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|style="background:LightGrey; color:black"|[[#Height Accuracy|Height (z) accuracy]]
|style="background:LightGrey; color:black"|[[#Height Accuracy|Height (z) accuracy]]
|style="background:WhiteSmoke; color:black"|better than 2% (at 200 nm), typically better then 0.75%
|style="background:WhiteSmoke; color:black"|better than 2% (at 200 nm), typically better than 0.75%
|style="background:WhiteSmoke; color:black"|better than 2% (at 200 nm), typically better then 0.75%
|style="background:WhiteSmoke; color:black"|better than 2% (at 200 nm), typically better than 0.75%
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===Height Accuracy===
===Height Accuracy===
Heigh accuracy estimations in AFM measurements are complex and depends on the scale you are interested in. At sub nanometer scale or a few nanometers the height measurement may be affected by the properties of the cantilever tip, your sample material stiffness and the scanning force. These parameters are less important when measuring in the 100 nm range and above. At all scales calibration of the Z-piezo is important.  
Height accuracy estimations in AFM measurements are complex and depends on the scale you are interested in. At sub nanometer scale or a few nanometers the height measurement may be affected by the properties of the cantilever tip, your sample material stiffness and the scanning force. These parameters are less important when measuring in the 100 nm range and above. At all scales calibration of the Z-piezo is important.  


Here at DTU Nanolab we calibrate the Z-piezo with a certified sample that is approximately 200 nm in height. This sample height is given with an uncertainty that is calculated based on variation on the calibration sample and measurement uncertainties of the instrument used for certification. The uncertainty on the calibration sample is ≤ 1.5 nm. Following our QC procedure we accept an offset from the certified value of 2%. For a 200 nm sample this is 4 nm.  If we use the formula for combined uncertainties then the uncertainty is: 4.3 nm or 2.1%
Here at DTU Nanolab we calibrate the Z-piezo with a certified sample that is approximately 200 nm in height. This sample height is given with an uncertainty that is calculated based on variation on the calibration sample and measurement uncertainties of the instrument used for certification. The uncertainty on the calibration sample is ≤ 1.5 nm. Following our QC procedure we accept an offset from the certified value of 2%. For a 200 nm sample this is 4 nm.  If we use the formula for combined uncertainties then the uncertainty is: 4.3 nm or 2.1%
However when we check the value it is typically less then 1% off given a combined uncertainty of: 0.75%
However when we check the value it is typically less then 1% off given a combined uncertainty of: 0.75%
===Tip status===
''This section is written by Jesper Pan @DTU Nanolab
When measuring a sample using an AFM, the resulting image is the convolution of the tip shape and sample shape.
As the tip is used, it will become less sharp, thus the resulting image appear blurry.
This effect is especially visible when imaging samples with sharp/edged features, and drastically change roughness parameters like R<sub>max</sub>, R<sub>q</sub> and R<sub>a</sub>. Therefore it is important to be able to identify a worn tip.
The figure below shows a comparison of the [https://www.budgetsensors.com/sample-for-tip-evaluation-tipcheck TipCheck sample].
The left image shows a worm tip scanning across a rough surface with sharp edges. Due to tip convolution you practically use the sample to measure the shape of the tip. In this case, the tip is an oval pointing towards the top left, which causes all features to look like that. Furthermore, the worn tip is too big to reach bottom of the trenches between the structures. Which result in a lower measured roughness and Z-range.
{| class="wikitable" style="max-width:800px"
|+ Comparison between images of the Tip Checker sample
|-
! !! Worn Probe !! New probe
|-
! Image
| [[File:AFMWornTip.jpg|thumb|left|alt=Image taken using a worn probe| AFM image of the tip checker sample taken using a worn AFM probe]]
| [[File:AFMNewTip.jpg|thumb|left|alt=Image taken using a new probe| AFM image of the tip checker sample taken using a new AFM probe]]
|-
! Image Parameters
|
* Scan mode: PeakForce Tapping
* Probe: Tap 150Al
* Size: 1µm
* Scan Speed: 1Hz
* Samples/line: 256
|
* Scan mode: PeakForce Tapping
* Probe: Tap 150Al
* Size: 1µm
* Scan Speed: 1Hz
* Samples/line: 256
|-
! Roughness information
|
* R<sub>q</sub>: 2.49 nm
* R<sub>a</sub>: 1.97 nm
* R<sub>max</sub>: 18.8 nm
|
* R<sub>q</sub>: 10.5 nm
* R<sub>a</sub>: 8.45 nm
* R<sub>max</sub>: 78.3 nm
|-
! Comments
| The shape of the probe causes all features to look like an oval pointing towards the top left of the image. Low measured roughness as the worn tip skates across the top of the triangles.
| Same sample taken with a new probe. The triangular structures are pointing in different directions. Higher measured roughness as the sharper tip can map the trenches between the triangles.
|}
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