C. Friesen

Arizona State University, Phoenix, Arizona, United States

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Publications (18)68.93 Total impact

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    ABSTRACT: The under-potential deposition (UPD) & absorption of hydrogen in thin film palladium (45-75 nm) was investigated electrochemically utilizing both EQCM and thin film stress measurement techniques. The total frequency change during H absorption (desorption) as measured by EQCM is attributed to both an increase (decrease) in mass, Delta f(m), as well as the associated thin film stress evolution, Delta f(s). In order to deconvolute these two contributions, the changes in the Pd{111} thin-film stresses were measured directly by a high-resolution cantilever curvature-based stress monitoring technique. Mass incorporation and stress generation due to hydrogen absorption were recorded during cyclic voltammetric scans of increasingly cathodic potentials as well as during chronoamperometric holds in the hydrogen UPD region. The combination of stress measurements and mass uptake of hydrogen in the purely elastic regime provided a measure of a biaxially constrained partial molar volume of hydrogen in the Pd thin films, (V) over bar (biax)(II-Pd) = 0.44 cm(3)/mol. Additionally, the occurrence of hysteresis and dramatic changes in slope of stress vs. H concentration during loading and unloading of thin films is explained in the context of elastic-plastic transitions that occur in the film.
    Journal of The Electrochemical Society 01/2012; 159(5):A613. DOI:10.1149/2.069205jes · 2.86 Impact Factor
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    ABSTRACT: Room temperature ionic liquids have attracted a great deal of interest in recent years due to their remarkable physicochemical properties including high thermal stability, wide electrochemical window, and low vapor pressure. A subclass of ionic liquids, protic ionic liquids (PILs), are formed by proton transfer from a Brønsted acid to a Brønsted base, and are good candidates as electrolytes in several applications, including fuel cells, because they integrate high ionicity and proton exchange kinetics with low vapor pressure. Here we present hydrogen redox results for a number of hydrogen-saturated PILs. Specifically we study the systems diethylmethylammonium bistrifluoromethanesulfonimide, diethylmethylammonium chloroaluminate, triethylammonium triflate, diethylmethylammonium triflate, dimethylethylammonium triflate, ethylammonium nitrate, pyridinium acetate, triethylammonium methane sulfonate, diethylmethylammonium methane sulfonate, and α-picolinium triflate. We observe a significant potential gap between the potential at which proton reduction occurs and the potential at which facile hydrogen oxidation occurs (with the gap ranging from ca. 0 to 800 mV). We show that this observation correlates with differences in the energetics for proton extraction from the anion (acid with the form HA) and from the cation (acid with the form BH+), which is defined by the differences in proton free energy between the Brønsted couples HA/H− and BH+/B. This energy gap and the associated equivalence point in the titration curve fix the proton activity in these systems and determine the electrochemical potential needed to activate a proton when no lower energy sites are available in the vicinity of the electrode.
    The Journal of Physical Chemistry C 07/2009; 113(28). DOI:10.1021/jp902762c · 4.84 Impact Factor
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    ABSTRACT: This article presents an experimental procedure to perform highly localized compression tests on nanoscale structures/features, such as nanospheres and nanopillars, via standard nanoindentation equipment. Current manufacturing capabilities, such as focused ion beam (FIB), lend themselves well to the creation of micron-spaced nanostructures, but it is fundamental to target an individual instance with little or no damage to the surrounding ones. The procedure successfully addresses the problem of locating and testing purposely designed nanostructures of order of 50 nm or less. The technique is illustrated for the case of closely spaced arrays of nanopillars, which were successfully manufactured, characterized, and tested through several pieces of equipment. For the purposes of compression, along with a traditional Berkovich tip, a new multifunctional (MF) tip was devised. This last tip is endowed with a complex contact geometry enabling both atomic force microscope (AFM) scanning and flat punch compression of the nanostructure. The levels of accuracy in tip positioning as well as robustness to alignment errors are unprecedented in comparison with previous in situ compression tests. As a consequence, the MF tip becomes a versatile tool that can be used beyond uniform compression. As an example, ancillary shear tests in controlled conditions are reported. Such results may lay the bases for metal-forming processes at the nanoscale, such as nanoforging or cutting operations, which are relevant to MEMS design and manufacturing.
    02/2009; 24(03):768 - 775. DOI:10.1557/jmr.2009.0099
  • L. Mickelson, C. Friesen
    Electrochemical and Solid-State Letters 01/2009; 12(12):F43. DOI:10.1149/1.3243915 · 2.15 Impact Factor
  • L. Mickelson, Th. Heaton, C. Friesen
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    ABSTRACT: The adsorbate-induced surface stress was studied for the system CO/Pt{111}-textured thin films in CO-saturated 0.1 M HClO4 and characterized through the techniques of cyclic voltammetry and chronoamperometry. A compressive stress of −1.1 N/m was measured for a saturation coverage. It is shown that CO blocks the electrode both electrochemically (charge transfer) and physically (surface stress changes). Additionally, it is demonstrated with surface stress measurements that CO does not desorb with the removal of CO from the electrolyte. The adsorption kinetics of CO are shown to be slow, with a saturation coverage taking more than 65 s to acquire. When driven electrochemically, CO oxidation kinetics are fast, occurring in much less than 1 s.
    The Journal of Physical Chemistry C 01/2008; 112(4). DOI:10.1021/jp076502h · 4.84 Impact Factor
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    ABSTRACT: The compressive plastic strength of nanometer-scale single-crystal metallic pillars is larger than that found in conventionally sized samples. This behavior is generally associated with a change in the length scale that determines plastic behavior and the consequent inability of nanoscale samples to store dislocations. Here, we show in the case of nanocrystalline nickel pillars, for which there is a fixed microstructural length scale set by the grain size, that smaller is still stronger and find that this behavior derives from statistical expec-tations that have long been used to understand the size-dependent strength of brittle solids such as glass.
    Acta Materialia 01/2008; 56(3). DOI:10.1016/j.actamat.2007.09.044 · 3.94 Impact Factor
  • Th. Heaton, C. Friesen
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    ABSTRACT: Large changes in stress (of order GPa) are observed with relatively modest variations in applied potential (on the order of 500 mV), even in nonspecifically adsorbing electrolyte solutions. Here we present the electrocapillarity behavior (in situ surface stress evolution) of Pt{111} and Au{111} electrodes. We relate the magnitude and anodic/cathodic hysteresis of the stress−potential behavior to the potential dependent water orientation at the electrode/electrolyte interface. We show that our results are strongly correlated to previously published infrared spectroscopy data on the potential dependence of interphase structure. Finally, measurements of Pt in oxygen saturated electrolytes are presented, allowing for a direct comparison between features in the surface stress behavior and the “turn-on” potential for oxygen reduction. We found that oxygen reduction occurs only once the potential was cathodic enough to begin depleting the interface of oxygen-down oriented water.
    The Journal of Physical Chemistry C 09/2007; 111(39). DOI:10.1021/jp071109x · 4.84 Impact Factor
  • J. K. Kennedy, C. Friesen
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    ABSTRACT: Thin film stress evolution during physical vapor deposition is highly sensitive to the exact nature of the growth environment. It has been previously observed that during the growth of Cu films, stress evolution is acutely affected by oxygen partial pressure. However, changes in partial pressure imply a number of changes to the growth environment and to the condition of the growth surface. To specifically examine the role of adsorption on growth stresses, in this work we have grown Cu Volmer-Weber films, adsorbed a known quantity of oxygen, and continued growth once ultrahigh vacuum conditions were again achieved. This enabled the study of stress evolution as a function of adsorbate coverage, independent of background pressure. We found that even at low coverages, adsorbed oxygen has a profound impact on stress evolution. Additionally, we found that the adsorbed oxygen is consumed by the growing film over a significant thickness of growth and we have extracted the rate of oxygen consumption. We also observed an epitaxial stress associated with the continued growth of Cu on the underlying strained O-dosed Cu film, and show that the reversible stress is apparently unaffected by the oxygen adsorption step.
    Journal of Applied Physics 03/2007; 101(5):054904-054904-4. DOI:10.1063/1.2436838 · 2.19 Impact Factor
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    ABSTRACT: Significant effects of sample dimension on the yield strength of metallic crystals have been known for more than 50 years when researchers identified this phenomenon in metallic whiskers. These sample-size effects are once again attracting great interest with the discovery of the indentation size effect and the enhanced yield strength found for sub-micrometer diameter focused ion beam (FIB)-machined metallic pillars. Here, we discuss these issues and suggest mechanisms that may be responsible for the observed behaviors. In the case of FIB-machined pillars we draw an analogy between the yield strength of these structures and the fracture strength of glass rods and suggest that the experimentally observed yield behavior in these pillars is consistent with that expected from extreme value statistics. Additionally, we revisit the topic of surface effects in crystal plasticity and suggest a new mechanism via which a free surface could act as a measurable source of hardening for a crystal that has a bulk interior free of defects such as dislocations or grain boundaries. Finally we suggest experimental approaches that can be used to test the ideas discussed herein.
    Acta Materialia 10/2006; 54(17-54):4533-4538. DOI:10.1016/j.actamat.2006.05.041 · 3.94 Impact Factor
  • C. Friesen
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    ABSTRACT: Surface and interface excess quantities are coupled or ill-defined for ultra-thin films. Yet, surface and interface energy are consistently used to describe monolayer-range heteroepitaxial structures. Here, we examine the convergence of interfacial thermodynamic quantities to the well-defined thermodynamic (separability) limit in the systems Ag/Au(111) and Al/Au(111). Convergence to separability occurs together with the interface-induced electronic structure and interlayer spacing perturbations. We discuss how lack of thermodynamic separability affects growth mode, coherency, and domain organization.
    Surface Science 03/2006; 600(5):1012-1016. DOI:10.1016/j.susc.2005.12.034 · 1.87 Impact Factor
  • Cody Friesen, Carl V Thompson
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    ABSTRACT: A Comment on the Letter by R. Koch, Dongzhi Hu, and A. K. Das, Phys. Rev. Lett. 94, 146101 (2005)PRLTAO0031-900710.1103/PhysRevLett.94.146101. The authors of the Letter offer a Reply.
    Physical Review Letters 12/2005; 95(22):229601; author reply 229602. DOI:10.1103/PhysRevLett.95.229601 · 7.73 Impact Factor
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    ABSTRACT: Experimental results are presented for stress evolution, in vacuum and electrolyte, for the first monolayer of Cu on Au(111). In electrolyte the monolayer is pseudomorphic and the stress-thickness change is -0.60 N/m, while conventional epitaxy theory predicts a value of +7.76 N/m. In vacuum, the monolayer is incoherent with the underlying gold. Using a combination of first-principles based calculations and molecular dynamic simulations we analyzed these results and demonstrate that in electrolyte, overlayer coherency is maintained owing to anion adsorption.
    Physical Review Letters 11/2005; 95(16):166106. DOI:10.1103/PhysRevLett.95.166106 · 7.73 Impact Factor
  • C Friesen, C V Thompson
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    ABSTRACT: Stress evolution during intermittent homoepitaxial growth of (111)-oriented Cu and Ag thin films has been studied. A tensile stress change is observed when growth is stopped, but the change is reversed when growth is resumed. Reflection high energy electron diffraction analysis of the atomic scale surface roughness during intermittent growth demonstrates a strong correlation between the surface structure and reversible stress evolution. The results are discussed in terms of an evolving surface defect population.
    Physical Review Letters 08/2004; 93(5):056104. DOI:10.1103/PhysRevLett.93.056104 · 7.73 Impact Factor
  • Cody Friesen, Carl V. Thompson
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    ABSTRACT: Stress evolution during the intermittent growth of Volmer-Weber Cu thin films and homoepitaxial growth of (111)-oriented Cu and Ag thin films has been studied. In all systems a tensile stress change is observed when growth is stopped, but the change is reversed when growth is resumed. In addition to direct experimental evidence, thermodynamic and kinetic arguments are employed to show that the reversible stress phenomenology is due to the entire ensemble of surface defects evolving during the growth process. In the earliest stages of growth a direct correlation is made between the stress evolution and an increase in the adatom population. At longer timescales, when a more complex set of defects are expected, reflection high energy electron diffraction analysis of the atomic scale surface roughness is used to explain the stress evolution phenomenology. These observations are correlated to stress evolution in nanometer scale thin film islands to demonstrate the importance of surface defect densities on stress in nanostructures.
  • C. Friesen, S. C. Seel, C. V. Thompson
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    ABSTRACT: Stresses caused by Volmer–Weber growth of polycrystalline Cu films have been measured in situ during: Island nucleation and growth, island coalescence, and post-coalescence film thickening. Growth interruptions followed by resumption of growth resulted in the observation of reversible stress changes in all regimes. Reversible stress changes in the pre-coalescence and post-coalescence regimes are similar in that: The stress evolves in the tensile direction during growth interruptions, the initial rate of stress evolution is significantly faster when growth is resumed than when growth is first interrupted, and the magnitude of the reversible stress change increases with increasing pre-interruption deposition rate. It is argued that reversible stress changes are associated with changes in adatom and other surface defect concentrations, corresponding with changes in the growth flux. It is shown that the change in stress-thickness product with changing film thickness (the instantaneous stress) can be related to the adatom–surface interaction energy. High sensitivity stress measurements were made at a rate of 1000 measurements per second, and the instantaneous stress at the initiation of growth was measured at all stages of growth. The initial instantaneous stress and the adatom–surface interaction energy increased in the pre-coalescence regime and reached a fixed, maximum value once coalescence had occurred. The measured interaction energy in the post-coalescence regime is 0.67±0.1 eV, which corresponds well with values calculated using molecular dynamics. © 2004 American Institute of Physics.
    Journal of Applied Physics 01/2004; 95(3):1011-1020. DOI:10.1063/1.1637728 · 2.19 Impact Factor
  • C Friesen, C V Thompson
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    ABSTRACT: From in situ stress measurements, we have observed that a large component of the precoalescence compressive stress that develops during Volmer-Weber growth of polycrystalline Cu films relaxes reversibly. This phenomenon is similar to the reversible stress relaxation previously observed in the postcoalescence regime. We have also observed that less than a tenth of a monolayer of deposition leads to an instantaneous stress of order 1 GPa. The stress changes in both the precoalescence and postcoalescence regimes of growth are explained by changes in the adatom population during and after deposition.
    Physical Review Letters 10/2002; 89(12):126103. DOI:10.1103/PhysRevLett.89.126103 · 7.73 Impact Factor
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    ABSTRACT: There are two fundamental excess thermodynamic parameters that characterize a surface, the surface free energy and the surface stress. The surface free energy is the reversible work per unit area to form new surface while maintaining a constant equilibrium density of surface atoms. The surface stress is the reversible work per unit area required to form new surface by elastic deformation of a preexisting surface, and thus the atom density is altered. For a fluid surface the surface free energy is equal to the surface stress, but for a solid this is in general not true. We develop thermodynamic arguments that describe proper interpretations of wafer curvature experiments that are typically used in electrocapillarity experiments of solid electrodes. Additionally, we consider stress evolution during underpotential deposition. The sources of stress relate to electrocapillarity differences between overlayer and substrate, interface stress, and coherency stress. Experimental results are presented for the systems Pb2+/Au(111), Pb2+/ Ag(111), and Ag+/Au(111). We show how it is possible to use the experimental data to extract results for the interface stresses in each of these systems. The following values of interface stress were determined:  for the incommensurate Pb/Au(111) interface, 1.76 ± 0.04 N/m; for the incommensurate Pb/Ag(111) interface, 0.9 ± 0.04 N/m; and for the coherent Ag/Au(111) interface, −0.08 ± 0.04 N/m. Finally, we employ the thermodynamic arguments developed to consider two important problems in the electrocapillarity of solids. The first is a comparison of the magnitude of the change in surface free energy and surface stress that result from pure double − layer effects. The second is the potential-induced 23 × √3 (111) reconstruction that occurs on Au surfaces. Here, we calculate the difference in surface stress between the reconstructed and unreconstructed surface, obtaining −0.43 N/m, which compares favorably with recently published experimental results.
    Langmuir 01/2001; 17(3). DOI:10.1021/la000911m · 4.38 Impact Factor
  • C. Friesen

Publication Stats

356 Citations
68.93 Total Impact Points

Institutions

  • 2005–2012
    • Arizona State University
      • Department of Mechanical Engineering
      Phoenix, Arizona, United States
  • 2009
    • Università degli Studi di Roma "Tor Vergata"
      • Dipartimento di Scinze e Tecnologie Chimiche
      Roma, Latium, Italy
  • 2002–2004
    • Massachusetts Institute of Technology
      • Department of Materials Science and Engineering
      Cambridge, Massachusetts, United States
  • 2001
    • Johns Hopkins University
      Baltimore, Maryland, United States