User`s guide

114
Agilent 5500 SPM
User’s Guide
Agilent Technologies
7
Additional Imaging Modes
Scanning Tunneling Microscopy (STM) 114
Current Sensing AFM (CSAFM) 119
Lateral Force Microscopy (LFM) 123
Dynamic Lateral Force Microscopy (DLFM) 125
Force Modulation Microscopy (FMM) 127
Electrostatic Force Microscopy (EFM) 130
Kelvin Force Microscopy (KFM) 134
One of the primary advantages of the Agilent 5500 SPM is that it allows
you to perform many different imaging modes with the same basic
hardware. Most of the modes presented in this chapter are based on
Contact Mode or AC Mode imaging, so be sure that you have read the
information in Chapter 4, Chapter 5, and Chapter 6 before proceeding
with this chapter.
Scanning Tunneling Microscopy (STM)
In STM, a bias voltage is applied between a sharp, conducting tip and
the sample. When the tip approaches the sample, electrons “tunnel”
through the narrow gap, either from the sample to the tip or vice versa,
depending on the bias voltage. The tunneling current is held constant
throughout the scan. Changes of only 0.1 nm in the separation distance
cause an order of magnitude difference in the tunneling current. The
interaction is between single atoms in the sample and tip, giving STM
remarkably high lateral resolution.
Agilent STM tips are pre-cut or chemically etched lengths of 0.25 mm
OD, 80 % platinum - 20 % iridium wire. If the wire tip is damaged it can
be trimmed and used again. Using tips coated in insulating wax, STM
can also be performed in fluid.
The Agilent multi-purpose scanner, when equipped with an STM nose
assembly (Figure 80), can be used for STM. The nose assembly is