Atomic Force Microscopy (AFM)
WITec alpha300A
In atomic force microscopy (AFM), the force between the sample surface and a sharp tip is measured to elucidate the surface structure and mechanical properties. To do so, the AFM tip is typically attached to a cantilever, which bends depending on the force acting on the tip according to Hook’s law. The cantilever deflection is then measured by reflecting a laser off the backside of the cantilever onto a position sensitive photo diode. In the contact mode, an image of the surface structure is obtained by scanning the tip over the surface while maintaining a constant tip-sample force, i.e., a constant deflection of the cantilever.
However, for delicate samples AFM measurements in contact mode are not optimal because the rather low force sensitivity of this mode requires the tip to be in close contact with the surface during the whole measurement. Hence, the tip is continuously dragged over the surface, which can potentially damage the sample. Instead, dynamic AFM modes – especially the so-called tapping or intermittent contact mode – were developed. In these modes of operation, the cantilever is excited to oscillate at or close to its resonance frequency. Due to the oscillation, the tip is only in contact with the surface briefly, decreasing the friction forces on the sample. The intermittent contact mode is the most commonly used mode for investigating samples under ambient conditions.
The WiTec Alpha 300 A instrument supports AFM measurements in both contact and intermittent contact mode as well as measurements in the so-called pulse force mode. Furthermore, the AFM measurements can be combined with optical microscopy and laser spectroscopy.
Possible applications
- Characterization of surface topography and mechanical properties of metallic and insulating samples
- Investigation of delicate samples with dynamic AFM in the tapping / intermittent contact mode
- Determination of local mechanical material properties (stiffness, adhesion and viscosity) with the pulse force mode
- Measurement of images, line scans and force distance curves
- Combination with optical spectroscopy for scanning near field optical microscopy (SNOM), tip enhanced Raman spectroscopy (TERS) or correlated Raman imaging.
Terms of use and usage fees
This device can be used autonomously after successful training.
To be authorised to use this device, you must pass the following tests:
- General Safety Guidelines for Faculty Members
- Laboratory Safety
- Laser Safety
| User group | Hourly Rate | Cost per AFM Cantilever | Note |
|---|---|---|---|
| Faculties of Physics and Chemistry | - | - | 1. |
| Vienna Life Science Instruments | 12 € | 40 € | 2., 3. |
| University users | 25 € | 40 € | 2., 3. |
| Non-university users | 50 € | 40 € | 2. |
Measurements on one sample may need more than one cantilever.
- You will need to buy the AFM contilevers yourself.
- We will buy AFM cantilevers for you. They might be useable for more than one sample.
- Under a publication agreement, the hourly rate is waived.
We also charge for the costs of our staff for training sessions and measurements that cannot be carried out independently.
| User group | Hourly Rate for the Operator | Note |
|---|---|---|
| Faculties of Physics and Chemistry | - | |
| Vienna Life Science Instruments | 70 € | 1. |
| University users | 70 € | 1. |
| Non-university users | 100 € |
- Under a publication agreement, the hourly rate for our employees is also waived.
Specifications
| Device Parameter | Value or Range |
|---|---|
| Sensor | Cantilever |
| Sensor Design | WiTec Cantilever with mounting ring |
| Detection Method | Optical (Beam deflection) |
| Scan Area | 100 µm x 100 µm x 20 µm |
| Scan Accuracy | lateral: < 1 nm; vertical: < 0.2 nm |
| Measurement Modes | Contact, intermittent contact (tapping), pulse force |
| Cantilever Excitation | Piezoelectric |
| Software | Basic analysis: WiTec Software. Advanced analysis: Gwyddion |
| Temperature Range | Room temperature up to 200 °C |
Downloads
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