Masters Theses


"Tapping mode (TM) AFM is a popularly used AFM technique in which an oscillating sharp tip mounted on a micro cantilever is used to probe the surface of interest with nanoscale resolution by making intermittent (tapping) contact with the surface. Any change in surface profile affects the tip amplitude, and is detectable only if it results in an amplitude change that is significant enough to be measured by the laser detector. Hence, it is desirable to have a micro cantilever that is sensitive to surface changes so as to provide sharper images and better surface resolution.

In the first part of this thesis, a novel method to improve the measurement sensitivity of the cantilever has been proposed. In this method a driving signal composed of two harmonics is used to generate a tapping trajectory whose valley is broader compared to conventional sinusoidal trajectory. Such a trajectory reduces the velocity of tapping and allows the tip to spend more time in proximity to the sample. Numerical analysis indicates reduction in impact forces and improvement in measurement sensitivity. Experimental results demonstrate increase in image sharpness and reduction in tip wear.

In the second part of this thesis, a new cantilever design, called a “bi-harmonic” cantilever is presented. This cantilever design has a second resonant frequency twice its first resonant frequency, and can be fabricated from commercial cantilevers through silicon etching. Numerical results indicate this cantilever assists in obtaining better sensitivity using a smaller input drive force, compared to commercial cantilevers. Surface images obtained using bi-harmonic cantilevers exhibit improved surface tracking, and thus sharper imaging, which is a direct benefit of higher sensitivity"--Abstract, page iv.


Bristow, Douglas A.

Committee Member(s)

Landers, Robert G.
Sarangapani, Jagannathan, 1965-


Mechanical and Aerospace Engineering

Degree Name

M.S. in Mechanical Engineering


Missouri University of Science and Technolog. Materials Research Center


Missouri University of Science and Technology

Publication Date


Journal article titles appearing in thesis/dissertation

  • Measurement sensitivity improvement in tapping-mode atomic force microscopy through bi-harmonic drive signal
  • Bi-harmonic cantilever design for improved measurement sensitivity in tapping-mode atomic force microscopy


x, 45 pages

Note about bibliography

Includes bibliographical references.


© 2012 Muthukumaran Loganathan, All rights reserved.

Document Type

Thesis - Open Access

File Type




Subject Headings

Atomic force microscopy
Image processing -- Mathematical models
Surfaces (Technology) -- Analysis

Thesis Number

T 10559

Print OCLC #


Electronic OCLC #