Paul McCloskey | Tyndall National Institute (original) (raw)
Papers by Paul McCloskey
2019 22nd European Microelectronics and Packaging Conference & Exhibition (EMPC), 2019
Miniaturization of efficient integrated voltage regulators is critical in order to fully benefit ... more Miniaturization of efficient integrated voltage regulators is critical in order to fully benefit from dynamic voltage and frequency scaling. A major challenge to this is the high parasitic loss of inductor cores at switching frequencies in the MHz range. In this study, we report on a novel soft magnetic core material with anisotropic magnetic properties. This composite core is fabricated using magnetic field directed assembly of magnetic particles in an epoxy matrix. Various experimental conditions were explored, and subsequent image analytics of the resulting samples was used to optimize the process parameters, in order to yield the desired morphology. Magnetic measurements revealed improved magnetization, lower coercivity and higher permeability along the percolation axis of the magnetic particles when compared to isotropic composites with the same particle loading. In addition, the permeability of the anisotropic composites remained close to constant up to 100 MHz. Finally, a funicular “necking” structure with nano-sizedparticles assembled around contactpoints of micro-sizedparticles in the composite was achieved via a bi-modal particle distribution, resulting in further improvements in magnetic properties. Our anisotropic composite core materials are attractive candidates to establish highly efftcient power inductors.
Journal of Magnetism and Magnetic Materials, 2021
Abstract Soft magnetic thin films with in-plane uniaxial magnetic anisotropy are of significant i... more Abstract Soft magnetic thin films with in-plane uniaxial magnetic anisotropy are of significant importance for a broad range of technological applications, including high-frequency power conversion. In-plane uniaxial anisotropy in amorphous films is of particular interest for ultra-low materials loss and MHz frequency operations. The present work is focused on one of the fundamental mechanisms, i.e., residual stress, that can negate the uniaxial anisotropy in amorphous films by engendering perpendicular magnetisation and hence, undermining the soft magnetic performance. It is quantified how the nature of residual stress, compressive or tensile, transforms the magnetisation from an in-plane to an out-of-plane configuration, also well-known as spin-reorientation transition (SRT). A correlation between engineered residual stress in multilayer stacks, induced by the uneven expansion of metallic/dielectric layers following a thermal-shock scheme, and SRT mechanism demonstrates tensile stress inside the films undermines the soft magnetic performance. We suggest the magnetic softness can be retained by eluding sources of tensile stress during fabrication or post-processing of the amorphous films.
Improved Resistivity (ρ) and Anisotropy field (Hk) could result in CoP performance greater than s... more Improved Resistivity (ρ) and Anisotropy field (Hk) could result in CoP performance greater than sputttered CoTaZr, with improved performance at high frequency and an increased deposition rate Acknowledgements: Intel Corporation Enterprise Ireland Tyndall National Institute References i D.S. Gardner, G. Schrom, P. Hazucha, et al. “Integrated on-chip inductors using magnetic material”, J. Appl. Phys. 103, 07E927-1 (2008) ii Satish Prabhakaran et al., IEEE Trans. On Magnetics., 39, 3190 (2003) iii D.S. Gardner, G. Schrom, P. Hazucha, et al. “Integrated on-chip inductors using magnetic material”, J. Appl. Phys. 103, 07E927-1 (2008) iv W.P. Jayasekara, J.A. Mabin, M.H. Kryder, IEEE T. Mag., 34(4), 1438 (1998) High-frequency complex permeability curves for selected magnetic materials and fit to theoretical model -200 0 200 400 600 80
2021 IEEE Applied Power Electronics Conference and Exposition (APEC), 2021
The integration of a high frequency (2-20 MHz) inductor device into the Printed Circuit Board (PC... more The integration of a high frequency (2-20 MHz) inductor device into the Printed Circuit Board (PCB) of a power converter would enable higher density integration of power converters [1] [2]. High frequency magnetic materials are required to reduce the size of an inductor device. This paper will consider commercially available thin flexible planar magnetic materials with a thickness of less than 500 µm. These materials are shown capable of withstanding laser cutting into toroidal shapes. These magnetic cores are then used to create toroidal inductors which are electrically characterised in order to calculate the magnetic material properties. The standard performance factor [3] of the materials is used to make a comparison across frequencies. An embedded in-PCB toroidal inductor is fabricated with the thin flexible planar magnetic material. Finally, a thermal simulation of the embedded in-PCB inductor is shown and the power loss density limitations of the device are discussed.
Journal of Alloys and Compounds, 2021
Abstract A thermodynamics-based approach, Calculation of Phase Diagram (CALPHAD), combined with t... more Abstract A thermodynamics-based approach, Calculation of Phase Diagram (CALPHAD), combined with topological instability parameters are proposed and experimentally evaluated, in order to optimise in-situ nanocrystallisation of rapidly quenched CoFeB alloys and exploit their remarkable Bs = 1.57 T. The high Ms of the alloy is attributed to the precipitation of the metastable Co7Fe3 nanocrystalline phase dispersed heterogeneously in the amorphous matrix. High Ms of Co7Fe3 phase can also be inferred from the high hyperfine magnetic field interactions of the Fe nuclei calculated from Mossbauer spectra. It is worth noting that the in-situ nanocrystallisation is a volume phenomenon, instead of surface crystallisation at the air-side of ribbons owning to lower cooling rates. We judge, based on nucleation theory, that the formation of the metastable phase is kinetically favoured, when compared to the equilibrium phases, hence promoting the high Ms, when compared with conventional Co-rich amorphous alloys. The local atomic order of nanocrystllised phase was confirmed by X-ray and electron diffraction techniques. Using Mossbauer spectroscopy and the extracted distribution of the hyperfine magnetic field, it is asserted that cobalt atoms form clusters, as they attract each other to form ordered structures, and boron atoms undergo only short-range ordering, likely due to covalent bond formation, governed by the size and electronegativity differences with the atoms in the amorphous matrix. We suggest the proposed CALPHAD-assisted design of nanostructured alloys, along with an in-situ nanocrystallisation, provides a practical scheme to develop novel functional alloys with the best possible balance of coercivity and saturation, exclusively designed for a high tech application.
Microsystems & Nanoengineering, 2021
As demand accelerates for multifunctional devices with a small footprint and minimal power consum... more As demand accelerates for multifunctional devices with a small footprint and minimal power consumption, 2.5D and 3D advanced packaging architectures have emerged as an essential solution that use through-substrate vias (TSVs) as vertical interconnects. Vertical stacking enables chip packages with increased functionality, enhanced design versatility, minimal power loss, reduced footprint and high bandwidth. Unlocking the potential of photolithography for vertical interconnect access (VIA) fabrication requires fast and accurate predictive modeling of diffraction effects and resist film photochemistry. This procedure is especially challenging for broad-spectrum exposure systems that use, for example, Hg bulbs with g-, h-, and i-line UV radiation. In this paper, we present new methods and equations for VIA latent image determination in photolithography that are suitable for broad-spectrum exposure and negate the need for complex and time-consuming in situ metrology. Our technique is acc...
Journal of Magnetism and Magnetic Materials, 2020
32nd European Mask and Lithography Conference, 2016
In recent years, increased demand for high aspect ratio MEMS structures has driven the need for t... more In recent years, increased demand for high aspect ratio MEMS structures has driven the need for thick photoresist fabrication processes. In this work, the optimization of a thick photoresist process using a negative tone resist (THB-151N) is described. A thickness of 85 μm is obtained with an aspect ratio of 17:1 in a single coating process, with a 5 μm pitch. Conventional UV lithography is used and its parameters are optimized in order to achieve straight and near vertical sidewall profiles. The developed patterns are used as a mold to electroplate high aspect ratio copper windings of micro-inductors and micro-transformers. A high aspect ratio yields a copper track with a large cross sectional area resulting in a lower DC resistance. This enables a further reduction in the footprint area allowing for a more efficient manufacturing process and smaller device size. Unlike other high aspect ratio resist such as SU-8, this resist does not need a post exposure bake and can be readily removed after metal electroplating.
32nd European Mask and Lithography Conference, 2016
Epoxy-based resist SU-8 is widely used in the development and fabrication of high-aspect-ratio (H... more Epoxy-based resist SU-8 is widely used in the development and fabrication of high-aspect-ratio (HAR) MEMS structures. It has proven to be a suitable photoresist combining thick layer coating and good adhesion on silicon substrates as well as possessing good mechanical and chemical stability. However, the trend towards minia- turization and increasing packaging density has pushed the demand for challenging micro-machining processes. As an example, a novel design of a MEMS microinductor requires a dielectric permanent layer coated in deep silicon trenches in order to insulate copper windings from the magnetic material deposited in these trenches. This requires the development of a photolithography process which enables the coating of a void-free layer filling the trenches. In this paper, the use of thick SU-8 photoresist for filling deep silicon trenches is investigated. Different SU-8 formulations are analyzed, processed and results are compared. As a result, an optimized process is developed to achieve void-free filled trenches and a uniform planar layer above them, with near vertical sidewall patterns.
Microelectronics Reliability, 2001
This paper describes the design, fabrication and test of a range of third order LC low pass Butte... more This paper describes the design, fabrication and test of a range of third order LC low pass Butterworth filters in MCM-L technology. There are seven filters in the range, each consisting of two inductors and one capacitor with cut-off frequencies ranging from 10 to 540 MHz. Inductance values range from 9.9 to 530 nH, and capacitance values vary from 14
This paper presents an investigation into the use of high aspect ratio conductors to improve the ... more This paper presents an investigation into the use of high aspect ratio conductors to improve the performance of RF inductors. Also presented is a review of commercially available technologies for RF chip inductors. The objective is to provide an analysis of the inductor parameters against which the high aspect ratio coils can be compared. A range of inductors from 10nH to 100nH in varying footprint areas is designed for fabrication using a novel rapid prototyping technique. High frequency (1GHz) 2-D and 3-D finite element modelling is used to provide an understanding of the behaviour of the high aspect ratio coils. Results from this analysis predict improvement of 15-30% in Q-factors compared planar equivalents.
Sensors and Actuators A: Physical, 2009
Sensors and Actuators A: Physical, 2006
Journal of Magnetism and Magnetic Materials, 2004
Journal of Magnetism and Magnetic Materials, 2008
Electroplating is compatible with the deposition of relatively thick layers i.e. several μm to 10... more Electroplating is compatible with the deposition of relatively thick layers i.e. several μm to 10s- of μm. However eddy current losses mean that thick layers will have an inferior frequency response. We have used a low content phosphorous bath together with pulse reverse plating to generate Co-rich and Co-deficient multi-nanolayers of CoP having improved saturation magnetisation and a better frequency
Journal of Magnetism and Magnetic Materials, 2007
Journal of Magnetism and Magnetic Materials, 2008
We have investigated CoNiFe and CoNiFe–C electrodeposited by pulse reverse plating (PRP) and dire... more We have investigated CoNiFe and CoNiFe–C electrodeposited by pulse reverse plating (PRP) and direct current (DC) techniques. CoNiFe(PRP) films with composition Co59.4Fe27.7Ni12.8 show coercivity of 95Am−1 (1.2Oe) and magnetization saturation flux (μ0Ms) of 1.8T. Resistivity of CoNiFe (PRP) is about 24μΩcm and permeability remains almost constant μr′ ∼475 up to 30MHz with a quality factor (Q) larger than 10. Additionally, the permeability spectra analysis shows that CoNiFe exhibits a classical eddy current loss at zero bias field and ferromagnetic resonance (FMR) when biased with 0.05T. Furthermore, a crossover between eddy current and FMR loss is observed for CoNiFe-PRP when baised with 0.05T. DC and PRP plated CoNiFe–C, which have resistivity and permeability of 85, 38μΩcm, μr′=165 and 35 with Q>10 up to 320MHz, respectively, showed only ferromagnetic resonance losses. The ferromagnetic resonance peaks in CoNiFe and CoNiFe–C are broad and resembles a Gaussian distribution of FMR frequencies. The incorporation of C to CoNiFe reduces eddy current loss, but also reduces the FMR frequency.
Journal of Magnetism and Magnetic Materials, 2005
Power inductors have been fabricated on silicon substrates using low-temperature IC compatible pr... more Power inductors have been fabricated on silicon substrates using low-temperature IC compatible processes. The electrical properties of these micro-inductors have been measured and discussed. A maximum quality factor of 6 at 4MHz has been achieved with an inductance value of about 160nH. The DC saturation currents of the non-gapped and gapped inductors are ∼500 and 700mA, respectively. The relatively high Q factor and the load current characteristics allow these micro-machined inductors to be used in integrated power converters.
Journal of Electronic Materials, 2004
IEEE Transactions on Power Electronics, 2003
2019 22nd European Microelectronics and Packaging Conference & Exhibition (EMPC), 2019
Miniaturization of efficient integrated voltage regulators is critical in order to fully benefit ... more Miniaturization of efficient integrated voltage regulators is critical in order to fully benefit from dynamic voltage and frequency scaling. A major challenge to this is the high parasitic loss of inductor cores at switching frequencies in the MHz range. In this study, we report on a novel soft magnetic core material with anisotropic magnetic properties. This composite core is fabricated using magnetic field directed assembly of magnetic particles in an epoxy matrix. Various experimental conditions were explored, and subsequent image analytics of the resulting samples was used to optimize the process parameters, in order to yield the desired morphology. Magnetic measurements revealed improved magnetization, lower coercivity and higher permeability along the percolation axis of the magnetic particles when compared to isotropic composites with the same particle loading. In addition, the permeability of the anisotropic composites remained close to constant up to 100 MHz. Finally, a funicular “necking” structure with nano-sizedparticles assembled around contactpoints of micro-sizedparticles in the composite was achieved via a bi-modal particle distribution, resulting in further improvements in magnetic properties. Our anisotropic composite core materials are attractive candidates to establish highly efftcient power inductors.
Journal of Magnetism and Magnetic Materials, 2021
Abstract Soft magnetic thin films with in-plane uniaxial magnetic anisotropy are of significant i... more Abstract Soft magnetic thin films with in-plane uniaxial magnetic anisotropy are of significant importance for a broad range of technological applications, including high-frequency power conversion. In-plane uniaxial anisotropy in amorphous films is of particular interest for ultra-low materials loss and MHz frequency operations. The present work is focused on one of the fundamental mechanisms, i.e., residual stress, that can negate the uniaxial anisotropy in amorphous films by engendering perpendicular magnetisation and hence, undermining the soft magnetic performance. It is quantified how the nature of residual stress, compressive or tensile, transforms the magnetisation from an in-plane to an out-of-plane configuration, also well-known as spin-reorientation transition (SRT). A correlation between engineered residual stress in multilayer stacks, induced by the uneven expansion of metallic/dielectric layers following a thermal-shock scheme, and SRT mechanism demonstrates tensile stress inside the films undermines the soft magnetic performance. We suggest the magnetic softness can be retained by eluding sources of tensile stress during fabrication or post-processing of the amorphous films.
Improved Resistivity (ρ) and Anisotropy field (Hk) could result in CoP performance greater than s... more Improved Resistivity (ρ) and Anisotropy field (Hk) could result in CoP performance greater than sputttered CoTaZr, with improved performance at high frequency and an increased deposition rate Acknowledgements: Intel Corporation Enterprise Ireland Tyndall National Institute References i D.S. Gardner, G. Schrom, P. Hazucha, et al. “Integrated on-chip inductors using magnetic material”, J. Appl. Phys. 103, 07E927-1 (2008) ii Satish Prabhakaran et al., IEEE Trans. On Magnetics., 39, 3190 (2003) iii D.S. Gardner, G. Schrom, P. Hazucha, et al. “Integrated on-chip inductors using magnetic material”, J. Appl. Phys. 103, 07E927-1 (2008) iv W.P. Jayasekara, J.A. Mabin, M.H. Kryder, IEEE T. Mag., 34(4), 1438 (1998) High-frequency complex permeability curves for selected magnetic materials and fit to theoretical model -200 0 200 400 600 80
2021 IEEE Applied Power Electronics Conference and Exposition (APEC), 2021
The integration of a high frequency (2-20 MHz) inductor device into the Printed Circuit Board (PC... more The integration of a high frequency (2-20 MHz) inductor device into the Printed Circuit Board (PCB) of a power converter would enable higher density integration of power converters [1] [2]. High frequency magnetic materials are required to reduce the size of an inductor device. This paper will consider commercially available thin flexible planar magnetic materials with a thickness of less than 500 µm. These materials are shown capable of withstanding laser cutting into toroidal shapes. These magnetic cores are then used to create toroidal inductors which are electrically characterised in order to calculate the magnetic material properties. The standard performance factor [3] of the materials is used to make a comparison across frequencies. An embedded in-PCB toroidal inductor is fabricated with the thin flexible planar magnetic material. Finally, a thermal simulation of the embedded in-PCB inductor is shown and the power loss density limitations of the device are discussed.
Journal of Alloys and Compounds, 2021
Abstract A thermodynamics-based approach, Calculation of Phase Diagram (CALPHAD), combined with t... more Abstract A thermodynamics-based approach, Calculation of Phase Diagram (CALPHAD), combined with topological instability parameters are proposed and experimentally evaluated, in order to optimise in-situ nanocrystallisation of rapidly quenched CoFeB alloys and exploit their remarkable Bs = 1.57 T. The high Ms of the alloy is attributed to the precipitation of the metastable Co7Fe3 nanocrystalline phase dispersed heterogeneously in the amorphous matrix. High Ms of Co7Fe3 phase can also be inferred from the high hyperfine magnetic field interactions of the Fe nuclei calculated from Mossbauer spectra. It is worth noting that the in-situ nanocrystallisation is a volume phenomenon, instead of surface crystallisation at the air-side of ribbons owning to lower cooling rates. We judge, based on nucleation theory, that the formation of the metastable phase is kinetically favoured, when compared to the equilibrium phases, hence promoting the high Ms, when compared with conventional Co-rich amorphous alloys. The local atomic order of nanocrystllised phase was confirmed by X-ray and electron diffraction techniques. Using Mossbauer spectroscopy and the extracted distribution of the hyperfine magnetic field, it is asserted that cobalt atoms form clusters, as they attract each other to form ordered structures, and boron atoms undergo only short-range ordering, likely due to covalent bond formation, governed by the size and electronegativity differences with the atoms in the amorphous matrix. We suggest the proposed CALPHAD-assisted design of nanostructured alloys, along with an in-situ nanocrystallisation, provides a practical scheme to develop novel functional alloys with the best possible balance of coercivity and saturation, exclusively designed for a high tech application.
Microsystems & Nanoengineering, 2021
As demand accelerates for multifunctional devices with a small footprint and minimal power consum... more As demand accelerates for multifunctional devices with a small footprint and minimal power consumption, 2.5D and 3D advanced packaging architectures have emerged as an essential solution that use through-substrate vias (TSVs) as vertical interconnects. Vertical stacking enables chip packages with increased functionality, enhanced design versatility, minimal power loss, reduced footprint and high bandwidth. Unlocking the potential of photolithography for vertical interconnect access (VIA) fabrication requires fast and accurate predictive modeling of diffraction effects and resist film photochemistry. This procedure is especially challenging for broad-spectrum exposure systems that use, for example, Hg bulbs with g-, h-, and i-line UV radiation. In this paper, we present new methods and equations for VIA latent image determination in photolithography that are suitable for broad-spectrum exposure and negate the need for complex and time-consuming in situ metrology. Our technique is acc...
Journal of Magnetism and Magnetic Materials, 2020
32nd European Mask and Lithography Conference, 2016
In recent years, increased demand for high aspect ratio MEMS structures has driven the need for t... more In recent years, increased demand for high aspect ratio MEMS structures has driven the need for thick photoresist fabrication processes. In this work, the optimization of a thick photoresist process using a negative tone resist (THB-151N) is described. A thickness of 85 μm is obtained with an aspect ratio of 17:1 in a single coating process, with a 5 μm pitch. Conventional UV lithography is used and its parameters are optimized in order to achieve straight and near vertical sidewall profiles. The developed patterns are used as a mold to electroplate high aspect ratio copper windings of micro-inductors and micro-transformers. A high aspect ratio yields a copper track with a large cross sectional area resulting in a lower DC resistance. This enables a further reduction in the footprint area allowing for a more efficient manufacturing process and smaller device size. Unlike other high aspect ratio resist such as SU-8, this resist does not need a post exposure bake and can be readily removed after metal electroplating.
32nd European Mask and Lithography Conference, 2016
Epoxy-based resist SU-8 is widely used in the development and fabrication of high-aspect-ratio (H... more Epoxy-based resist SU-8 is widely used in the development and fabrication of high-aspect-ratio (HAR) MEMS structures. It has proven to be a suitable photoresist combining thick layer coating and good adhesion on silicon substrates as well as possessing good mechanical and chemical stability. However, the trend towards minia- turization and increasing packaging density has pushed the demand for challenging micro-machining processes. As an example, a novel design of a MEMS microinductor requires a dielectric permanent layer coated in deep silicon trenches in order to insulate copper windings from the magnetic material deposited in these trenches. This requires the development of a photolithography process which enables the coating of a void-free layer filling the trenches. In this paper, the use of thick SU-8 photoresist for filling deep silicon trenches is investigated. Different SU-8 formulations are analyzed, processed and results are compared. As a result, an optimized process is developed to achieve void-free filled trenches and a uniform planar layer above them, with near vertical sidewall patterns.
Microelectronics Reliability, 2001
This paper describes the design, fabrication and test of a range of third order LC low pass Butte... more This paper describes the design, fabrication and test of a range of third order LC low pass Butterworth filters in MCM-L technology. There are seven filters in the range, each consisting of two inductors and one capacitor with cut-off frequencies ranging from 10 to 540 MHz. Inductance values range from 9.9 to 530 nH, and capacitance values vary from 14
This paper presents an investigation into the use of high aspect ratio conductors to improve the ... more This paper presents an investigation into the use of high aspect ratio conductors to improve the performance of RF inductors. Also presented is a review of commercially available technologies for RF chip inductors. The objective is to provide an analysis of the inductor parameters against which the high aspect ratio coils can be compared. A range of inductors from 10nH to 100nH in varying footprint areas is designed for fabrication using a novel rapid prototyping technique. High frequency (1GHz) 2-D and 3-D finite element modelling is used to provide an understanding of the behaviour of the high aspect ratio coils. Results from this analysis predict improvement of 15-30% in Q-factors compared planar equivalents.
Sensors and Actuators A: Physical, 2009
Sensors and Actuators A: Physical, 2006
Journal of Magnetism and Magnetic Materials, 2004
Journal of Magnetism and Magnetic Materials, 2008
Electroplating is compatible with the deposition of relatively thick layers i.e. several μm to 10... more Electroplating is compatible with the deposition of relatively thick layers i.e. several μm to 10s- of μm. However eddy current losses mean that thick layers will have an inferior frequency response. We have used a low content phosphorous bath together with pulse reverse plating to generate Co-rich and Co-deficient multi-nanolayers of CoP having improved saturation magnetisation and a better frequency
Journal of Magnetism and Magnetic Materials, 2007
Journal of Magnetism and Magnetic Materials, 2008
We have investigated CoNiFe and CoNiFe–C electrodeposited by pulse reverse plating (PRP) and dire... more We have investigated CoNiFe and CoNiFe–C electrodeposited by pulse reverse plating (PRP) and direct current (DC) techniques. CoNiFe(PRP) films with composition Co59.4Fe27.7Ni12.8 show coercivity of 95Am−1 (1.2Oe) and magnetization saturation flux (μ0Ms) of 1.8T. Resistivity of CoNiFe (PRP) is about 24μΩcm and permeability remains almost constant μr′ ∼475 up to 30MHz with a quality factor (Q) larger than 10. Additionally, the permeability spectra analysis shows that CoNiFe exhibits a classical eddy current loss at zero bias field and ferromagnetic resonance (FMR) when biased with 0.05T. Furthermore, a crossover between eddy current and FMR loss is observed for CoNiFe-PRP when baised with 0.05T. DC and PRP plated CoNiFe–C, which have resistivity and permeability of 85, 38μΩcm, μr′=165 and 35 with Q>10 up to 320MHz, respectively, showed only ferromagnetic resonance losses. The ferromagnetic resonance peaks in CoNiFe and CoNiFe–C are broad and resembles a Gaussian distribution of FMR frequencies. The incorporation of C to CoNiFe reduces eddy current loss, but also reduces the FMR frequency.
Journal of Magnetism and Magnetic Materials, 2005
Power inductors have been fabricated on silicon substrates using low-temperature IC compatible pr... more Power inductors have been fabricated on silicon substrates using low-temperature IC compatible processes. The electrical properties of these micro-inductors have been measured and discussed. A maximum quality factor of 6 at 4MHz has been achieved with an inductance value of about 160nH. The DC saturation currents of the non-gapped and gapped inductors are ∼500 and 700mA, respectively. The relatively high Q factor and the load current characteristics allow these micro-machined inductors to be used in integrated power converters.
Journal of Electronic Materials, 2004
IEEE Transactions on Power Electronics, 2003