title: Wideband digital frequency detector with subtraction-based phase comparator for frequency modulation atomic force microscopy.
abstract: We have developed a wideband digital frequency detector for high-speed frequency modulation atomic force microscopy (FM-AFM). We used a subtraction-based phase comparator (PC) in a phase-locked loop circuit instead of a commonly used multiplication-based PC, which has enhanced the detection bandwidth to 100 kHz. The quantitative analysis of the noise performance revealed that the internal noise from the developed detector is small enough to provide the theoretically limited noise performance in FM-AFM experiments in liquid. FM-AFM imaging of mica in liquid was performed with the developed detector, showing its stability and applicability to true atomic-resolution imaging in liquid.
authors.affiliation: Department of Electrical and Computer Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Mitani
authors.forename: Mamoru
authors.initials: M
authors.lastname: Kubo
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Muramoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fukuma