Carpick, Robert W
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Publication Measurement of interfacial shear (friction) with an ultrahigh vacuum atomic force microscope(1996-03-01) Carpick, Robert W; Agraït, N.; Ogletree, D. F; Salmeron, MiguelWe have studied the variation of frictional force with externally applied load for a Pt-coated atomic force microscope tip in contact with the surface of mica cleaved in ultrahigh vacuum. At low loads, the frictional force varies with load in almost exact proportion to the area of contact as predicted by the Johnson-Kendall-Roberts (JKR) theory [K. L. Johnson, K. Kendall, and A. D. Roberts, Proc. R. Sec. London Ser. A 324, 301 (1971)] of elastic adhesive contacts. The friction-load relation for a deliberately modified tip shape was proportional to an extended JKR model that predicts the area-load relation for nonparabolic tips, The tip shape was determined experimentally with a tip imaging technique and was consistent with the predicted friction behavior. This demonstrates that the frictional force is proportional to the area of contact between the tip and sample. Using the JKR/extended JKR model, interfacial surface energies and shear strengths can be estimated.Publication A Course in Micro- and Nanoscale Mechanics(2003-01-01) Carpick, Robert WAt small scales, mechanics enters a new regime where the role of surfaces, interfaces, defects, material property variations, and quantum effects play more dominant roles. A new course in nanoscale mechanics for engineering students was recently taught at the University of Wisconsin - Madison. This course provided an introduction to nanoscale engineering with a direct focus on the critical role that mechanics needs to play in this developing area. The limits of continuum mechanics were presented as well as newly developed mechanics theories and experiments tailored to study and describe micro- and nano-scale phenomena. Numerous demonstrations and experiments were used throughout the course, including synthesis and fabrication techniques for creating nanostructured materials, bubble raft models to demonstrate size scale effects in thin film structures, and a laboratory project to construct a nanofilter device. A primary focus of this paper is the laboratory content of this course, which includes an integrated series of laboratory modules utilizing atomic force microscopy, self-assembled monolayer deposition, and microfluidic technology.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 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 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 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 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 Predictions and Observations of Multiple Slip Modes in Atomic-Scale Friction(2006-09-27) Medyanik, Sergey N.; Kam Liu, Wing; Sung, In-Ha; Carpick, Robert WUsing the quasistatic Tomlinson model as a simple representation of an atomic force microscope, conditions for transitions in atomic-scale friction behavior from smooth sliding to single slips and then multiple slip regimes are derived based on energy minimization. The calculations predict and give a general explanation for transitions between different stick-slip regimes in the limit of low damping. The predictions are consistent with experimental observations of these transitions.Publication Laser heating of a sintered oxide superconductor(1991-08-15) Shi, Y. H; Lee, M.J. G; Moskovits, M.; Hsu, A.; Carpick, Robert WRaman spectroscopy, in which a laser beam serves the dual role of exciting the Raman spectrum and annealing the sample, shows promise as a means of investigating oxygen effects in the oxide superconductors. A technique is described, based on measurements of the ratios of the areas of corresponding peaks in the anti-Stokes and Stokes spectra, whereby the temperature of the illuminated region of the sample can be determined as a function of the power in the incident laser beam. It is found that, for sintered samples of bismuth 2122, a small correction must be made for the departure from thermodynamic equilibrium induced by the pumping effect of the laser beam.Publication Piezoelectric aluminum nitride nanoelectromechanical actuators(2009-08-03) Sinha, Nipun; Wabiszewski, Graham E; Carpick, Robert W; Mahameed, Rashed; piazza, Gianluca; Felmetsger, Valery V; Tanner, Shawn MThis letter reports the implementation of ultrathin (100 nm) aluminum nitride (AlN) piezoelectric layers for the fabrication of vertically deflecting nanoactuators. The films exhibit an average piezoelectric coefficient (d31~−1.9 pC/N), which is comparable to its microscale counterpart. This allows vertical deflections as large as 40 nm from 18 µm long and 350 nm thick multilayer cantilever bimorph beams with 2 V actuation. Furthermore, in-plane stress and stress gradients have been simultaneously controlled. The films exhibit leakage currents lower than 2 nA/cm2 at 1 V, and have an average relative dielectric constant of approximately 9.2 (as in thicker films). These material characteristics and actuation results make the AlN nanofilms ideal candidates for the realization of nanoelectromechanical switches for low power logic applications.