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Conductive AFM Probes

Pt coated, DPE (low-noise) and DPER (high-res) AFM Probes
Pt coated AFM tip close-up
Pt coated AFM tip close-up
DPE AFM tip close-up
DPE AFM tip close-up
DPER AFM tip close-up
DPER AFM tip close-up

 

The pyramidal silicon etched AFM probes with an overall conductive platinum coating are suitable for a wide range of electrical AFM applications. The platinum coating is a 30nm thick film on both sides of the AFM cantilever.

The special DPE AFM probes feature silicon AFM tips with a special structure of conductive layers, which provides a more stable electrical signal and less noise. Because of the increased AFM tip radius, some reduction of resolution in the topography image is possible when using DPE AFM probes in comparison with the regular platinum coated AFM probes.

The special DPER AFM probes are made by depositing a thin platinum coating on silicon AFM tips. While the thickness of the coating on a flat AFM cantilever surface is about 15nm, there is only a 10nm increase in the AFM tip dimensions compared to bare silicon AFM probes.

Typical radius of uncoated AFM tip
8nm
Resulting AFM tip radius with the coating
<30nm (Pt coated)
<40nm (DPE)
<20nm (DPER)
Full AFM tip cone angle*
40°
Total AFM tip height
12-18µm
AFM Probe material
n-type silicon
AFM Tip coating
Platinum
Detector coating
Platinum

*The full cone angle may be less than 40° at the last 200nm of the AFM tip end.

 

1 AFM Cantilevers Series

AFM CantileverResonance Frequency, kHzForce Constant, N/m
mintypicalmaxmintypicalmax
14 series 110 160 220 1.8 5.0 13
15 series 265 325 410 20 40 80
16 series 170 190 210 30 45 70
17 series 10 13 17 0.06 0.18 0.40
18 series 60 75 90 1.2 2.8 5.5

 

3 AFM Cantilever Series

AFM CantileverResonance Frequency, kHzForce Constant, N/m
mintypicalmaxmintypicalmax
35 series Cantilever A 130 205 290 2.7 8.9 24
Cantilever B 185 300 430 4.8 16 44
Cantilever C 95 150 205 1.7 5.4 14
36 series Cantilever A 30 90 160 0.1 1.0 4.6
Cantilever B 45 130 240 0.2 2 9
Cantilever C 25 65 115 0.06 0.6 2.7
37 series Cantilever A 30 40 55 0.3 0.8 2
Cantilever B 15 20 30 0.1 0.3 0.6
Cantilever C 20 30 40 0.1 0.4 1




4 AFM Cantilever Series

AFM CantileverResonance Frequency, kHzForce Constant, N/m
mintypicalmaxmintypicalmax
11 series Cantilever A 12 15 18 0.1 0.2 0.4
Cantilever B 60 80 100 1.1 2.7 5.6
Cantilever C 115 155 200 3 7 16
Cantilever D 250 350 465 17 42 90 

Application

The electric properties of different materials can be mapped to the topography images using AFM probes with conductive coatings, when AC or DC bias is applied between the AFM tip and the sample. Contact mode or two-pass operation technique can be used for this purpose. The data can be used for analysis of the structure and composition of heterogeneous samples as well as for quantitative characterization of individual grains or defects on surface.

Though silicon is conducting in bulk due to the presence of the dopants, the surface of the AFM probe is always coated by a thin (1-2nm) native oxide film. That is why using the conductivity of uncoated silicon AFM probes for AFM measurements is possible only in UHV conditions after the oxide film is removed. For imaging the electric properties of materials in ambient conditions, AFM probes with special conducting coatings are usually used.

Platinum coated AFM probes are comonly used for Electrostatic Force Microscopy (EFM) and Kelvin Probe Force Microscopy (KPFM) investigation.

Height image obtained in tapping mode
Height image obtained in tapping mode
EFM map of the same area
EFM map of the same area

Height and phase images of the rubber-modified isotactic polypropylene filled with carbon black. The images were obtained in Electric Force Microscopy mode using HQ:NSC14/Pt AFM probes. Images courtesy of S. Magonov (Bruker).

DPE AFM probes have increased coating thickness, which gives more freedom for using them in contact electrical modes. The AFM probes provide better performance and higher contrast of electrical signals, while the ability to resolve the small surface details might be reduced. The AFM probes can be used in electric AC modes when a study of the electric properties of a sample has higher priority. This is demonstrated in AM-FM images of a fluoroalkane layer.

HQ:DPE-XSC11

The DPER AFM probes can be used for imaging samples with high resolution in XY directions. Due to the thin coating, the electrical signal may be noisy. One should also not expect coating stability in contact or hard tapping regimes of AFM operation.

HQ:DPER-XSC11

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