title: Wideband phase-locked loop circuit with real-time phase correction for frequency modulation atomic force microscopy.
abstract: We have developed a wideband phase-locked loop (PLL) circuit with real-time phase correction for high-speed and accurate force measurements by frequency modulation atomic force microscopy (FM-AFM) in liquid. A high-speed operation of FM-AFM requires the use of a high frequency cantilever which, however, increases frequency-dependent phase delay caused by the signal delay within the cantilever excitation loop. Such phase delay leads to an error in the force measurements by FM-AFM especially with a low Q factor. Here, we present a method to compensate this phase delay in real time. Combined with a wideband PLL using a subtraction-based phase comparator, the method allows to perform an accurate and high-speed force measurement by FM-AFM. We demonstrate the improved performance by applying the developed PLL to three-dimensional force measurements at a mica/water interface.
authors.affiliation: Frontier Science Organization, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan. fukuma@staff.kanazawa-u.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fukuma
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Yoshioka
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Asakawa
mesh_terms: D021621:Imaging, Three-Dimensional; D018625:Microscopy, Atomic Force / Q000295:instrumentation*; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water