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Electric Techniques

Electric Techniques Overview

Rev. D Dimension 3100 Manual 273

16.1 Electric Techniques Overview

There are two types of electric techniques used with the Dimension 3100: Electric Force

Microscopy (EFM) and Surface Potential Detection.

Electric techniques are similar to magnetic force microscopy (MFM) and share many of the same

procedural techniques. Electric techniques and MFM both use the Interleave and LiftMode

procedures. The two-pass LiftMode measurement allows the imaging of relatively weak but long-

range magnetic and electrostatic interactions while minimizing the inﬂuence of topography (see

Figure 16.1a). LiftMode records measurements in two passes, each consisting of one trace and one

retrace, across each scanline. First, LiftMode records topographical data in TappingMode on one

trace and retrace. Then, the tip raises to the lift scan height, and performs a second trace and retrace

while maintaining a constant separation between the tip and local surface topography.

Figure 16.1a LiftMode Principles

16.1.1 Electric Force Microscopy Overview

Electric Force Microscopy measures variations in the electric ﬁeld gradient above a sample. The

sample may be conducting, nonconducting, or mixed. Since the surface topography (e.g. sharp

points on the surface concentrate the ﬁeld gradient) shapes the electric ﬁeld gradient, large

differences in topography make it difﬁcult to distinguish electric ﬁeld variations due to topography

or due to a true variation in the ﬁeld source. The best samples for EFM are samples with fairly

smooth topography. The ﬁeld source includes trapped charges, applied voltage, etc. Samples with

insulating layers (passivation) on top of conducting regions are also good candidates for EFM.

All standard Dimension Series SPMs are capable of EFM imaging using amplitude detection

techniques. By adding an Extender electronics module, you can use the Dimension system for

frequency modulation or phase detection with improved results (see Figure 16.1b). Frequency

modulation and phase detection has largely superseded amplitude detection. The Extender

electronics module is required for surface potential imaging, and is strongly recommended for

electric force microscopy.

1521

Electric Fields

Electric Scope Data

Topographic Scope Data

(Main scan)

(Interleave scan)

1. Cantilever measures surface topography on ﬁrst (main) scan.

2. Cantilever ascends to lift scan height.

3. Cantilever follows stored surface topography at the lift height above sample while responding to

electric inﬂuences on second (interleave) scan.

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Dell 3100 Spécifications Page 293