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Title: Effect of contact stiffness on wedge calibration of lateral force in atomic force microscopy

Abstract

Quantitative friction measurement of nanomaterials in atomic force microscope requires accurate calibration method for lateral force. The effect of contact stiffness on lateral force calibration of atomic force microscope is discussed in detail and an improved calibration method is presented. The calibration factor derived from the original method increased with the applied normal load, which indicates that separate calibration should be required for every given applied normal load to keep the accuracy of friction measurement. We improve the original method by introducing the contact factor, which is derived from the contact stiffness between the tip and the sample, to the calculation of calibration factors. The improved method makes the calculation of calibration factors under different applied normal loads possible without repeating the calibration procedure. Comparative experiments on a silicon wafer have been done by both the two methods to validate the method in this article.

Authors:
;  [1]
  1. School of Mechanical and Electronic Engineering, Harbin Institute of Technology, Harbin 150001 (China)
Publication Date:
OSTI Identifier:
20953424
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 78; Journal Issue: 4; Other Information: DOI: 10.1063/1.2720723; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ACCURACY; ATOMIC FORCE MICROSCOPY; CALIBRATION; FLEXIBILITY; FRICTION; NANOSTRUCTURES; SEMICONDUCTOR MATERIALS; SILICON

Citation Formats

Wang Fei, and Zhao Xuezeng. Effect of contact stiffness on wedge calibration of lateral force in atomic force microscopy. United States: N. p., 2007. Web. doi:10.1063/1.2720723.
Wang Fei, & Zhao Xuezeng. Effect of contact stiffness on wedge calibration of lateral force in atomic force microscopy. United States. doi:10.1063/1.2720723.
Wang Fei, and Zhao Xuezeng. Sun . "Effect of contact stiffness on wedge calibration of lateral force in atomic force microscopy". United States. doi:10.1063/1.2720723.
@article{osti_20953424,
title = {Effect of contact stiffness on wedge calibration of lateral force in atomic force microscopy},
author = {Wang Fei and Zhao Xuezeng},
abstractNote = {Quantitative friction measurement of nanomaterials in atomic force microscope requires accurate calibration method for lateral force. The effect of contact stiffness on lateral force calibration of atomic force microscope is discussed in detail and an improved calibration method is presented. The calibration factor derived from the original method increased with the applied normal load, which indicates that separate calibration should be required for every given applied normal load to keep the accuracy of friction measurement. We improve the original method by introducing the contact factor, which is derived from the contact stiffness between the tip and the sample, to the calculation of calibration factors. The improved method makes the calculation of calibration factors under different applied normal loads possible without repeating the calibration procedure. Comparative experiments on a silicon wafer have been done by both the two methods to validate the method in this article.},
doi = {10.1063/1.2720723},
journal = {Review of Scientific Instruments},
number = 4,
volume = 78,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • Calibration of lateral forces and displacements has been a long standing problem in lateral force microscopies. Recently, it was shown by Wagner et al. that the thermal noise spectrum of the first torsional mode may be used to calibrate the deflection sensitivity of the detector. This method is quick, non-destructive and may be performed in situ in air or liquid. Here we make a full quantitative comparison of the lateral inverse optical lever sensitivity obtained by the lateral thermal noise method and the shape independent method developed by Anderson et al. We find that the thermal method provides accurate resultsmore » for a wide variety of rectangular cantilevers, provided that the geometry of the cantilever is suitable for torsional stiffness calibration by the torsional Sader method, in-plane bending of the cantilever may be eliminated or accounted for and that any scaling of the lateral deflection signal between the measurement of the lateral thermal noise and the measurement of the lateral deflection is eliminated or corrected for. We also demonstrate that the thermal method may be used to characterize the linearity of the detector signal as a function of position, and find a deviation of less than 8% for the instrument used.« less
  • Proper force calibration is a critical step in atomic and lateral force microscopies (AFM/LFM). The recently published torsional Sader method [C. P. Green et al., Rev. Sci. Instrum. 75, 1988 (2004)] facilitates the calculation of torsional spring constants of rectangular AFM cantilevers by eliminating the need to obtain information or make assumptions regarding the cantilever's material properties and thickness, both of which are difficult to measure. Complete force calibration of the lateral signal in LFM requires measurement of the lateral signal deflection sensitivity as well. In this article, we introduce a complete lateral force calibration procedure that employs the torsionalmore » Sader method and does not require making contact between the tip and any sample. In this method, a colloidal sphere is attached to a 'test' cantilever of the same width, but different length and material as the 'target' cantilever of interest. The lateral signal sensitivity is calibrated by loading the colloidal sphere laterally against a vertical sidewall. The signal sensitivity for the target cantilever is then corrected for the tip length, total signal strength, and in-plane bending of the cantilevers. We discuss the advantages and disadvantages of this approach in comparison with the other established lateral force calibration techniques, and make a direct comparison with the 'wedge' calibration method. The methods agree to within 5%. The propagation of errors is explicitly considered for both methods and the sources of disagreement discussed. Finally, we show that the lateral signal sensitivity is substantially reduced when the laser spot is not centered on the detector.« less
  • A new and simple calibration method for atomic force microscopy (AFM) is developed. This nonscanning method is based on direct force balances on surfaces with known slopes. The lateral force calibration is performed during force-distance measurements for normal force calibration. This method requires a substrate with known slopes, the z motion of the piezocalibrated, and the normal spring constant known. This technique determines not only the lateral detector sensitivity (N/V) but also the detector offset (V/m) and off-centering angle ({alpha}) for asymmetric cantilever-tip geometries. Because it is nonscanning, the AFM cantilever can be calibrated without dulling the tip.
  • We present here a method to calibrate the lateral force in the atomic force microscope. This method makes use of an accurately calibrated force sensor composed of a tipless piezoresistive cantilever and corresponding signal amplifying and processing electronics. Two ways of force loading with different loading points were compared by scanning the top and side edges of the piezoresistive cantilever. Conversion factors between the lateral force and photodiode signal using three types of atomic force microscope cantilevers with rectangular geometries (normal spring constants from 0.092 to 1.24 N/m and lateral stiffness from 10.34 to 101.06 N/m) were measured in experimentsmore » using the proposed method. When used properly, this method calibrates the conversion factors that are accurate to {+-}12.4% or better. This standard has less error than the commonly used method based on the cantilever's beam mechanics. Methods such of this allow accurate and direct conversion between lateral forces and photodiode signals without any knowledge of the cantilevers and the laser measuring system.« less