THE DEPARTMENT OF AT STATE
UNIVERSITY OF NEW YORK, POTSDAM N.Y.
Learning through research
Electrochemical Quartz Crystal Nanobalance (EQCN) technique utilizes quartz vibrations and piezoelectric effect to measure mass changes as small as a fraction of a monolayer of atoms
Professor Maria Hepel
Atomic Force Microscopy Laboratory
44 Pierrepont Ave.
Potsdam , NY 13676, U.S.A.
AFM tip interaction with sample
(Veeco Nanoscope IIIa)
Force versus distance curve
Atomic Force Measurements
The action at the AFM tip can be viewed as two components:
- a sensor that responds to a force
- a detector that measures the sensor response
F = -kz where F is the force
k is the spring constant of a cantilever and
z is the vertical cantilever displacement.
The spring constant of a cantilever can be expressed as:
k = Et3w/4L3 where E is the elasticity modulus, which is a measure of
the restoring force upon extention,
t is the thickness of the cantilever.
In general, t is difficult to measure, however, it can be determined from the resonance frequency fr:
Fr = 0.162 (E/d)1/2t/L2
where d is the density of the cantilever material.
The values of k are in the range from 0.01 to 50 N/m and are specified by the cantilever manufacturer.
Sharpened AFM Tip End
Nanowires assembled from MoO3 Semiconductor Metal Oxide
AFM Image of a Monolayer Film of Bovine Serum Albumin
on gold EQCN electrode,
film thichness: 38 nm
The AFM/STM instrumentation has been funded by the NSF CCLI program, Award No. 0126402.