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Publication Citation: Spring constant calibration of AFM cantilevers with a piezosensor transfer standard

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Author(s): Eric Langlois; Gordon A. Shaw; John A. Kramar; Jon R. Pratt; Donna C. Hurley;
Title: Spring constant calibration of AFM cantilevers with a piezosensor transfer standard
Published: September 24, 2007
Abstract: We describe a method to calibrate the spring constants of cantilevers for atomic force microscopy (AFM). The method makes use of a piezosensor comprised of a piezoresistive cantilever and  accompanying electronics. The piezosensor was calibrated before use with an absolute force standard, the NIS Telectrostatic force balance (EFB). In this way, the piezosensor acts as a force transfer standard traceable to the International System of Units (SI). Seven single-crystal silicon cantilevers with rectangular geometries and nominal spring constants from 0.2N/m to 40N/m were measured with the piezosensor method. The values obtained for the spring constant were compared to measurements by four other techniques: the thermal noise method, the Sader method, force loading by a calibrated nanoindentation load cell, and direct calibration by force loading with the EFB. Results from different methods for the same cantilever were generally in agreement, but differed by up to 300% from nominal values. When used properly, the piezosensor approach provides spring-constant values that are accurate to ±5%. Methods such as this will improve the ability to extract quantitative information from AFM methods.
Citation: Review of Scientific Instruments
Keywords: AFM cantilever calibration; atomic force microscopy; force calibration; spring constant
Research Areas: Metrology
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