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  • Resonant Frequency [kHz]

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CONTACT MODE AFM PROBES

The mode in which the probe is in close contact with the sample surface is a mode commonly used in atomic force microscopy, and it provides the basis for many other AFM modes. The contact mode uses a micromachined AFM probe mounted on the cantilever. During the scanning process, the afm needle tip and the sample are in constant contact. The force on the tip has an average repulsive force of 10 -9 N. By using a piezoelectric positioning element, the cantilever can be pushed towards the surface of the sample to achieve the purpose of setting the force. In contact mode AFM, the detector signal measuring the deflection of the cantilever in the Z direction is an important parameter. The deflection of the cantilever can be detected by the output signal and compared with some required deflection values in the DC feedback amplifier. If the measured deflection is different from the expected value, the feedback amplifier applies a voltage to the piezoelectric body to restore the desired deflection by changing the distance between the cantilever and the sample. The voltage applied by the feedback amplifier to the piezoelectric is a measure of the height of the surface features of the sample. It is displayed as a function of the lateral position of the sample.

A few instruments operate in UHV, but most instruments operate in the surrounding atmosphere or liquid. The problem with the contact mode is caused by the excessive tracking force applied by the probe to the sample. This effect can be reduced by minimizing the tracking force of the probe on the sample, but in actual operation, there is a practical limit to the amount of force that the user can control. Under actual operating conditions, the surface of the sample is covered with a layer of adsorbed gas composed mainly of water vapor and nitrogen. The thickness of the adsorbed gas is 10 to 30 single layers. When the probe contacts the contaminant layer, a meniscus is formed, and the cantilever is pulled toward the sample surface due to surface tension. The magnitude of the force depends on the details of the probe geometry, but it is usually about 100 nanonewtons. By using probes and part or all of the sample to be completely immersed in the liquid, meniscus forces and other attractive forces can be eliminated. Therefore, operating the AFM with the sample and cantilever immersed in liquid has many advantages. These advantages include eliminating capillary forces, reducing van der Waals forces, and having important technical or biological significance for studying liquid-solid interface. However, working in liquids also involves some disadvantages. These shortcomings include leakage and damage to the hydrated fragile biological samples.

In addition, a large class of samples, including semiconductors and insulators, can capture static charges (partially dissipated and shielded in liquid). This charge can create additional substantial attraction between the probe and the sample. All these forces together define the minimum normal force that can be controllably applied to the sample by the probe. When the probe scans the sample, this normal force generates a large amount of friction. In practice, these frictional forces seem to be more destructive than normal forces and can damage the sample, dull the cantilever probe and distort the resulting data. Also, many samples, such as semiconductor wafers, cannot actually be immersed in liquid. One attempt to avoid these problems is the non-contact mode.

  • Contact Mode-Etched Silicon Probes-1

    CMESP-1
  • Frequency: Nom: 10
  • Spring Const.: Nom: 0.1
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 8nm
  • Material: 0.01 - 0.025 Ωcm Antimony (n) doped Si
  • Contact Mode-Etched Silicon Probes-3

    CMESP-3
  • Frequency: Nom: 40
  • Spring Const.: Nom: 5
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 8nm
  • Material: 0.01 - 0.025 Ωcm Antimony (n) doped Si
  • Contact Mode-Etched Silicon Probes-Al-2

    CMESP-Al2
  • Frequency: Nom: 20
  • Spring Const.: Nom: 0.9
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 8nm
  • Material: 0.01 - 0.025 Ωcm Antimony (n) doped Si
  • Coating: Reflective Aluminum
  • Contact Mode-Etched Silicon Wafer Probes-Al-2

    CMESWP-Al2
  • Frequency: Nom: 20
  • Spring Const.: Nom: 0.9
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 8nm
  • Material: 0.01 - 0.025 Ωcm Antimony (n) doped Si
  • Coating: Reflective Aluminum
  • Contact Mode-Etched Silicon Probes-Al-3

    CMESP-Al3
  • Frequency: Nom: 40
  • Spring Const.: Nom: 5
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 8nm
  • Material: 0.01 - 0.025 Ωcm Antimony (n) doped Si
  • Coating: Reflective Aluminum
  • Contact Mode-Etched Silicon Wafer Probes-Al-3

    CMESWP-Al3
  • Frequency: Nom: 40
  • Spring Const.: Nom: 5
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 8nm
  • Material: 0.01 - 0.025 Ωcm Antimony (n) doped Si
  • Coating: Reflective Aluminum
  • Contact Mode-Etched Silicon Probes-2

    CMESP-2
  • Frequency: Nom: 20
  • Spring Const.: Nom: 0.9
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 8nm
  • Material: 0.01 - 0.025 Ωcm Antimony (n) doped Si
  • 4 Cantilevers Probes-Au

    4CP-Au
  • Frequency: Nom: 65
  • Spring Const.: Nom: 0.35
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 30nm
  • Material: Silicon Nitride
  • Coating: Reflective Gold
  • 4 Cantilevers-Uncoated Probes

    4CUP
  • Frequency: Nom: 65
  • Spring Const.: Nom: 0.35
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 20nm
  • Material: Silicon Nitride
  • AFM-NP-Silicon Nitride AFM Probes-10

    AFMNPSNAP-10
  • Frequency: Nom: 65
  • Spring Const.: Nom: 0.35
  • Geometry: Rotated (Symmetric)
  • Tip Radius: 20nm
  • Material: Silicon Nitride
  • Coating: Reflective Gold
  • Alignment Grooves-Contact Mode Probes

    AGCMP
  • Frequency: Nom: 13
  • Spring Const.: Nom: 0.2
  • Geometry: Standard (Steep)
  • Tip Radius: 7nm
  • Material: 0.01 - 0.025 Ωcm Antimony (n) doped Si
  • Coating: Reflective Aluminum