Catalin Harnagea

Institut National de la Recherche Scientifique | INRS · Energy, Materials and Telecommunications Research Centre

Multiferroic thin films are a promising class of multifunctional materials, since they allow the integration of multiple functionalities within a single device. In order to overcome the scarcity of single phase multiferroics, it is crucial to develop novel multiferroic heterostructures, combining good ferroelectric and ferromagnetic properties as w...

We report on the hydrothermal synthesis of high quality polycrystalline zinc oxide nanorod arrays grown on indium tin oxide substrates. We observe a clear effect of the nucleation and growth rates on the morphology and orientation of the nanorod arrays, with a predominance of the polycrystalline hexagonal wurtzite structure and preferential c-axis...

Conversion of clean solar energy to chemical fuels is one of the promising and up-and-coming applications of metal–organic frameworks. However, fast recombination of photogenerated charge carriers in these frameworks remains the most significant limitation for their photocatalytic application. Although the construction of homojunctions is a promisi...

We study the photoactive properties of poly [N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT): [6,6]-Phenyl-C71-butyric acid methyl ester (PCBM) thin films under ultraviolet irradiation as well as their photo-oxidation, thermal and electrical properties. We compare their stability and performance with...

We study the photoactive properties of poly [N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT): [6,6]-Phenyl-C71-butyric acid methyl ester (PCBM) thin films under ultraviolet irradiation as well as their photo-oxidation, thermal and electrical properties. We compare their stability and performance with...

Four different functional properties at room temperature were found in Ba12Fe28Ti15O84 quaternary ferrite ceramics: a thermoelectric character with a prominent Seebeck coefficient of -400 μV/K, a strong ferrimagnetic character and weak magnetoresistivity, non-linear dielectric character (tunability) and ferro/piezoelectric response. The complex cry...

Achieving high oxygen evolution reaction (OER) activity while maintaining performance stability is a key challenge for designing perovskite structure oxide OER catalysts, which are often unstable in alkaline environments transforming into an amorphous phase. While the chemical and structural transformation occurring during electrolysis at the elect...

The photoelectric properties of multiferroic double-perovskite Bi2FeCrO6 (BFCO), such as above-bandgap photovoltages, switchable photocurrents and bulk photovoltaic effect, have recently been explored for potential applications in solar technology. Here we report the fabrication of photoelectrodes based on n−type ferroelectric (FE) semiconductor BF...

Inorganic ferroelectric perovskites are attracting attention for the realization of highly stable photovoltaic cells with large open-circuit voltages. However, the power conversion efficiencies of devices have been limited so far. Here, we report a power conversion efficiency of ~4.20% under 1 sun illumination from Bi–Mn–O composite thin films with...

Perovskite multiferroic oxides are promising materials for the realization of sensitive and switchable photodiodes, due to their favorable band gap (< 3.0 eV), high absorption coefficient and tunable internal ferroelectric polarization. A high speed switchable photodiode based on multiferroic Bi2FeCrO6 (BFCO)/SrRuO3 (SRO) layered heterojunction was...

High-quality Ba2NdFeNb4O15-based nanocomposite films were grown on Pt/MgO(100) single crystalline substrates. The c-oriented epitaxial films have the unit cell rotated in the plane by ± 18.5° with respect to that of the substrate. The room temperature ferroelectric properties of the films were demonstrated at both the macroscopic and the microscopi...

Highly c-oriented Ba2LnFeNb4O15-based multiferroic composite films with the lanthanide ion Ln = Eu³⁺, Sm³⁺ and Nd³⁺, have been grown by puled laser deposition on platinum-coated (0 0 1)-oriented silicon substrates. Investigation of the films functional properties demonstrated that both ferroelectricity and magnetism, originating respectively from t...

Multiferroic Ba2NdFeNb4O15-based composite thin films have been deposited on Pt/Si(100) substrates by pulsed laser deposition. Structural investigation demonstrated the achievement of highly c-oriented thin films of Ba2NdFeNb4O15 upon optimization. Macroscopic ferroelectric hysteresis loops showed that ferroelectric properties were considerably imp...

Epsilon ferrite (ε-Fe2O3) is a metastable phase of iron(III) oxide, intermediate between maghemite and hematite. It has recently attracted interest because of its magnetocrystalline anisotropy, which distinguishes it from the other polymorphs, and results in a gigantic coercive field and a natural ferromagnetic resonance frequency in the THz range....

Nanostructured magnetic materials with well-defined magnetic anisotropy are very promising as building blocks in spintronic devices that operate at room temperature. Here we demonstrate the epitaxial growth of highly oriented Fe3O4 nanorods on a SrTiO3 substrate by hydrothermal synthesis without the use of a seed layer. The epitaxial nanorods showe...

We demonstrate the growth and characterization of an array of ferroelectric nanowires for photoelectrochemical (PEC) hydrogen production. The photoelectrodes are made of vertically aligned one-dimensional nanowires of the “classic” ferroelectric perovskite KNbO3 grown epitaxially on a Nb-doped SrTiO3 substrate. The charge transfer properties of the...

Photovoltaic devices made of ferroelectric films are being widely studied, due to the efficient charge separation driven by the internal polarization as well as above-bandgap generated photovoltages. These features may enable power conversion efficiencies (PCE) exceeding the Shockley–Queisser limit, which characterizes conventional semiconductor-ba...

High-quality thin films of Ba2EuFeNb4O15 have been epitaxially grown on MgO(001) substrates by pulsed laser deposition. Structural investigations indicate the successful growth of the desired c-oriented phase, and showed four growth variants with the thin film unit cell rotated in-plane by an angle of ±18.4° and ±31° with respect to the MgO substra...

Hysteresis loops characterize a wide variety of behaviors in fields ranging from physics and chemistry to economics and sociology. In particular, they represent the main characteristic of ferroic materials such as ferromagnetic and ferroelectric, which, in recent years, have attracted much interest due to their multifunctional properties. Although...

We report an external solar power conversion efficiency of ∼1.43% in BiFeO3(BFO)/BiMnO3(BMO) bilayer thin films. Both films are epitaxially grown on (111) oriented niobium doped SrTiO3 (NSTO) single crystal substrates by pulsed laser deposition. By illuminating the BFO/BMO films under 1 Sun (AM 1.5 G), we found a remarkably high fill factor of ∼0.7...

The photoluminescence (PL) enhancement of a Ag nanoparticle and near-infrared quantum dots (QD) plasmon/fluorophore system was investigated. Different enhancement mechanisms were obtained by tuning surface plasmon resonance of the Ag film and PL of the QDs. A maximum enhancement factor of 2.8 was achieved.

Surface morphology of 1018 steel samples was studied after early stages of gaseous nitriding using AFM technique. Oscillation in measured roughness and gas/solid interface area values at different stages of process has been reported. The amplitude and period of such oscillation depends on initial surface finishing.

Multiferroic films are increasingly being studied for applications in solar energy conversion because of their efficient ferroelectric polarization-driven carrier separation and above-bandgap generated photovoltages, which in principle can lead to energy conversion efficiencies beyond the maximum value (∼34%) reported in traditional silicon-based b...

Nosocomial infections (Nis) are a major concern for public health. As more and more of the pathogens responsible for these infections are antibiotic resistant, finding new ways to overcome them is a major challenge for biomedical research. We present a method to reduce Nis spreading by hindering bacterial adhesion in its very early stage. This is a...

We report an external solar power conversion efficiency of ~0.1% in Bi-Mn-O thin films grown onto (111) oriented Niobium doped SrTiO3 (STO) single crystal substrate by pulse laser deposition (PLD). The films contain BiMnO3 (BMO) and Mn3O4 (MO) phases, which both grow epitaxially. The growth conditions were tailored to obtain films with different Bi...

Anisotropic nanostructures such as nanowires (NWs)/nanotubes and nanometer-sized islands are the subject of intense research efforts due to several interesting phenomena observed to occur in confined geometries with a high aspect ratio and/or reduced size. Understanding and controlling the mechanical and electromechanical behaviors of these nanostr...

A novel technique to extract nacre tablets (bricks) from molluskan shells using 'soft energy' ionic liquid based dissolution of the organic material (mortar) between the tablets rather than using high energy and potentially tablet-damaging ball milling processing. The tablets isolated from this 'unzipping' of the shell in the ionic liquid n-butyl-3...

The structure of La-doped bismuth titanate (BLT), Bi3.25La0.75Ti3O12, is investigated with atomic resolution high-angle annular dark field (HAADF) scanning transmission electron microscopy. The images reveal evidence of the tilting of TiO6 octahedra within the perovskite-like layers of the BLT unit cell. The tendency of La ions to substitute Bi ion...

We report the ferroelectric properties of single-crystalline BiFeO3 nanowires using piezoresponse force microscopy (PFM). The nanowires, synthesized by a hydrothermal approach, have a rhombohedral perovskite structure and a preferential growth of the (211) crystallographic plane perpendicular to the wire axis, as revealed by x-ray and electron diff...

We report on the elastic and piezoresistive properties of individual epitaxial Si-NWs grown on n-doped Si(111) by pulsed laser deposition. Using scanning probe microscopy, we obtained a Young's modulus between 82 and 900 GPa for the nanowires, unaffected by the nanowire shape. A relative resistivity change is observed in the prestrained (curved) Si...

We report the control of the growth mode of Bi(2)FeCrO(6) thin and ultrathin films by either tuning the pulsed laser deposition parameters or by using a buffer layer. The films are epitaxial and the heterostructures exhibit very smooth interfaces, thus eliminating the main obstacle in the realization of tunnel junctions. By characterizing the funct...

This paper explores in depth the partially switched states of ferroelectrics, through macroscopic polarization measurements in conjunction with piezoresponse force microscopy, x-ray diffraction and dielectric characterization, with the ultimate purpose to explore their usefulness for unconventional multiple-value nonvolatile memory applications. We...

Diatoms have ordered three dimensional porous exoskeletons (frustules) comprised primarily of amorphous silica which can be used as templates for materials applications. Hydrolysis of titanium(IV) isopropoxide (TIP) in the presence of surface bound poly(4-vinyl pyridine) or citric acid results in the formation of anatase on the surface after calcin...

We report recent developments in the growth and characterization of epitaxial Bi(2)FeCrO(6) (BFCO) thin films. The body of experimental data stemming mostly from our investigations, and also considering the few available reports from other groups, allows us to explain the origin(s) of the thickness dependence of the multiferroic properties observed...

Spider silk is a fascinating natural composite material. Its combination of strength and toughness is unrivalled in nature, and as a result, it has gained considerable interest from the medical, physics, and materials communities. Most of this attention has focused on the one to tens of nanometer scale: predominantly the primary (peptide sequences)...

The combination of nanostenciling with pulsed laser deposition (PLD) provides a flexible, fast approach for patterning the growth of Ge on Si. Within each stencilled site, the morphological evolution of the Ge structures with deposition follows a modified Stranski-Krastanov (SK) growth mode. By systematically varying the PLD parameters (laser repet...

Here we report on the piezoelectric and ferroelectric properties of individual one-dimensional objects made of Bi4Ti3O12 (BiT). The nanorods and nanowires investigated in this study were fabricated by a two-step process: (1) preparation of reactive templates using hydrothermal-like synthesis and colloidal chemistry and (2) transformation of the rea...

We report a large photovoltaic (PV) effect in multiferroic Bi ₂ FeCrO ₆ (BFCO) films under monochromatic illumination at 635 nm with an intensity of 1.5 mW   cm ^-2 . These multiferroic films exhibit a large photocurrent at zero bias voltage and an open-circuit voltage of about 0.6 V. A high PV power conversion effic...

Arbitrary patterns of heteroepitaxial multiferroic Bi2FeCrO 6 nanostructures are fabricated by pulsed laser deposition using a simple nanostencil approach. The crystal orientation and the shape of the epitaxial nanostructures are controlled by the orientation of the niobium-doped SrTiO3 substrates. Using advanced characterization techniques, it is...

We report on an imaging method for ferroelectric domains by noncontact atomic force microscopy with dipole-molecule decorated tips. The Coulombic tip-sample interaction is revealing the domains monitored as an additional topography contribution. As proof of concept, we present agreement between numerical simulations and experiments on antiparallel...

Epitaxial [γ -Fe ₂ O ₃– BiFeO ₃]/ Bi _3.25 La _0.75 Ti ₃ O ₁₂ and Bi _3.25 La _0.75 Ti ₃ O ₁₂/[γ -Fe ₂ O ₃– BiFeO ₃] composite bilayers were grown on SrRuO ₃ coated (111) SrTiO ₃...

A fundamental issue in the physics of ferroelectric memories and piezoelectric devices is to study how their properties scale with the size of the ferroelectric structure. In this work we present results concerning the ferroelectric behavior of structures with lateral sizes in the range 100 nm to 1 μm. The ferroelectric characterization was achieve...

Anisotropies of the properties of the bismuth-layered perovskite SrBi 2 Ta 2 O 9 (SBT) have been investigated using epitaxial thin films grown by pulsed laser deposition both on conducting Nb-doped SrTiO 3 (STO) single crystal substrates and on Si(100) substrates. It has been found that the three-dimensional epitaxy relationship SBT(001)||STO(001);...

Fascia tissue is rich in collagen type I proteins and can be imaged by second harmonic generation (SHG) microscopy. While identifying the overall alignment of the collagen fibrils is evident from those images, the tridimensional structural origin for the observation of SHG signal is more complex than it apparently seems. Those images reveal that th...

Ferroelectric nanostructures have been fabricated by self-assembly, using the high temperature instability of ultra thin films. Lead zirconate titatnate (PZT) structures, as small as 20 nm lateral size with a height of 9 nm, have been fabricated on (100) SrTiO3 substrates. The shapes and sizes of the ferroelectric structures could be tuned within a...

The piezoelectric properties of single collagen type I fibrils in fascia were imaged with sub-20 nm spatial resolution using piezoresponse force microscopy. A detailed analysis of the piezoresponse force microscopy signal in controlled tip-fibril geometry revealed shear piezoelectricity parallel to the fibril axis. The direction of the displacement...

We present studies on parallel nanoscale patterning of piezoelectrics/ferroelectrics via deposition through a nanostencil. Unlike other processes reported for oxide nanostructuring, we selectively deposit the material, directly, by interposing a nanosieve between the substrate and the deposition source. We show that this selective deposition can be...

Multiple NaNbO3 nanoplates are created within Nb2O5 nanotubes forming a unique class of heterostructure nanotubes combining ferroelectric and semiconducting nanomaterials. Local piezoelectric studies on NaNbO3 nanoplates show clear ferroelectric behavior (see figure), while the semiconductive properties of the host Nb2O5 nanotubes allows for switch...

Bi2FeCrO6 thin films were epitaxially grown by pulsed laser deposition on (100)-oriented LaAlO3, (LaAlO3)0.3(Sr2LaTaO6)0.7 and SrTiO3 single crystalline substrates with and without epitaxial CaRuO3 buffered layer. The in-plane compressive strain induces monoclinic distortion of the Bi2FeCrO6 lattice cell. The strain originates from lattice mismatch...

Atomic resolution high-angle annular dark-field imaging of La-doped bismuth titanate (BLT), Bi _3.25 La _0.75 Ti ₃ O ₁₂ , has been carried out with an aberration-corrected transmission electron microscope. The HAADF image revealed the presence of defects in the [ Bi ₂ O ₂]²⁺...

The possible existence of a new kind of ferroelectric order and the need to explore domain arrangement in ferroelectric nanostructures has stimulated an increasing activity on the growth of ferroelectric nanowires. In the present study, single crystal BaTiO3 nanowires with tetragonal structure were obtained by an original solid-state process using...

We report the growth and the characterization of novel Ce2.2Bi0.8Fe5O12-(Ce:BiIG) epitaxial thin films. By using a magneto-optical set-up in a transmission geometry, we recorded the highest Faraday rotation ever reported for magneto-optical garnet thin films, i.e. 0.55 degrees/mum @1550 nm.

This article compares and contrasts information obtained, using transmission electron microscopy (TEM) and piezo-force microscopy (PFM), on domain configurations adopted in single crystal lamellae of BaTiO3, that had been cut directly from bulk using a focused ion beam microscope with top and bottom surfaces parallel to {100}pseudocubic. Both forms...

The multiferroic behavior of epitaxial γ-Fe2O3–BiFeO3 (composite)/Bi3.25La0.75Ti3O12 bi-layered heterostructures grown on SrRuO3/SrTiO3 (1 1 1) substrates has been studied using piezoresponse force microscopy, magnetic force microscopy and magnetometry. The ferroelectric domain structure is ascribed to the BiFeO3 phase while the magnetism originate...

Ce and Bi comodified iron garnet ( Ce _2.2 Bi _0.8 Fe ₅ O ₁₂) thin films for magneto-optic applications were epitaxially grown on a (111)-oriented Gd ₃ Ga ₅ O ₁₂ substrate by pulsed laser deposition. We found that epitaxial film quality could be achieved under a low-pressure...

Experimental results on Bi2FeCrO6 (BFCO) epitaxial films deposited by laser ablation on SrTiO3 substrates are presented. It has been theoretically predicted using first-principles density functional theory that BFCO is ferrimagnetic (with a magnetic moment of 2muB per formula unit) and ferroelectric (with a polarization of ~80 microC/cm2 at 0K). Th...

The influence of the deposition pressure (P O ₂) and substrate temperature (T_S) during the growth of Bi ₂ FeCrO ₆ thin films grown by pulsed laser deposition has been investigated. It is found that the high volatility of Bi makes the deposition very difficult and that the growth of pure Bi ₂ Fe...

Tin oxide nanowires (NWs) exhibit interesting electronic properties, which can be harnessed for applications in nanoelectronic devices and sensors. Oriented single crystalline tin oxide NWs were grown at 45 degrees from a titanium dioxide substrate. Their elastic properties were investigated in a two-point geometry using an atomic force microscope...

We report on the growth and characterization of novel Ce2.2Bi0.8Fe5O12-(Ce:BiIG) epitaxial thin films fabricated via Pulsed Laser Deposition. Our results suggest the highest Faraday rotation ever obtained in magneto-optical garnet thin films (0.55degrees/µm, @1550 nm).

of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

We summarise here our efforts toward the fabrication and characterisation of ferroelectric and multiferroic films and structures. First, we discuss the challenges related with the fabrication and characterisation of nanostructures of functional complex oxides. In particular, to demonstrate the functionality of our films and especially of our struct...

Multiferroic properties of γ-Fe2O3–BiFeO3/Bi3.25La0.75Ti3O12 epitaxial composite bi-layers grown on SrRuO3/SrTiO3(1 1 1) are compared with the properties of single phase BiFeO3 and Bi3.25La0.75Ti3O12 thin films. The composite bi-layers show well-saturated hysteresis loops with a low coercive field, a high fatigue resistance and high saturation magn...

Infrared reflectance spectra of an epitaxial Bi2FeCrO6 thin film prepared by pulsed laser deposition on LaAlO3 substrate were recorded between 10 and 900 K. No evidence for a phase transition to the paraelectric phase was observed, but some phonon anomalies were revealed near 600 K. Most of the polar modes exhibit only a gradual softening, which re...

Organic light emitting field effect transistors based on 2-(4-pentylstyryl)tetracene are able to operate in ambient air and have a shelf lifetime of several months. The Royal Society of Chemistry 2008.

The existence of unexpected magnetic ordering at room temperature in the multiferroic double perovskite Bi2FeCrO6 (BFCO) thin film synthesized by conventional pulsed laser deposition (PLD) has been attributed to the exchange interaction between the alternating planes of Fe and Cr cations along [111] direction.[1] The properties of this material hav...

The properties of epitaxial Bi₂FeCrO6 thin films, recently synthesized by pulsed laser deposition, have partially confirmed the theoretical predictions (i.e., a magnetic moment of 2 mubeta per formula unit and a polarization of ~80 muC/cm² at 0 K). The existence of magnetic ordering at room temperature for this material is an...

BaTiO3–(Ni0.5Zn0.5)Fe2O4 composites prepared by co-precipitation were investigated. The macroscopic magnetic properties derived from the magnetic phase (low coercivity, almost no M(H) hysteretic behavior and high permeability) are preserved in the composite. The dielectric properties are strongly influenced by interface phenomena (Maxwell-Wagner),...

Multifunctional BiFeO3 (BFO), BiCrO3 (BCO), and BFO/BCO heteroepitaxial films with good ferroelectric properties were grown by pulsed laser deposition on epitaxial CaRuO3-coated (100)-oriented LaAlO3 and (LaAlO3)0.3(Sr2LaTaO6)0.7. The in-plane compressive strain induces a tetragonal crystal structure in both BFO and BCO films in the BFO/BCO bilayer...

The authors combine nanostenciling and pulsed laser deposition to pattern germanium (Ge) nanostructures into desired architectures. They have analyzed the evolution of the Ge morphology with coverage. Following the formation of a wetting layer within each area defined by the stencil’s apertures, Ge growth becomes three dimensional and the size and...

of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Florida, USA, August 5 – August 9, 2007

Bi₂Fe_xCr_yO₆ epitaxial films have been grown on (100)-and (111)-oriented SrTiO₃ substrates using dual crossed beam pulsed laser deposition (DCB-PLD). The films crystal structure, chemical composition ferroelectric and magnetic properties were investigated and are reported.

Epitaxial thin films of Bi2FeCrO6 have been synthesized by pulsed laser deposition on SrRuO3 on (100)- and (111)-oriented SrTiO3 substrates. Detailed X-ray diffraction and cross-section transmission electron microscopy analysis revealed a double perovskite crystal structure of the Bi2FeCrO6 epitaxial films very similar to that of BiFeO3 along with...

Usually ferroelectric thin films are deposited by pulsed laser deposition (PLD) at elevated substrate temperatures, in order to obtain a good crystalline quality. Here we report the fabrication of ferroelectric BaTiO3 and BiFeO3 structures by room-temperature PLD combined with post-deposition annealing, and their ferroelectric characterization. A m...

Good quality strontium ruthenate (SrRuO3) thin continuous films (15 to 125 nm thick) have been synthesized on silicon (100) substrates by room temperature pulsed laser deposition under vacuum followed by a post-deposition annealing, a route unexplored and yet not reported for SrRuO3 film growth. The presence of an interfacial Sr2SiO4 layer has been...

Di-phase ceramic composites 0.50BaTiO3–0.50Ni0.5Zn0.5Fe2O4 with limited reaction at interfaces prepared by two methods: (i) mixing BaTiO3 and Ni0.5Zn0.5Fe2O4 powders and (ii) co-precipitation of Fe, Ni, Zn salts in solutions containing BaTiO3 powders, are comparatively analysed. Homogeneous microstructures with higher density and better mixing of t...

We present here experimental results obtained on Bi2FeCrO6 (BFCO) epitaxial films deposited by laser ablation directly on SrTiO3 substrates. It has been theoretically predicted, by Baettig and Spaldin, using first-principles density functional theory that BFCO is ferrimagnetic (with a magnetic moment of 2 Bohr magneton per formula unit) and ferroel...

Bismuth ferrite BiFeO3 is a multiferroic material, exhibiting both electric and magnetic ordering at room temperature, properties which make it a promising material for use in novel device fabrication. We report here the successful fabrication of BiFeO3 thin films and of isolated micron-sized structures by pulsed laser deposition. We present the st...

The authors report the structural and physical properties of epitaxial Bi ₂ Fe Cr O ₆ thin films on epitaxial Sr Ru O ₃ grown on (100)-oriented Sr Ti O ₃ substrates by pulsed laser ablation. The 300 nm thick films exhibit both ferroelectricity and magnetism at room temperature with a maximum dielectric po...

We present how various features drawn in a miniature shadow mask (nanostencil) can be efficiently transferred to a surface in the form of three-dimensional nanostructures of metals (Pt, Cr), semiconductors (Ge), and complex oxides (e.g., BaTiO₃) by room temperature pulsed laser deposition. Selective deposition is obtained by interposing...

We present how various features drawn in a miniature shadow-mask (nanostencil) can be efficiently transferred to a surface in the form of 3D nanostructures of metals (Pt, Cr), semiconductors (Ge) or complex oxides (e.g. BaTiO 3 ) by room temperature pulsed laser deposition (PLD) and stenciling. Using the proposed method, there is no aggressive inte...

Theoretical models for small ferroelectric particles predict a progressive decrease of the Curie temperature, spontaneous lattice strain, and polarization until the critical size corresponding to transition to the cubic phase and disappearance of ferroelectricity is reached. In contrast, the behavior of nanocrystalline BaTiO3 ceramics with a grain...

Dense nanocrystalline BaTiO3 (BT) ceramics with grain sizes (GSs) below 100 nm obtained by spark plasma sintering (SPS), were investigated by micro-Raman spectroscopy in order to obtain information about the changes in the local order induced by size effects. The obtained spectra in the range 80–700 K showed the presence of all the crystalline phas...

Using femtosecond laser pulses (150fs duration at λ=400nm) for ablation experiments on glass samples with and without enclosed silver nanoparticles, characteristic sub-micrometer surface topologies are observed on the flat bottom of the ablation craters produced. The structures show increasing order towards periodic ripple-like features with an inc...

In the race to downsize integrated devices nanostructure fabrication is a primary challenge. Semiconductors and insulators technology has always relied on the top–down approach. Alternative "unconventional" approaches are now emerging, in particular the bottom-up approach. We describe recent work on the fabrication, patterning and integration of tw...

We achieved parallel nanoscale patterning of ferroelectric complex oxides by pulsed laser deposition through a nanostencil (i.e., through a pattern of apertures in a thin free-standing membrane). Ordered arrays of nanostructured barium titanate (BaTiO3) were obtained onto different substrates in a single deposition step, at room temperature, replic...

We report here the successful fabrication of BiFeO3 (BFO) isolated micron-sized structures by pulsed laser deposition. The islands have a relatively constant aspect ratio (height/lateral size) of 0.1-0.3. We present their local ferroelectric characterization, using piezoresponse force microscopy (PFM), showing that the micron-sized BFO islands exhi...

Dense BaTiO3 ceramics with 50 nm average grain size obtained by spark plasma sintering were investigated. The dielectric data show a broad ferro–para phase transition with a maximum permittivity of at 390 K and 1 kHz. The local ferroelectric switching behaviour was investigated by piezoresponse force microscopy. Typical piezoelectric hysteresis lo...

Epitaxial lead zirconate titanate nanoislands were obtained by a self-patterning method using the instability of ultrathin films during high-temperature treatments. After high-temperature annealing, the as-deposited film breaks into islands with a narrow size distribution. Nanostructures, as small as 20 nm lateral size with a height of 9 nm, were e...