Carpick, Robert W
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Publication Imaging and manipulation of nanometer-size liquid droplets by scanning polarization force microscopy(1996-03-01) Hu, Jun; Carpick, Robert W; Salmeron, Miquel; Xiao, Xu-dongUsing atomic force microscopy in noncontact mode, we have imaged nanometer-size liquid droplets of KOH water solutions on the surfaces of highly oriented pyrolitic graphite and mica. On graphite the droplets prefer to be adsorbed on atomic step edges. Droplets on the same step tend to be evenly spaced and of similar size. The droplets can be manipulated by the atomic force microscopy tip allowing the controllable formation of droplet patterns on the surface.Publication Incorporating Concepts of Nanotechnology into the Materials Science and Engineering Classroom and Laboratory(2003-01-01) Bentley, Anne K; Crone, Wendy C; Ellis, Arthur B; Payne, Amy C; Lux, Kenneth W; Carpick, Robert W; Stone, Donald; Lisensky, George C; Condren, S. MichaelThe National Science Foundation-supported Materials Research Science and Engineering Center (MRSEC) on Nanostructured Materials and Interfaces at the University of Wisconsin – Madison has an extensive and highly successful education and outreach effort. One theme of this effort is the development of instructional materials based on cutting-edge research in nanoscale science and engineering. Nanotechnology examples, such as light emitting diodes (LEDs), shape memory alloys, amorphous metals, and ferrofluids, illustrate interdisciplinary research that provides connections among materials science, chemistry, physics, and engineering. They also highlight the tools of nanotechnology, such as scanning probe microscopy, electron microscopy, self-assembly, x-ray diffraction, and chemical vapor deposition, associated with the preparation and characterization of nanostructured materials. These and other nanotechnology concepts are illustrated with video demonstrations in a web-based resource called the "Nanoworld Cineplex," which contains movies of experiments and demonstrations that can be brought into the classroom. Numerous experiments are also available in the "Nanotechnology Lab Manual," which can be used as either a virtual laboratory or as a web-based video lab manual. These resources for using nanotechnology to teach fundamental materials science and engineering principles are available at .Publication Phase imaging and the lever-sample tilt angle in dynamic atomic force microscopy(2004-11-15) D'Amato, Matthew J; Marcus, Matthew S; Eriksson, Mark A; Carpick, Robert WThe phase shift in amplitude-controlled dynamic atomic force microscopy (AFM) is shown to depend on the cantilever-sample tilt angle. For a silicon sample and tip the phase shift changes by nearly 15º for a change in tilt angle of 15º. This contribution to the phase results from the oscillating tip's motion parallel to the surface, which contributes to the overall energy dissipation. It occurs even when the measurements are carried out in the attractive regime. An off-axis dynamic AFM model incorporating van der Waals attraction and a thin viscous damping layer near the surface successfully describes the observed phase shifts. This effect must be considered to interpret phase images quantitatively. © 2004 American Institute of Physics.Publication Negative stiffness and enhanced damping of individual multiwalled carbon nanotubes(2008-01-24) Yap, H W; Lakes, R S; Carpick, Robert WThe mechanical instabilities and viscoelastic response of individual multiwalled carbon nanotubes and nanofibers (MWCNTs/Fs) under uniaxial compression are studied with atomic force microscopy. Specific buckling events are evident by regimes of negative stiffness, i.e., marked drops in force with increasing compression. Uniaxial cyclic loading can be repeatedly executed even in initially postbuckled regimes, where the CNTs/Fs display incremental negative stiffness. Increases in mechanical damping of 145–600 % in these initially postbuckled regimes, as compared to the linear prebuckled regimes, are observed. Increased damping is attributed to frictional energy dissipation of walls in buckled configurations of the MWCNTs/Fs. This represents the extension of the concept of negative stiffness to the scale of nanostructures and opens up possibilities for designing nanocomposites with high stiffness and high damping simultaneously.Publication Angle-Resolved Environmental X-Ray Photoelectron Spectroscopy: A New Laboratory Setup for Photoemission Studies at Pressures up to 0.4 Torr(2012-09-27) Wabiszewski, Graham E; Mangolini, F.; Adiga, Vivek P; Åhlund, J.; Egberts, P.; Streller, F.; Backlund, K.; Carpick, Robert W; Karlsson, P. G; Wannberg, B.The paper presents the development and demonstrates the capabilities of a new laboratory-based environmental X-ray photoelectron spectroscopy system incorporating an electrostatic lens and able to acquire spectra up to 0.4 Torr. The incorporation of a two-dimensional detector provides imaging capabilities and allows the acquisition of angle-resolved data in parallel mode over an angular range of 14° without tilting the sample. The sensitivity and energy resolution of the spectrometer have been investigated by analyzing a standard Ag foil both under high vacuum (10−8 Torr) conditions and at elevated pressures of N2 (0.4 Torr). The possibility of acquiring angle-resolved data at different pressures has been demonstrated by analyzing a silicon/silicon dioxide (Si/SiO2) sample. The collected angle-resolved spectra could be effectively used for the determination of the thickness of the native silicon oxide layer.Publication Friction and Molecular Deformation in the Tensile Regime(1999-02-01) Burns, A. R; Carpick, Robert W; Michalske, T. ARecent molecular level studies of energy dissipation in sliding friction have suggested a contribution from adhesive forces. In order to observe this directly, we have constructed a scanning force microscope with decoupled lateral and normal force sensors to simultaneously observe the onset of both friction and attractive forces. Measurements made on self-assembling alkanethiol films with chemically different tail groups show that friction can increase with stronger adhesive intermolecular forces and from the associated tensile deformation and collective motion of the thiol chains.Publication Thermal Stability and Rehybridization of Carbon Bonding in Tetrahedral Amorphous Carbon(2010-02-11) Grierson, David S; Konicek, Andrew; Sumant, A V; Friedmann, T A; Carpick, Robert W; Sullivan, J PWe preform a quantitative investigation of the energetics of thermally induced sp3 → sp2 conversion of carbon-carbon bonds in tetrahedral amorphous carbon (ta-C) films by using near edge x-ray absorption fine structure (NEXAFS) and Raman spectroscopy. We investigate the evolution of the bonding configuration in ta-C thin films subjected to high temperature annealing in flowing Argon gas using a rapid thermal annealing furnace over the range of 200-1000 ºC. We observe no substantial change in bonding structure below 600 ºC, and by 1000 ºC a significant increase in the sp2 bonding in the film is observed. No oxygen bonding is detected in the NEXAFS spectra, but we do observe an isosbestic point, demonstrating that the thermally driven sp3 → sp2 conversion reaction occurs without passing through an intermediate transition state. This allows us to use NEAFS spectra of thermally annealed ta-C films to quantitatively determine that the activation energy for directly converting the sp3-bonded carbon to the spPublication Small Amplitude Reciprocating Wear Performance of Diamond-like Carbon Films: Dependence of Film Composition and Counterface Material(2007-07-01) Bares, Jason A; Sumant, Anirudha V; Grierson, David S; Carpick, Robert W; Sridharan, KumarSmall amplitude (50 μm) reciprocating wear of hydrogen-containing diamond-like carbon (DLC) films of different compositions has been examined against silicon nitride and polymethyl-methacrylate (PMMA) counter-surfaces, and compared with the performance of an uncoated steel substrate. Three films were studied: a DLC film of conventional composition, a fluorine-containing DLC film (F-DLC), and silicon-containing DLC film. The films were deposited on steel substrates from plasmas of organic precursor gases using the Plasma Immersion Ion Implantation and Deposition (PIIID) process, which allows for the non-line-of-sight deposition of films with tailored compositions. The amplitude of the resistive frictional force during the reciprocating wear experiments was monitored in situ, and the magnitude of film damage due to wear was evaluated using optical microscopy, optical profilometry, and atomic force microscopy. Wear debris was analyzed using scanning electron microscopy and energy dispersive spectroscopy. In terms of friction, the DLC and silicon-containing DLC films performed exceptionally well, showing friction coefficients less than 0.1 for both PMMA and silicon nitride counter-surfaces. DLC and silicon-containing DLC films also showed significant reductions in transfer of PMMA compared with the uncoated steel. The softer F-DLC film performed similarly well against PMMA, but against silicon nitride, friction displayed nearly periodic variations indicative of cyclic adhesion and release of worn film material during the wear process. The results demonstrate that the PIIID films achieve the well-known advantageous performance of other DLC films, and furthermore that the film performance can be significantly affected by the addition of dopants. In addition to the well-established reduction of friction and wear that DLC films generally provide, we show here that another property, low adhesiveness with PMMA, is another significant benefit in the use of DLC films.Publication Who Wants to be an Engineer? - Or Better Teaching Through Game Shows(2002-01-01) Carpick, Robert WA 50 (or 60 or 70) -minute lecture is inherently incompatible with the typical attention spans of students. The author has developed a teaching technique that successfully re-captures attention in the classroom. The technique, loosely based on a popular prime-time game show, consists of quizzing a student "on the spot" while allowing a "life-line" of polling the audience for help. The game is enjoyable for students and professor alike, but also allows review, clarification, and reinforcement of concepts. The technique is effective while only requiring minimal preparation and lecture time to be implemented.Publication Vibrations of the "beetle" scanning probe microscope: Identification of a new mode, generalized analysis, and characterization methodology(2006-03-31) Brukman, Matthew J; Carpick, Robert WThe prediction and understanding of structural resonances are required to optimize scanning probe microscope (SPM) design. Here, Euler beam theory is applied to the beetle-style SPM to derive analytic functions for the natural frequencies of three significant modes of vibration as a general function of the microscope shape, materials, and dimensions. In the first mode, the three piezoelectric legs vibrate transversely and the scanhead moves from side to side. In the second, the legs bend circumferentially and the scanhead rotates about its center. These modes have been identified previously, but here the mechanics analysis is presented in an improved form where the inertia of the piezo legs is considered, constraints on the shape of the central supporting disk are lifted, and appropriate boundary conditions are defined and enforced. In addition, we discuss a third mode that has not been previously identified. In this lowest frequency mode, two legs pivot about the stationary third leg. The predictions are tested against experimental data obtained from an atomic force microscope (AFM) built in our laboratory. We show that the mode frequencies can be determined easily using in situ motion of the AFM cantilever itself. Predicted frequencies are in good agreement with experimental results, although unpredicted modes are also observed. The simple closed-form solutions allow the designer to make quantitative comparisons when choosing the materials and dimensions used in the SPM design. Two new design criteria emerge from the analysis for optimizing the resonant response of the "beetle" scanhead: (1) the wall thickness tau of the piezo legs should be minimized, with their mean diameters increasing as tau(-1) and (2) the distance between the legs and the center of the scanhead should be adjusted to optimize the rotation mode eigenfrequency. (c) 2006 American Institute of Physics.