Louis-philippe Carignan - Academia.edu (original) (raw)
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Papers by Louis-philippe Carignan
Diamond and Related Materials, 2007
Arrays of freestanding bamboo-type carbon nanofibers were grown on the surface of a porous alumin... more Arrays of freestanding bamboo-type carbon nanofibers were grown on the surface of a porous alumina substrate by laser-assisted catalytic chemical vapor deposition. A continuous wave argon ion laser operated at a wavelength of 488 nm was used to thermally decompose pure ethylene over nickel catalysts. Two different catalyst preparation methods were used and are compared with respect to the synthesis of aligned nanofibers. First, a thin nickel film (50 nm) was evaporated on the substrate and was subsequently laser annealed into nanoparticles. This preparation produced non-aligned nanofiber films. Second, a 50 nm thick catalyst layer was electrochemically deposited within the pores of an alumina substrate. This preparation produced an array of vertically aligned nanofibers. A growth rate dependence on radial position within the irradiated area was observed. Average linear growth rates ranging from 554 nm/s to 25 μm/s are reported. The nanofibers were examined by scanning electron microscopy and Raman spectroscopy. Fiber texture and nanotexture were determined by lattice fringe analysis from high resolution transmission electron microscopy images. The alignment mechanism is also discussed.
Journal of Applied Physics, 2014
ABSTRACT We have used electron holography to investigate the local magnetic behavior of isolated ... more ABSTRACT We have used electron holography to investigate the local magnetic behavior of isolated ferromagnetic nanowires (NWs) in their remanent states. The NWs consisted of periodic magnetic layers of soft, high-saturation magnetization CoFeB alloys, and non-magnetic layers of Cu. All NWs were fabricated by pulsed-potential electrodeposition in nanoporous alumina membranes. The NW composition and layer thicknesses were measured using scanning transmission electron microscopy and energy dispersive spectroscopy. The magnetization of individual NWs depended upon the thicknesses of the layers and the direction of an external magnetic field, which had been applied in situ. When the CoFeB was thicker than the diameter (50 nm), magnetization was axial for all external field directions, while thinner layers could be randomized via a perpendicular field. In some cases, magnetization inside the wire was detected at an angle with respect to the axis of the wires. In thinner Cu/CoFeB (<10 nm each) multilayer, magnetic field vortices were detected, associated with opposing magnetization in neighbouring layers. The measured crystallinity, compositions, and layer thicknesses of individual NWs were found to be significantly different from those predicted from calibration growths based on uniform composition NWs. In particular, a significant fraction of Cu (up to 50 at. %) was present in the CoFeB layers such that the measured magnetic induction was lower than expected. These results will be used to better understand previously measured effective anisotropy fields of similar NW arrays.
PHYSICAL REVIEW B, 2009
We present a model for the effective permeability tensor of nonsaturated arrays of axially magnet... more We present a model for the effective permeability tensor of nonsaturated arrays of axially magnetized bistable ferromagnetic wires based on a Maxwell-Garnett formalism generalized to include the case of two oppositely magnetized wire populations. Explicit expressions for the complex ...
Surface and Coatings Technology, 2008
Carbon nanofiber assemblies in the form of non-aligned films, arrays of vertically aligned nanofi... more Carbon nanofiber assemblies in the form of non-aligned films, arrays of vertically aligned nanofibers, aligned nanofiber mats and composite coatings were produced by laser-assisted catalytic chemical vapor deposition. A visible argon ion laser was used to thermally decompose pure ethylene over alumina supported nickel catalysts. Straight, vermicular, beaded, branched and coiled individual nanofibers were observed. The effects of the laser irradiation time on individual nanofiber characteristics, thus on overall nanofiber assembly characteristics were investigated. The arrays, nanostructured films and coatings were examined by scanning electron microscopy. The individual nanofibers were examined by transmission electron microscopy. Nanofiber texture and nanotexture were assessed by lattice fringe analysis of high resolution transmission electron microscopy images. The observed variation in the interfringe distance along the nanofiber wall suggests a pulsed growth mode. This growth mode and the nanofiber shaping mechanism are discussed. Recommendations on how to control nanofiber characteristics such as shape and internal structure are provided.
Journal of Materials Research, 2007
Epitaxial thin films of Bi 2 FeCrO 6 have been synthesized by pulsed laser deposition on SrRuO 3 ... more Epitaxial thin films of Bi 2 FeCrO 6 have been synthesized by pulsed laser deposition on SrRuO 3 on (100)-and (111)-oriented SrTiO 3 substrates. Detailed X-ray diffraction and cross-section transmission electron microscopy analysis revealed a double perovskite crystal structure of the Bi 2 FeCrO 6 epitaxial films very similar to that of BiFeO 3 along with a particularly noteworthy Fe 3+ /Cr 3+ cation ordering along the [111] direction. The films contain no detectable magnetic iron oxide impurities and have the correct cationic average stoichiometry throughout their thickness. They however exhibit a slight modulation in the Fe and Cr compositions forming complementary stripe patterns, suggesting minor local excess or depletion of Fe and Cr. The epitaxial BFCO films exhibit good ferroelectric and piezoelectric properties, in addition to magnetic properties at room temperature, as well as an unexpected crystallographic orientation dependence of their room temperature magnetic properties. Our results qualitatively confirm the predictions made using the ab-initio calculations: the double-perovskite structure of Bi 2 FeCrO 6 films exhibit a Fe 3+ /Cr 3+ cation ordering and good multiferroic properties, along with the unpredicted existence of magnetic ordering at room temperature.
Journal of Applied Physics, 2007
An effective field model based on intrawire and interwire dipolar interactions has been developed... more An effective field model based on intrawire and interwire dipolar interactions has been developed in order to describe the magnetic anisotropy in arrays of homogeneous and multilayer nanowires. Variable angle ferromagnetic resonance ͑FMR͒ and vibrating sample magnetometry ͑VSM͒ characterization techniques were used to determine the effective interaction field acting on Ni, CoFeB, and Ni/Cu nanowires. FMR spectra are well described by a rigid magnetization model and VSM data are in rough agreement with a mean longitudinal field model. FMR and VSM values of the effective fields are mutually consistent and in fair agreement with the values calculated with the model. The results show that the anisotropy of our arrays is strongly dominated by the dipolar interactions.
![Research paper thumbnail of Epitaxial thin films of the multiferroic double perovskite Bi[sub 2]FeCrO[sub 6] grown on (100)-oriented SrTiO[sub 3] substrates: Growth, characterization, and optimization](https://attachments.academia-assets.com/41162425/thumbnails/1.jpg)
](Journal of Applied Physics, 2009
The influence of the deposition pressure PO 2 and substrate temperature T S during the growth of ... more The influence of the deposition pressure PO 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 Bi2FeCrO6 thin films on SrTiO 3 substrates is possible only in a narrow deposition parameter window. We find that the pure Bi 2 FeCrO 6 phase is formed within a narrow window around an oxygen pressure PO 2 =1.2×10 −2 mbar and around a substrate temperature T S =680 °C. At lower temperature or higher pressure, Bi 7.38 Cr 0.62 O 12+x _also called (b*Bi 2 O 3 )and Bi 2 Fe4O 9 /Bi 2 (Fe,Cr) 4 O 9+x phases are detected, while at lower pressure or higher temperature a (Fe,Cr) 3 O 4 phase forms. Some of these secondary phases are not well known and have not been previously studied. We previously reported Fe/Cr cation ordering as the probable origin of the tenfold improvement in magnetization at saturation of our Bi 2 FeCrO 6 film, compared to BiFeO 3 . Here, we address the effect of the degree of cationic ordering on the magnetic properties of the Bi 2 FeCrO 6 single phase. Polarization measurements at room temperature reveal that our Bi2FeCrO6 films have excellent ferroelectric properties with ferroelectric hysteresis loops exhibiting a remanent polarization as high as 55-60 µC/cm 2 along the pseudocubic (001) direction.
![Research paper thumbnail of Growth, structure, and properties of epitaxial thin films of first-principles predicted multiferroic Bi[sub 2]FeCrO[sub 6]](https://attachments.academia-assets.com/41156971/thumbnails/1.jpg)
](Applied Physics Letters, 2006
We report the structural and physical properties of epitaxial Bi 2 FeCrO 6 thin films on epitaxia... more We report the structural and physical properties of epitaxial Bi 2 FeCrO 6 thin films on epitaxial SrRuO 3 grown on (100)-oriented SrTiO 3 substrates by pulsed laser ablation.
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
The properties of epitaxial Bi2FeCrO6 thin films, recently synthesized by pulsed laser deposition... more 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 2μB per formula unit and a polarization of ~80 μC/cm 2 at 0K). The existence of magnetic ordering at room temperature for this material is an unexpected but very promising result that needs to be further
Diamond and Related Materials, 2007
Arrays of freestanding bamboo-type carbon nanofibers were grown on the surface of a porous alumin... more Arrays of freestanding bamboo-type carbon nanofibers were grown on the surface of a porous alumina substrate by laser-assisted catalytic chemical vapor deposition. A continuous wave argon ion laser operated at a wavelength of 488 nm was used to thermally decompose pure ethylene over nickel catalysts. Two different catalyst preparation methods were used and are compared with respect to the synthesis of aligned nanofibers. First, a thin nickel film (50 nm) was evaporated on the substrate and was subsequently laser annealed into nanoparticles. This preparation produced non-aligned nanofiber films. Second, a 50 nm thick catalyst layer was electrochemically deposited within the pores of an alumina substrate. This preparation produced an array of vertically aligned nanofibers. A growth rate dependence on radial position within the irradiated area was observed. Average linear growth rates ranging from 554 nm/s to 25 μm/s are reported. The nanofibers were examined by scanning electron microscopy and Raman spectroscopy. Fiber texture and nanotexture were determined by lattice fringe analysis from high resolution transmission electron microscopy images. The alignment mechanism is also discussed.
Journal of Applied Physics, 2014
ABSTRACT We have used electron holography to investigate the local magnetic behavior of isolated ... more ABSTRACT We have used electron holography to investigate the local magnetic behavior of isolated ferromagnetic nanowires (NWs) in their remanent states. The NWs consisted of periodic magnetic layers of soft, high-saturation magnetization CoFeB alloys, and non-magnetic layers of Cu. All NWs were fabricated by pulsed-potential electrodeposition in nanoporous alumina membranes. The NW composition and layer thicknesses were measured using scanning transmission electron microscopy and energy dispersive spectroscopy. The magnetization of individual NWs depended upon the thicknesses of the layers and the direction of an external magnetic field, which had been applied in situ. When the CoFeB was thicker than the diameter (50 nm), magnetization was axial for all external field directions, while thinner layers could be randomized via a perpendicular field. In some cases, magnetization inside the wire was detected at an angle with respect to the axis of the wires. In thinner Cu/CoFeB (<10 nm each) multilayer, magnetic field vortices were detected, associated with opposing magnetization in neighbouring layers. The measured crystallinity, compositions, and layer thicknesses of individual NWs were found to be significantly different from those predicted from calibration growths based on uniform composition NWs. In particular, a significant fraction of Cu (up to 50 at. %) was present in the CoFeB layers such that the measured magnetic induction was lower than expected. These results will be used to better understand previously measured effective anisotropy fields of similar NW arrays.
PHYSICAL REVIEW B, 2009
We present a model for the effective permeability tensor of nonsaturated arrays of axially magnet... more We present a model for the effective permeability tensor of nonsaturated arrays of axially magnetized bistable ferromagnetic wires based on a Maxwell-Garnett formalism generalized to include the case of two oppositely magnetized wire populations. Explicit expressions for the complex ...
Surface and Coatings Technology, 2008
Carbon nanofiber assemblies in the form of non-aligned films, arrays of vertically aligned nanofi... more Carbon nanofiber assemblies in the form of non-aligned films, arrays of vertically aligned nanofibers, aligned nanofiber mats and composite coatings were produced by laser-assisted catalytic chemical vapor deposition. A visible argon ion laser was used to thermally decompose pure ethylene over alumina supported nickel catalysts. Straight, vermicular, beaded, branched and coiled individual nanofibers were observed. The effects of the laser irradiation time on individual nanofiber characteristics, thus on overall nanofiber assembly characteristics were investigated. The arrays, nanostructured films and coatings were examined by scanning electron microscopy. The individual nanofibers were examined by transmission electron microscopy. Nanofiber texture and nanotexture were assessed by lattice fringe analysis of high resolution transmission electron microscopy images. The observed variation in the interfringe distance along the nanofiber wall suggests a pulsed growth mode. This growth mode and the nanofiber shaping mechanism are discussed. Recommendations on how to control nanofiber characteristics such as shape and internal structure are provided.
Journal of Materials Research, 2007
Epitaxial thin films of Bi 2 FeCrO 6 have been synthesized by pulsed laser deposition on SrRuO 3 ... more Epitaxial thin films of Bi 2 FeCrO 6 have been synthesized by pulsed laser deposition on SrRuO 3 on (100)-and (111)-oriented SrTiO 3 substrates. Detailed X-ray diffraction and cross-section transmission electron microscopy analysis revealed a double perovskite crystal structure of the Bi 2 FeCrO 6 epitaxial films very similar to that of BiFeO 3 along with a particularly noteworthy Fe 3+ /Cr 3+ cation ordering along the [111] direction. The films contain no detectable magnetic iron oxide impurities and have the correct cationic average stoichiometry throughout their thickness. They however exhibit a slight modulation in the Fe and Cr compositions forming complementary stripe patterns, suggesting minor local excess or depletion of Fe and Cr. The epitaxial BFCO films exhibit good ferroelectric and piezoelectric properties, in addition to magnetic properties at room temperature, as well as an unexpected crystallographic orientation dependence of their room temperature magnetic properties. Our results qualitatively confirm the predictions made using the ab-initio calculations: the double-perovskite structure of Bi 2 FeCrO 6 films exhibit a Fe 3+ /Cr 3+ cation ordering and good multiferroic properties, along with the unpredicted existence of magnetic ordering at room temperature.
Journal of Applied Physics, 2007
An effective field model based on intrawire and interwire dipolar interactions has been developed... more An effective field model based on intrawire and interwire dipolar interactions has been developed in order to describe the magnetic anisotropy in arrays of homogeneous and multilayer nanowires. Variable angle ferromagnetic resonance ͑FMR͒ and vibrating sample magnetometry ͑VSM͒ characterization techniques were used to determine the effective interaction field acting on Ni, CoFeB, and Ni/Cu nanowires. FMR spectra are well described by a rigid magnetization model and VSM data are in rough agreement with a mean longitudinal field model. FMR and VSM values of the effective fields are mutually consistent and in fair agreement with the values calculated with the model. The results show that the anisotropy of our arrays is strongly dominated by the dipolar interactions.
Journal of Applied Physics, 2009
The influence of the deposition pressure PO 2 and substrate temperature T S during the growth of ... more The influence of the deposition pressure PO 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 Bi2FeCrO6 thin films on SrTiO 3 substrates is possible only in a narrow deposition parameter window. We find that the pure Bi 2 FeCrO 6 phase is formed within a narrow window around an oxygen pressure PO 2 =1.2×10 −2 mbar and around a substrate temperature T S =680 °C. At lower temperature or higher pressure, Bi 7.38 Cr 0.62 O 12+x _also called (b*Bi 2 O 3 )and Bi 2 Fe4O 9 /Bi 2 (Fe,Cr) 4 O 9+x phases are detected, while at lower pressure or higher temperature a (Fe,Cr) 3 O 4 phase forms. Some of these secondary phases are not well known and have not been previously studied. We previously reported Fe/Cr cation ordering as the probable origin of the tenfold improvement in magnetization at saturation of our Bi 2 FeCrO 6 film, compared to BiFeO 3 . Here, we address the effect of the degree of cationic ordering on the magnetic properties of the Bi 2 FeCrO 6 single phase. Polarization measurements at room temperature reveal that our Bi2FeCrO6 films have excellent ferroelectric properties with ferroelectric hysteresis loops exhibiting a remanent polarization as high as 55-60 µC/cm 2 along the pseudocubic (001) direction.
Applied Physics Letters, 2006
We report the structural and physical properties of epitaxial Bi 2 FeCrO 6 thin films on epitaxia... more We report the structural and physical properties of epitaxial Bi 2 FeCrO 6 thin films on epitaxial SrRuO 3 grown on (100)-oriented SrTiO 3 substrates by pulsed laser ablation.
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
The properties of epitaxial Bi2FeCrO6 thin films, recently synthesized by pulsed laser deposition... more 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 2μB per formula unit and a polarization of ~80 μC/cm 2 at 0K). The existence of magnetic ordering at room temperature for this material is an unexpected but very promising result that needs to be further