the electronic structure of multiferroic orthorhombic LuMnO₃ polycrystalline samples and strained, twin-free orthorhombic (1–10) LuMnO₃ films grown by pulsed laser deposition on (1–10) YAlO₃ substrates. For all o-LuMnO₃ samples x-ray near edge absorption spectroscopy spectra reveal that the pre-edge structure is influenced by the increase in MnO6 distortion as a result of the smaller Re-ion or film strain. Furthermore there is clear evidence of anisotropic Mn-O bonding and Mn orbital ordering along the c- and [110] direction. The experimental film and bulk data are in agreement with ab initio simulations.

An optimized laser-induced forward transfer (LIFT) technique has been used to fabricate tri-color organic light-emitting diode (OLED) pixels. At reduced pressures, and with a defined donor-receiver gap, patterned depositions of polyfluorene-based OLED pixels have been achieved. OLED pixel functionality has been demonstrated and compared with devices made using conventional deposition techniques. In addition, improved functionality has been obtained by coating the cathode with an electron-injecting layer, a process not possible using conventional OLED fabrication techniques. The OLED pixels fabricated by LIFT reach efficiencies on the range of conventionally fabricated devices and even surpass them in the case of blue pixels.