Unfolding the Challenges To Prepare Single Crystalline Complex Oxide Membranes by Solution Processing.

The ability to prepare single crystalline complex oxide freestanding membranes has opened a new playground to access new phases and functionalities not available when they are epitaxially bound to the substrates. The water-soluble SrAlO (SAO) sacrificial layer approach has proven to be one of the most promising pathways to prepare a wide variety of single crystalline complex oxide membranes, typically by high vacuum deposition techniques. Here, we present solution processing, also named chemical solution deposition (CSD), as a cost-effective alternative deposition technique to prepare freestanding membranes identifying the main processing challenges and how to overcome them.

Chemical synthesis of complex oxide thin films and freestanding membranes.

Oxides offer unique physical and chemical properties that inspire rapid advances in materials chemistry to design and nanoengineer materials compositions and implement them in devices for a myriad of applications. Chemical deposition methods are gaining attention as a versatile approach to develop complex oxide thin films and nanostructures by properly selecting compatible chemical precursors and designing an accurate cost-effective thermal treatment. Here, upon describing the basics of chemical solution deposition (CSD) and atomic layer deposition (ALD), some examples of the growth of chemically-deposited functional complex oxide films that can have applications in energy and electronics are discussed.

Correction to "Chemical Synthesis of LaSrCrO Thin Films for -Type Transparent Conducting Electrodes".

[This corrects the article DOI: 10.1021/acs.chemmater.

Chemical Synthesis of LaSrCrO Thin Films for -Type Transparent Conducting Electrodes.

The imperative need for highly performant and stable -type transparent electrodes based on abundant metals is stimulating the research on perovskite oxide thin films. Moreover, exploring the preparation of these materials with the use of cost-efficient and scalable solution-based techniques is a promising approach to extract their full potential. Herein, we present the design of a chemical route, based on metal nitrate precursors, for the preparation of pure phase LaSrCrO (LSCO) thin films to be used as a -type transparent conductive electrode.

Bendable Polycrystalline and Magnetic CoFeO Membranes by Chemical Methods.

The preparation and manipulation of crystalline yet bendable functional complex oxide membranes has been a long-standing issue for a myriad of applications, in particular, for flexible electronics. Here, we investigate the viability to prepare magnetic and crystalline CoFeO (CFO) membranes by means of the SrAlO (SAO) sacrificial layer approach using chemical deposition techniques. Meticulous chemical and structural study of the SAO surface and SAO/CFO interface properties have allowed us to identify the formation of an amorphous SAO capping layer and carbonates upon air exposure, which dictate the crystalline quality of the subsequent CFO film growth.

Suppression of superconductivity at the nanoscale in chemical solution derived YBaCuO thin films with defective YBaCuO intergrowths.

The analysis of the microstructure and superconducting behavior of chemical solution deposited epitaxial YBaCuO films, with thickness going down to 5 nm has been carried out with the purpose to disclose the behavior of the most common intergrowth in these films, the YBaCuO. The analysis of ultrathin films is a unique opportunity to investigate the superconducting behavior of these nanoscale defects because of the high concentration created as a consequence of the elastic energy associated to the misfit strain. Magnetic susceptibility and X-ray diffraction measurements evidence a strong decrease of the superconducting volume correlated with an increase of the intergrowth volume fraction.

Homogeneous FeO coatings on carbon nanotube structures for supercapacitors.

The combination of carbon nanotubes with transition metal oxides can exhibit complementary charge storage properties for use as electrode materials for next generation energy storage devices. One of the biggest challenges so far is to synthesize homogeneous oxide coatings on carbon nanotube structures preserving their integrity. Here we present the formation of conformal coatings of FeO on vertically aligned carbon nanotubes obtained by atomic layer deposition.

Enhancing Magneto-Ionic Effects in Magnetic Nanostructured Films via Conformal Deposition of Nanolayers with Oxygen Acceptor/Donor Capabilities.

Effective manipulation of the magnetic properties of nanostructured metallic alloys, exhibiting intergrain porosity (i.e., channels) and conformally coated with insulating oxide nanolayers, with an electric field is demonstrated.

Magneto-ionic control of magnetism in two-oxide nanocomposite thin films comprising mesoporous cobalt ferrite conformally nanocoated with HfO.

Advances in nanotechnology require of robust methods to fabricate new types of nanostructured materials whose properties can be controlled at will using simple procedures. Nanoscale composites can benefit from actuation protocols that involve mutual interfacial interactions on the nanoscale. Herein, a method to create nanoscale composite thin films consisting of mesoporous cobalt ferrite (CFO) whose pore walls are nanocoated with HfO2 is presented.

Electrochemical Reduction of Undoped and Cobalt-Doped BiFeO Induced by Water Exposure: Quantitative Determination of Reduction Potentials and Defect Energy Levels Using Photoelectron Spectroscopy.

The interaction of BiFeO and Co-doped BiFeO thin-film surfaces with water vapor is examined using photoelectron spectroscopy. Water exposure results in an upward shift of the Fermi energy, which is limited by the reduction of Bi and Fe in undoped BiFeO and by the reduction of Co in oxidized Co-doped BiFeO. The results highlight the importance of surface potential changes induced by the interaction of solid surfaces with water and the ability of photoelectron spectroscopy to quantitatively determine electrochemical reduction potentials and defect energy levels.

Control of nanostructure and pinning properties in solution deposited YBaCuO nanocomposites with preformed perovskite nanoparticles.

Solution deposited YBaCuO (YBCO) nanocomposites with preformed nanoparticles represent a promising cost-effective approach for superior critical current properties under applied magnetic fields. Nonetheless, the majority of YBCO nanocomposites with high nanoparticle loads (>20%) suffer from nanoparticle coalescence and degraded superconducting properties. Here, we study the influence of nanoparticle concentration (0-25% mol), size (5 nm-10 nm) and composition (BaHfO, BaZrO) on the generation of structural defects in the epitaxial YBCO matrix, key parameter for vortex pinning.

Band Gap Tuning of Solution-Processed Ferroelectric Perovskite BiFe Co O Thin Films.

Ferroelectric perovskite oxides are emerging as a promising photoactive layer for photovoltaic applications because of their very high stability and their alternative ferroelectricity-related mechanism for solar energy conversion that could lead to extraordinarily high efficiencies. One of the biggest challenges so far is to reduce their band gap toward the visible region while simultaneously retaining ferroelectricity. To address these two issues, herein an elemental composition engineering of BiFeO is performed by substituting Fe by Co cations, as a means to tune the characteristics of the transition metal-oxygen bond.

Electrochemical Tuning of Metal Insulator Transition and Nonvolatile Resistive Switching in Superconducting Films.

Modulation of carrier concentration in strongly correlated oxides offers the unique opportunity to induce different phases in the same material, which dramatically change their physical properties, providing novel concepts in oxide electronic devices with engineered functionalities. This work reports on the electric manipulation of the superconducting to insulator phase transition in YBaCuO thin films by electrochemical oxygen doping. Both normal state resistance and the superconducting critical temperature can be reversibly manipulated in confined active volumes of the film by gate-tunable oxygen diffusion.

Electrodeposited Ni-Based Magnetic Mesoporous Films as Smart Surfaces for Atomic Layer Deposition: An "All-Chemical" Deposition Approach toward 3D Nanoengineered Composite Layers.

Mesoporous Ni and Cu-Ni (CuNi and CuNi in at. %) films, showing a three-dimensional (3D) porous structure and tunable magnetic properties, are prepared by electrodeposition from aqueous surfactant solutions using micelles of P-123 triblock copolymer as structure-directing entities. Pores between 5 and 30 nm and dissimilar space arrangements (continuous interconnected networks, circular pores, corrugated mesophases) are obtained depending on the synthetic conditions.

A cobalt(ii)heteroarylalkenolate precursor for homogeneous CoO coatings by atomic layer deposition.

We present a new and efficient cobalt precursor, Co(DMOCHCOCF), to prepare CoO thin films and conformal coatings. In the synthesis of this Co complex, heteroaryl moieties and CF-groups were combined leading to the precursor with high thermal stability and volatility. The suitability of this precursor for ALD deposition was tested on flat silicon substrates and TiO/C nanofibers upon process optimization.

Emerging Diluted Ferromagnetism in High- Superconductors Driven by Point Defect Clusters.

Defects in ceramic materials are generally seen as detrimental to their functionality and applicability. Yet, in some complex oxides, defects present an opportunity to enhance some of their properties or even lead to the discovery of exciting physics, particularly in the presence of strong correlations. A paradigmatic case is the high-temperature superconductor YBaCuO (Y123), in which nanoscale defects play an important role as they can immobilize quantized magnetic flux vortices.

Polarization Switching and Light-Enhanced Piezoelectricity in Lead Halide Perovskites.

We investigate the ferroelectric properties of photovoltaic methylammonium lead halide CH3NH3PbI3 perovskite using piezoelectric force microscopy (PFM) and macroscopic polarization methods. The electric polarization is clearly observed by amplitude and phase hysteresis loops. However, the polarization loop decreases as the frequency is lowered, persisting for a short time only, in the one second regime, indicating that CH3NH3PbI3 does not exhibit permanent polarization at room temperature.

Formation of silicon-based molecular electronic structures using flip-chip lamination.

We report the fabrication of molecular electronic test structures consisting of Au-molecule-Si junctions by first forming omega-functionalized self-assembled monolayers on ultrasmooth Au on a flexible substrate and subsequently bonding to Si(111) with flip-chip lamination by using nanotransfer printing (nTP). Infrared spectroscopy (IRS), spectroscopic ellipsometry (SE), water contact angle (CA), and X-ray photoelectron spectroscopy (XPS) verified the monolayers self-assembled on ultrasmooth Au were dense, relatively defect-free, and the -COOH was exposed to the surface. The acid terminated monolayers were then reacted with a H-terminated Si(111) surface using moderate applied pressures to facilitate the interfacial reaction.