Megan Cordill - Academia.edu (original) (raw)

Papers by Megan Cordill

Surface and Coatings Technology

In today's semiconductor industry materials and deposition techniques have to fulfill the sop... more In today's semiconductor industry materials and deposition techniques have to fulfill the sophisticated product requirements of modern microelectronic devices. To meet the quality standards of the desired products thin film deposition process have to be tuned very accurately to any avoid contaminations and incorporations of chemical impurities. For that reason a wafer curvature instrument was developed enabling the characterization of the thermomechanical behavior of semiconductor materials from room temperature up to 1000°C. This allowed the investigation of the stress evolution of nitrogen and hydrogen doped undoped silicon glass (USG) SiO2, films during an annealing process which are performed at the same temperatures as industrial deposition. Based on the stress-temperature results and complementary characterization techniques of infrared spectroscopy, nanoindentation, ellipsometry, light microscopy and atomic force microscopy a qualitative model was developed to describe th...

Thin Solid Films, 2021

Abstract Sputter deposited Mo/Al/Mo multilayers are widely used material systems for electrodes i... more Abstract Sputter deposited Mo/Al/Mo multilayers are widely used material systems for electrodes in display technologies. In this study, the electro-mechanical behavior of simplified bilayer versions was improved for flexible applications through substitution of the Mo by Mo-Ta alloy layers. Sputter deposited Al/Mo-Ta bilayers were tested under uniaxial tensile and cyclic bending loads. Compared to similar Al/Mo bilayers from previous studies, the Mo-Ta interlayer with 50 at.% Ta improved the crack onset strain under tensile load by more than 1% strain. Furthermore, after 50 000 cycles under 1.3% bending strain, the Al/Mo-Ta bilayers were nearly undamaged and experienced a relatively small electrical resistance increase of 25%, compared to Al/Mo bilayers, which were 40 to 100 times higher. This work shows that the substitution of the brittle Mo interlayer with a more ductile Mo-Ta interlayer can improve the performance and lifetime of the electrodes and is more suitable for flexible displays than the currently used materials.

Although metallic glasses (MGs) exhibit a unique combination of mechanical and chemical propertie... more Although metallic glasses (MGs) exhibit a unique combination of mechanical and chemical properties, their application as structural or functional materials is hindered by the lack of ductility which leads to catastrophic brittle-like fracture. When the size of a MG sample is reduced below some critical value, typically of the order of a few hundred nanometers, then considerable ductility can be observed. However, this size effect was demonstrated so far mostly by nanomechanical testing inside a transmission electron microscope using samples prepared by focused ion beam (FIB) milling. Whether the ductile-like behavior of submicrometer-sized metallic glasses is a real “intrinsic” size effect or it is rather caused by extrinsic factors like sample shape, ion beam effect or parameters of the testing setup is currently a subject of extensive discussions in the community. In this contribution the tensile properties of thin film Pd82Si18 MGs grown by sputter deposition on a polymer substra...

Die gestiegenen Anforderungen an die Materialien zur Herstellung von flexibler Elektronik erforde... more Die gestiegenen Anforderungen an die Materialien zur Herstellung von flexibler Elektronik erfordern neue Materialsysteme mit verbesserten mechanischen Eigenschaften. In dieser Arbeit wurden zwei Designstrategien untersucht, um gezielt die Eigenschaften der Metallschicht-Systeme zu verbessern. Dabei wurde (i) die verbesserte Haftung einer leitfahigen Metallschicht (Cu) auf Polymersubstrat mit Hilfe einer haftvermittelnden Zwischenschicht (Cr) sowie (ii) eine verzogerte Rissbildung durch eine dehnungsinduzierte Phasenumwandlung von metastabilem hexagonalen Co untersucht. Das Adhasions- und Verformungsverhalten unter Zugbelastung wurde mit Rasterelektronenmikroskopie, Rasterkraftmikroskopie und Synchrotronstrahlung charakterisiert. Wahrend (i) die Verwendung einer haftvermittelnden Zwischenschicht zu Rissinitiierung und damit vorzeitigem Versagen fuhrt, ist (ii) ein sehr effizienter Mechanismus um die Rissbildung und damit das Versagen eines Schichtsystems signifikant zu verzogern.

Aidan A Taylor, Laboratory for Mechanics of Materials and Nanostructures, Empa, Thun, Switzerland... more Aidan A Taylor, Laboratory for Mechanics of Materials and Nanostructures, Empa, Thun, Switzerland Aidan.a.taylor@gmail.com Rachel L Schoeppner, Laboratory for Mechanics of Materials and Nanostructures, Empa, Thun, Switzerland Megan J Cordill, Erich Schmid Institute, Austrian Academy of Sciences, Leoben, Austria Johann Michler, Laboratory for Mechanics of Materials and Nanostructures, Empa, Thun, Switzerland Hussein M Zbib, Washington State University, Mechanical and Materials Engineering, Pullman, USA David F Bahr, Purdue University, Materials Engineering, West Lafayette, USA

Microelectronic Engineering, 2017

Alice Lassnig, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben,... more Alice Lassnig, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben, Austria alice.lassnig@oeaw.ac.at Christoph Gammer, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben, Austria Daniel Kiener, Department Materials Science, Montanuniversität Leoben, Austria Christian Mitterer, Department Materials Science, Monatnuniversität Leoben, Austria Megan J. Cordill, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben, Austria

Scientific Reports, 2021

Cellulose fibers are a major industrial input, but due to their irregular shape and anisotropic m... more Cellulose fibers are a major industrial input, but due to their irregular shape and anisotropic material response, accurate material characterization is difficult. Single fiber tensile testing is the most popular way to estimate the material properties of individual fibers. However, such tests can only be performed along the axis of the fiber and are associated with problems of enforcing restraints. Alternative indirect approaches, such as micro-mechanical modeling, can help but yield results that are not fully decoupled from the model assumptions. Here, we compare these methods with nanoindentation as a method to extract elastic material constants of the individual fibers. We show that both the longitudinal and the transverse elastic modulus can be determined, additionally enabling the measurement of fiber properties in-situ inside a sheet of paper such that the entire industrial process history is captured. The obtained longitudinal modulus is comparable to traditional methods for...

Journal of the Mechanics and Physics of Solids, 2021

Abstract In recent years, the investigation of adhesion properties of thin films on brittle subst... more Abstract In recent years, the investigation of adhesion properties of thin films on brittle substrates is receiving more attention due to the spread of thin film applications (coatings, protective layers, conductive layers in microelectronics, etc.). However, a basic approach for adhesion measurements proposed by Hutchinson and Suo almost three decades ago is still widely used due to its easy applicability. This approach uses thin film spontaneous buckling using residual compressive stresses in the film, however, it is based on Euler beam theory and accounts only for elastic behavior. Modern material combinations may lead to permanent plastic deformations, even under the controlled experimental conditions according to the elastic model. This work aims at investigating the plastic deformation influence on the experimental procedure according to Hutchinson and Suo by the means of the finite element analysis on the specific Mo-Cu-glass system. The deformations of spontaneously formed buckles are compared between purely elastic, (more realistic) elastic-plastic model and previously published experimental results together with quantification of the dissipated energy via the current finite element model. The comparison of the two numerical approaches shows non-negligible plastic deformations of the spontaneously formed buckles which has an effect on the film deformed shape (corresponding to the experimental observations) as well as on the portion of the shear loading at the delamination crack tip. This indicates that the plastic deformation during the buckling delamination may have some impact on the stability of the delamination crack.

Chemistry of Materials, 2021

Stretchable conductive films were obtained by screen printing and thermal treatment of a homogeno... more Stretchable conductive films were obtained by screen printing and thermal treatment of a homogenous ink comprising a thermally reducible silver formate complex, an acrylate monomer, and a radical i...

Journal of Vacuum Science & Technology A, 2020

A Ni81W19 target was dc sputter eroded at constant target power density from a tiltable magnetron... more A Ni81W19 target was dc sputter eroded at constant target power density from a tiltable magnetron at different Ar pressures. The combination with a stationary mass-energy analyzer allowed investigating the abundance of different species within the plasma as well as the ion energy distribution functions of 40 Ar + , 58 Ni + , and 184 W + at any given angle θ between 0°and 90°from the target normal. Ar + ions are detected at θ angles close to the target normal, whereas metal atoms are observed at larger θ angles. Ni is emitted at smaller θ angles compared to W. Both investigated metal ion energy distributions exhibit a high energy tail with energies up to 50 eV. Increasing the Ar pressure first affects the trajectories of Ni before W atoms. This can be understood by considering the smaller mass difference between Ni and Ar compared to W and Ar. This enables more effective energy transfer and larger scattering angles of Ni undergoing collisions with Ar compared to W. Subsequent film depositions on a spherical-shell substrate holder, covering angles between 0°and 80°from the target normal, allowed for a comparison of the angular dependent film-and plasma-compositions. This correlative analysis suggests that selective resputtering of Ni by energetic Ar neutrals, reflected from the target, leads to the observed difference between the target and film composition during sputter deposition from a multielement NiW target.

Surface and Coatings Technology, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Scripta Materialia, 2020

This study presents detailed microstructural investigations on single and bilayer thin films of t... more This study presents detailed microstructural investigations on single and bilayer thin films of two medium entropy alloys (MEAs) synthesized using magnetron sputter deposition. Single layer thin films of CoCrFeNi and AlCoCrFe show single-phase face-centered cubic (fcc) and body-centered (bcc) structure, respectively. The bilayer thin film consisting of CoCrFeNi (fcc) and AlCoCrFe (bcc) has a sharp interface between them with an equiatomic composition. Nanodiffraction was used to characterize planar defects in the fcc films. This first study on bilayer film of two MEAs is transformative to other systems and will help fundamental studies on high entropy alloys.

Surface and Coatings Technology

In today's semiconductor industry materials and deposition techniques have to fulfill the sop... more In today's semiconductor industry materials and deposition techniques have to fulfill the sophisticated product requirements of modern microelectronic devices. To meet the quality standards of the desired products thin film deposition process have to be tuned very accurately to any avoid contaminations and incorporations of chemical impurities. For that reason a wafer curvature instrument was developed enabling the characterization of the thermomechanical behavior of semiconductor materials from room temperature up to 1000°C. This allowed the investigation of the stress evolution of nitrogen and hydrogen doped undoped silicon glass (USG) SiO2, films during an annealing process which are performed at the same temperatures as industrial deposition. Based on the stress-temperature results and complementary characterization techniques of infrared spectroscopy, nanoindentation, ellipsometry, light microscopy and atomic force microscopy a qualitative model was developed to describe th...

Thin Solid Films, 2021

Abstract Sputter deposited Mo/Al/Mo multilayers are widely used material systems for electrodes i... more Abstract Sputter deposited Mo/Al/Mo multilayers are widely used material systems for electrodes in display technologies. In this study, the electro-mechanical behavior of simplified bilayer versions was improved for flexible applications through substitution of the Mo by Mo-Ta alloy layers. Sputter deposited Al/Mo-Ta bilayers were tested under uniaxial tensile and cyclic bending loads. Compared to similar Al/Mo bilayers from previous studies, the Mo-Ta interlayer with 50 at.% Ta improved the crack onset strain under tensile load by more than 1% strain. Furthermore, after 50 000 cycles under 1.3% bending strain, the Al/Mo-Ta bilayers were nearly undamaged and experienced a relatively small electrical resistance increase of 25%, compared to Al/Mo bilayers, which were 40 to 100 times higher. This work shows that the substitution of the brittle Mo interlayer with a more ductile Mo-Ta interlayer can improve the performance and lifetime of the electrodes and is more suitable for flexible displays than the currently used materials.

Although metallic glasses (MGs) exhibit a unique combination of mechanical and chemical propertie... more Although metallic glasses (MGs) exhibit a unique combination of mechanical and chemical properties, their application as structural or functional materials is hindered by the lack of ductility which leads to catastrophic brittle-like fracture. When the size of a MG sample is reduced below some critical value, typically of the order of a few hundred nanometers, then considerable ductility can be observed. However, this size effect was demonstrated so far mostly by nanomechanical testing inside a transmission electron microscope using samples prepared by focused ion beam (FIB) milling. Whether the ductile-like behavior of submicrometer-sized metallic glasses is a real “intrinsic” size effect or it is rather caused by extrinsic factors like sample shape, ion beam effect or parameters of the testing setup is currently a subject of extensive discussions in the community. In this contribution the tensile properties of thin film Pd82Si18 MGs grown by sputter deposition on a polymer substra...

Die gestiegenen Anforderungen an die Materialien zur Herstellung von flexibler Elektronik erforde... more Die gestiegenen Anforderungen an die Materialien zur Herstellung von flexibler Elektronik erfordern neue Materialsysteme mit verbesserten mechanischen Eigenschaften. In dieser Arbeit wurden zwei Designstrategien untersucht, um gezielt die Eigenschaften der Metallschicht-Systeme zu verbessern. Dabei wurde (i) die verbesserte Haftung einer leitfahigen Metallschicht (Cu) auf Polymersubstrat mit Hilfe einer haftvermittelnden Zwischenschicht (Cr) sowie (ii) eine verzogerte Rissbildung durch eine dehnungsinduzierte Phasenumwandlung von metastabilem hexagonalen Co untersucht. Das Adhasions- und Verformungsverhalten unter Zugbelastung wurde mit Rasterelektronenmikroskopie, Rasterkraftmikroskopie und Synchrotronstrahlung charakterisiert. Wahrend (i) die Verwendung einer haftvermittelnden Zwischenschicht zu Rissinitiierung und damit vorzeitigem Versagen fuhrt, ist (ii) ein sehr effizienter Mechanismus um die Rissbildung und damit das Versagen eines Schichtsystems signifikant zu verzogern.

Aidan A Taylor, Laboratory for Mechanics of Materials and Nanostructures, Empa, Thun, Switzerland... more Aidan A Taylor, Laboratory for Mechanics of Materials and Nanostructures, Empa, Thun, Switzerland Aidan.a.taylor@gmail.com Rachel L Schoeppner, Laboratory for Mechanics of Materials and Nanostructures, Empa, Thun, Switzerland Megan J Cordill, Erich Schmid Institute, Austrian Academy of Sciences, Leoben, Austria Johann Michler, Laboratory for Mechanics of Materials and Nanostructures, Empa, Thun, Switzerland Hussein M Zbib, Washington State University, Mechanical and Materials Engineering, Pullman, USA David F Bahr, Purdue University, Materials Engineering, West Lafayette, USA

Microelectronic Engineering, 2017

Alice Lassnig, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben,... more Alice Lassnig, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben, Austria alice.lassnig@oeaw.ac.at Christoph Gammer, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben, Austria Daniel Kiener, Department Materials Science, Montanuniversität Leoben, Austria Christian Mitterer, Department Materials Science, Monatnuniversität Leoben, Austria Megan J. Cordill, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben, Austria

Scientific Reports, 2021

Cellulose fibers are a major industrial input, but due to their irregular shape and anisotropic m... more Cellulose fibers are a major industrial input, but due to their irregular shape and anisotropic material response, accurate material characterization is difficult. Single fiber tensile testing is the most popular way to estimate the material properties of individual fibers. However, such tests can only be performed along the axis of the fiber and are associated with problems of enforcing restraints. Alternative indirect approaches, such as micro-mechanical modeling, can help but yield results that are not fully decoupled from the model assumptions. Here, we compare these methods with nanoindentation as a method to extract elastic material constants of the individual fibers. We show that both the longitudinal and the transverse elastic modulus can be determined, additionally enabling the measurement of fiber properties in-situ inside a sheet of paper such that the entire industrial process history is captured. The obtained longitudinal modulus is comparable to traditional methods for...

Journal of the Mechanics and Physics of Solids, 2021

Abstract In recent years, the investigation of adhesion properties of thin films on brittle subst... more Abstract In recent years, the investigation of adhesion properties of thin films on brittle substrates is receiving more attention due to the spread of thin film applications (coatings, protective layers, conductive layers in microelectronics, etc.). However, a basic approach for adhesion measurements proposed by Hutchinson and Suo almost three decades ago is still widely used due to its easy applicability. This approach uses thin film spontaneous buckling using residual compressive stresses in the film, however, it is based on Euler beam theory and accounts only for elastic behavior. Modern material combinations may lead to permanent plastic deformations, even under the controlled experimental conditions according to the elastic model. This work aims at investigating the plastic deformation influence on the experimental procedure according to Hutchinson and Suo by the means of the finite element analysis on the specific Mo-Cu-glass system. The deformations of spontaneously formed buckles are compared between purely elastic, (more realistic) elastic-plastic model and previously published experimental results together with quantification of the dissipated energy via the current finite element model. The comparison of the two numerical approaches shows non-negligible plastic deformations of the spontaneously formed buckles which has an effect on the film deformed shape (corresponding to the experimental observations) as well as on the portion of the shear loading at the delamination crack tip. This indicates that the plastic deformation during the buckling delamination may have some impact on the stability of the delamination crack.

Chemistry of Materials, 2021

Stretchable conductive films were obtained by screen printing and thermal treatment of a homogeno... more Stretchable conductive films were obtained by screen printing and thermal treatment of a homogenous ink comprising a thermally reducible silver formate complex, an acrylate monomer, and a radical i...

Journal of Vacuum Science & Technology A, 2020

A Ni81W19 target was dc sputter eroded at constant target power density from a tiltable magnetron... more A Ni81W19 target was dc sputter eroded at constant target power density from a tiltable magnetron at different Ar pressures. The combination with a stationary mass-energy analyzer allowed investigating the abundance of different species within the plasma as well as the ion energy distribution functions of 40 Ar + , 58 Ni + , and 184 W + at any given angle θ between 0°and 90°from the target normal. Ar + ions are detected at θ angles close to the target normal, whereas metal atoms are observed at larger θ angles. Ni is emitted at smaller θ angles compared to W. Both investigated metal ion energy distributions exhibit a high energy tail with energies up to 50 eV. Increasing the Ar pressure first affects the trajectories of Ni before W atoms. This can be understood by considering the smaller mass difference between Ni and Ar compared to W and Ar. This enables more effective energy transfer and larger scattering angles of Ni undergoing collisions with Ar compared to W. Subsequent film depositions on a spherical-shell substrate holder, covering angles between 0°and 80°from the target normal, allowed for a comparison of the angular dependent film-and plasma-compositions. This correlative analysis suggests that selective resputtering of Ni by energetic Ar neutrals, reflected from the target, leads to the observed difference between the target and film composition during sputter deposition from a multielement NiW target.

Surface and Coatings Technology, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Scripta Materialia, 2020

This study presents detailed microstructural investigations on single and bilayer thin films of t... more This study presents detailed microstructural investigations on single and bilayer thin films of two medium entropy alloys (MEAs) synthesized using magnetron sputter deposition. Single layer thin films of CoCrFeNi and AlCoCrFe show single-phase face-centered cubic (fcc) and body-centered (bcc) structure, respectively. The bilayer thin film consisting of CoCrFeNi (fcc) and AlCoCrFe (bcc) has a sharp interface between them with an equiatomic composition. Nanodiffraction was used to characterize planar defects in the fcc films. This first study on bilayer film of two MEAs is transformative to other systems and will help fundamental studies on high entropy alloys.