Now showing 1 - 3 of 3
  • Publication
    Direct measurement of periodic electric forces in liquids
    (American Institute of Physics, 2008-01-07) ; ; ;
    The electric forces acting on an atomic force microscope tip in solution have been measured using a microelectrochemical cell formed by two periodically biased electrodes. The forces were measured as a function of lift height and bias amplitude and frequency, providing insight into electrostatic interactions in liquids. Real-space mapping of the vertical and lateral components of electrostatic forces acting on the tip from the deflection and torsion of the cantilever is demonstrated. This method enables direct probing of electrostatic and convective forces involved in electrophoretic and dielectroforetic self-assembly and electrical tweezer operation in liquid environments.
      251Scopus© Citations 8
  • Publication
    High frequency piezoresponse force microscopy in the 1-10 MHz regime
    (American Institute of Physics, 2007-12-04) ; ; ;
    Imaging mechanisms in piezoresponse force microscopy (PFM) in the high frequency regime above the first contact resonance are analyzed. High frequency (HF) imaging enables the effective use of resonance enhancement to amplify weak signals, improves the signal to noise ratio, minimizes the electrostatic contribution to the signal, and improves electrical contact. The limiting factors in HF PFM include inertial stiffening, deteriorating signal transduction, laser spot effects, and the photodetector bandwidth. Analytical expressions for these limits are derived. High-quality PFM operation in the 1-10 MHz frequency range is demonstrated and prospects for imaging in the 10-100 MHz range are discussed. (c) 2007 American Institute of Physics.
      351Scopus© Citations 25
  • Publication
    Fabrication, dynamics, and electrical properties of insulated scanning probe microscopy probes for electrical and electromechanical imaging in liquids
    (American Institute of Physics, 2007-08-30) ; ; ;
    Insulated cantilever probes with a high aspect ratio conducting apex have been fabricated and their dynamic and electrical properties analyzed. The cantilevers were coated with silicon dioxide and a via was fabricated through the oxide at the tip apex and backfilled with tungsten to create an insulated probe with a conducting tip. The stiffness and Q factor of the cantilevers increased after the modifications and their resonances shifted to higher frequencies. The coupling strength between the cantilever and the coating are determined. Electromechanical imaging of ferroelectric domains, current voltage probing of a gold surface, and a probe apex repair process are demonstrated.
      322Scopus© Citations 24