Browsing by Subject "Stiffness"
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Item Open Access High-resolution imaging of elastic properties using harmonic cantilevers(Elsevier, 2004) Sahin, O.; Yaralioglu, G.; Grow, R.; Zappe, S. F.; Atalar, Abdullah; Quate, C.; Solgaard, O.We present a micromachined scanning probe cantilever, in which a specific higher-order flexural mode is designed to be resonant at an exact integer multiple of the fundamental resonance frequency. We have fabricated such cantilevers by reducing the stiffness of the third order flexural mode relative to the fundamental mode, and we have demonstrated that these cantilevers enable sensing of non-linear mechanical interactions between the atomically sharp tip at the free end of the cantilever and a surface with unknown mechanical properties in tapping-mode atomic force microscopy. Images of surfaces with large topographical variations show that for such samples harmonic imaging has better resolution than standard tapping-mode imaging.Item Open Access Modeling the effect of subsurface interface defects on contact stiffness for ultrasonic atomic force microscopy(AIP Publishing LLC, 2004) Sarioglu, A. F.; Atalar, Abdullah; Degertekin, F. L.We present a model predicting the effects of mechanical defects at layer interfaces on the contact stiffness measured by ultrasonic atomic force microscopy sAFMd. Defects at subsurface interfaces result in changes at the local contact stiffness between the AFM tip and the sample. Surface impedance method is employed to model the imperfections and an iterative algorithm is used to calculate the AFM tip-surface contact stiffness. The sensitivity of AFM to voids or delaminations and disbonds is investigated for film-substrate combinations commonly used in microelectronic structures, and optimum defect depth for maximum sensitivity is defined. The effect of contact force and the tip properties on the defect sensitivity are considered. The results indicate that the ultrasonic AFM should be suitable for subsurface detection and its defect sensitivity can be enhanced by adjusting the applied force as well as by judicious choice of the AFM tip material and geometry.Item Open Access Nanomechanics using an ultra-small amplitude AFM(Cambridge University Press, 2001) Hoffmann, P. M.; Jeffery, S.; Oral, Ahmet; Grimble, R. A.; Özer, H. Özgür; Pethica, J. B.A new type of AFM is presented which allows for direct measurements of nanomechanical properties in ultra-high vacuum and liquid environments. The AFM is also capable to atomic-scale imaging of force gradients. This is achieved by vibrating a stiff lever at very small amplitudes of less than 1 Å (peak-to-peak) at a sub-resonance amplitude. This linearizes the measurement and makes the interpretation of the data straight-forward. At the atomic scale, interaction force gradients are measured which are consistent with the observation of single atomic bonds. Also, atomic scale damping is observed which rapidly rises with the tip-sample separation. A mechanism is proposed to explain this damping in terms of atomic relaxation in the tip. We also present recent results in water where we were able to measure the mechanical response due to the molecular ordering of water close to an atomically flat surface.Item Open Access Noncontact lateral-force gradient measurement on Si(111)-7×7 surface with small-amplitude off-resonance atomic force microscopy(2009) Atabak, M.; Ünverdi O.; Özer H.O.; Oral, A.In this work, the authors report on a quantitative investigation of lateral-force gradient and lateral force between a tungsten tip and Si (111) - (7×7) surface using combined noncontact lateral-force microscopy and scanning tunneling microscopy. Simultaneous lateral-force gradient and scanning tunneling microscopy images of single and multiatomic step are obtained. In our measurement, tunnel current is used as feedback. The lateral-stiffness contrast has been observed to be 2.5 Nm at a single atomic step, in contrast to 13 Nm at a multiatomic step on Si (111) surface. They also carried out a series of lateral stiffness-distance spectroscopy, which show a sharp increase in tip-surface interaction stiffness as the sample is approached toward the surface. © 2009 American Vacuum Society.Item Open Access Sub-Angstrom oscillation amplitude non-contact atomic force microscopy for lateral force gradient measurement(2009) Atabak, M.; Ünverdi O.; Özer H.O.; Oral, A.We report the first results from novel sub-Angstrom oscillation amplitude non-contact atomic force microscopy developed for lateral force gradient measurements. Quantitative lateral force gradients between a tungsten tip and Si(1 1 1)-(7 × 7) surface can be measured using this microscope. Simultaneous lateral force gradient and scanning tunnelling microscope images of single and multi atomic steps are obtained. In our measurement, tunnel current is used as feedback. The lateral stiffness contrast has been observed to be 2.5 N/m at single atomic step, in contrast to 13 N/m at multi atomic step on Si(1 1 1) surface. We also carried out a series of lateral stiffness-distance spectroscopy. We observed lateral stiffness-distance curves exhibit sharp increase in the stiffness as the sample is approached towards the surface. We usually observed positive stiffness and sometimes going into slightly negative region. © 2009 Elsevier B.V. All rights reserved.