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Richard Gaal

Cette personne a quitté l’EPFL

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Publications associées (49)

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Enhanced low-temperature thermoelectrical properties of BiTeCl grown by topotactic method

Helmuth Berger, László Forró, Arnaud Magrez, Richard Gaal, Philippe Bugnon, Ana Akrap, Jacim Jacimovic, Sergiy Katrych, Andrea Pisoni, Xavier François Mettan

We developed a topotactic strategy to grow BiTeCl single crystals. Structural characterization by means of X-ray diffraction was performed, and the high crystallinity of the material was proven. Measurements of the thermoelectrical coefficients electrical ...

Pergamon-Elsevier Science Ltd2014

Pressure dependence of the large-polaron transport in anatase TiO2 single crystals

Radomir Zikic, László Forró, Helmuth Berger, Arnaud Magrez, Richard Gaal, Jacim Jacimovic, George Cristian Vaju

We have measured the pressure and temperature dependences of the resistivity and the thermoelectric power of anatase, TiO2. The resistivity varies with T-3 at high temperatures, and its absolute value is in the 1 Omega cm range. Below 60 K, the resistivity ...

IOP Publishing - EPL Association2012

Carbon nanotubes-SU8 composite for flexible conductive inkjet printable applications

Jürgen Brugger, László Forró, Arnaud Magrez, Richard Gaal, Kristopher Pataky, Marijana Mionic Ebersold

We have developed a conducting composite based on multi-walled carbon nanotubes and bisphenol A novolak epoxy resin (SU8) for inkjet printing purposes. We could deposit regular conducting stripes and arrays of 150 mu m spots on glass and on flexible polyet ...

Royal Society of Chemistry2012

Continuous-wave far-infrared ESR spectrometer for high-pressure measurements

László Forró, Andrzej Sienkiewicz, Bálint Náfrádi, Richard Gaal

We present a newly-developed microwave probe for performing sensitive high-field/multi-frequency electron spin resonance (ESR) measurements under high hydrostatic pressures. The system consists of a BeCu-made pressure-resistant vessel, which accommodates t ...

Academic Press Inc - Elsevier Science2008

High-pressure study of anatase TiO2

László Forró, Helmuth Berger, Arnaud Magrez, Richard Gaal, Jacim Jacimovic, George Cristian Vaju

We report resistivity and thermo-electric power measurements of the anatase phase of TiO2 under pressure up to 2.3 GPa. Despite its transparent appearance, the single crystal of anatase exhibits a metallic-like resistivity above 60 K, at all pressures. The ...

2010

Pr4Fe2As2Te1-xO4: A layered FeAs-based superconductor

László Forró, Richard Gaal, Sergiy Katrych, Andrea Pisoni

We report crystal growth at high pressure, structure determination, and magnetic and transport studies of an oxypnictide superconductor Pr4Fe2As2Te1-xO4. Its structure resembles the known 1111 phase except for the considerably larger c lattice constant and ...

Amer Physical Soc2013

Ultrasensitive 1D field-effect phototransistors: CH3NH3PbI3 nanowire sensitized individual carbon nanotubes

László Forró, Bálint Náfrádi, Endre Horvath, Richard Gaal, Massimo Spina

Field-effect phototransistors were fabricated based on individual carbon nanotubes (CNTs) sensitized by CH3NH3PbI3 nanowires (MAPbI(3)NWs). These devices represent light responsivities of R = 7.7 x 10(5) A W-1 under low-lighting conditions in the nW mm(-2) ...

2016

Pressure dependence of superconducting properties of layered BaNi2P2

Henrik Moodysson Rønnow, Ivica Zivkovic, Richard Gaal, Youngro Lee

The discovery of unconventional superconductivity in a broad class of iron-based materials invoked extensive research on the corresponding compounds of other transition metals. For instance, BaNi2P2 exhibits a superconducting transition with a critical tem ...

Elsevier2023

Bullet pressure-cell design for neutron scattering experiments with horizontal magnetic fields and dilution temperatures

Henrik Moodysson Rønnow, Richard Gaal, Ellen Fogh, Gaétan Charles Antoine Giriat, Luc Testa, Jana Pásztorová

The simultaneous application of high magnetic fields and high pressures for controlling magnetic ground states is important for testing our understanding of many-body quantum theory. However, the implementation for neutron scattering experiments presents a ...

2025

High-pressure infrared spectroscopy: Tuning of the low-energy excitations in correlated electron systems

László Forró, Helmuth Berger, Richard Gaal, Balazs Sipos

We have extended the range of the high-pressure optical spectroscopy to the far-infrared region keeping the accuracy of ambient-pressure experiments. The developed method offers a powerful tool for the study of pressure-induced phase transitions and electr ...

2007

Microwave frequency modulation in continuous-wave far-infrared ESR utilizing a quasi-optical reflection bridge

László Forró, Bálint Náfrádi, Richard Gaal

We report the development of the frequency-modulation (FM) method for measuring electron spin resonance (ESR) absorption in the 210- to 420 GHz frequency range. We demonstrate that using a high-frequency ESR spectrometer without resonating microwave compon ...

Academic Press Inc - Elsevier Science2008

Tuning the length dispersion of multi-walled carbon nanotubes by ball milling

László Forró, Arnaud Magrez, Claudio Grimaldi, Richard Gaal, Marijana Mionic Ebersold, Rita Smajda, Primoz Rebernik Ribic

The statistical analysis of the length distribution of catalytic chemical vapour deposition synthesized multi-walled carbon nanotubes cut by planetary ball milling is reported. The nanotube lengths follow a log-normal distribution in a broad range of grind ...

Amer Inst Physics2013

Low temperature resistivity, thermoelectricity, and power factor of Nb doped anatase TiO2

László Forró, Arnaud Magrez, Richard Gaal, Jacim Jacimovic

The resistivity of a very high quality anatase TiO2 doped with 6% of Nb was measured from 300K down to 40 mK. No sign of superconductivity was detected. Instead, a minute quantity of cation vacancies resulted in a Kondo scattering. Measurements of thermo-e ...

Amer Inst Physics2013

Nanowires of Methylammonium Lead Iodide (CH(3)NH(3)Pbl(3)) Prepared by Low Temperature Solution-Mediated Crystallization

László Forró, Endre Horvath, Richard Gaal, Massimo Spina

We report the synthesis of Methylammonium Lead Iodide (CH3NH3PbI3) nanowires by a low temperature solution processed crystallization using a simple slip-coating method. The anisotropic particle shape exhibits advantages over nanoparticles in terms of charg ...

Amer Chemical Soc2014

Ultra-Low Thermal Conductivity in Organic-Inorganic Hybrid Perovskite CH3NH3PbI3

László Forró, Endre Horvath, Richard Gaal, Massimo Spina, Jacim Jacimovic, Andrea Pisoni

We report on the temperature dependence of thermal conductivity of single crystalline and polycrystalline organometallic perovskite CH3NH3PbI3. The comparable absolute values and temperature dependence of the two samples' morphologies indicate the minor ro ...

Amer Chemical Soc2014

Cyan titania nanowires: Spectroscopic study of the origin of the self-doping enhanced photocatalytic activity

László Forró, Arnaud Magrez, Bálint Náfrádi, Endre Horvath, Richard Gaal, Alla Arakcheeva, Massimo Spina, Jacim Jacimovic, Péter Szirmai, Laurent Syavoch Bernard

We report a detailed spectroscopic study of Ti3+ self-doped TiO2 nanowires prepared by high temperature annealing of the protonated titanate nanowires (TiONW) in hydrogen atmosphere. Hydrogenation causes a color change from white to cyan and a major increa ...

Elsevier2017

Synthesis, electrical resistivity, thermo-electric power and magnetization of cubic ZnMnO3

László Forró, Arnaud Magrez, Andrzej Sienkiewicz, Richard Gaal, Zlatko Mickovic, Jacim Jacimovic, Rita Smajda, George Cristian Vaju

Cubic ZnMnO3 powder in the form of well-crystalline nanoflakes have been synthesized at low temperatures from a nitrate precursor. The electrical properties of cubic ZuMnO(3) samples have been established by DC resistivity (rho) and thermo-electric power ( ...

Elsevier2011

L4Fe2As2Te1-xO4-yFy (L = Pr, Sm, Gd): A layered oxypnictide superconductor with T-c up to 45 K

László Forró, Richard Gaal, Sergiy Katrych, Andrea Pisoni

The synthesis and structural and physical properties of iron lanthanide oxypnictide superconductors, L4Fe2As2Te1-xO4 (L = Pr, Sm, Gd), with transition temperature at similar to 25 K are reported. Single crystals have been grown at high pressure using the c ...

Amer Physical Soc2014

Microengineered CH3NH3PbI3 Nanowire/Graphene Phototransistor for Low-Intensity Light Detection at Room Temperature

László Forró, Arnaud Magrez, Bálint Náfrádi, Endre Horvath, Richard Gaal, Massimo Spina, Mario Joe Lehmann, Laurent Syavoch Bernard

The first hybrid phototransistors are reported where the performance of a network of photoactive CH3NH3PbI3 nanowires is enhanced by CVD-grown monolayer graphene. These devices show responsivities as high as ≈2.6 × 106 A W- ...

2015

Effect of salt on the H-bond symmetrization in ice

Philippe Gillet, Richard Gaal, Livia Eleonora Bove Kado

The richness of the phase diagram of water reduces drastically at very high pressures where only two molecular phases, proton-disordered ice VII and proton-ordered ice VIII, are known. Both phases transform to the centered hydrogen bond atomic phase ice X ...

National Academy of Sciences2015