Specific Process Knowledge/Characterization/AFM: Atomic Force Microscopy: Difference between revisions
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=AFM Icon 1 & 2 = | =AFM Icon 1 & 2 = | ||
[[Image:P6180008.JPG|right|thumb|300px| AFM Icon-Pt Positioned in clean room: C-1]] | ''This section is written by Berit Herstrøm @DTU Nanolab | ||
[[Image:Foto of system in basement.jpg|right|thumb|300px| AFM Icon-Pt 2 Positioned in the basement of building 346-904]] | [[Image:P6180008.JPG|right|thumb|300px| AFM Icon-Pt Positioned in clean room: C-1, photo: DTU Nanolab internal]] | ||
[[Image:Foto of system in basement.jpg|right|thumb|300px| AFM Icon-Pt 2 Positioned in the basement of building 346-904, photo: DTU Nanolab internal]] | |||
DTU Nanolab has two pieces of Bruker AFM Dimension Icon-Pt. AFM stands for Atomic Force Microscope which is a scanning probe microscope where a sharp probe is scanned across a surface either in contact mode, tapping mode or PeakForce tapping mode. The outcome is a topographic plot of the surface. It has a lateral solution of about 1 nm and a vertical resolution of less than 1 Å which makes it very suitable for topographic characterization in the nanometer regime. The limiting factor however is often the size of the probe in use. The tip radius of curvature (ROC) can be from 2 nm up to more than 20 nm depending on the chosen probe. The half cone angle of the tip can vary from less than 3<sup>o</sup> to over 25<sup>o</sup> giving problems resolving high aspect ratio structures. | DTU Nanolab has two pieces of Bruker AFM Dimension Icon-Pt. AFM stands for Atomic Force Microscope which is a scanning probe microscope where a sharp probe is scanned across a surface either in contact mode, tapping mode or PeakForce tapping mode. The outcome is a topographic plot of the surface. It has a lateral solution of about 1 nm and a vertical resolution of less than 1 Å which makes it very suitable for topographic characterization in the nanometer regime. The limiting factor however is often the size of the probe in use. The tip radius of curvature (ROC) can be from 2 nm up to more than 20 nm depending on the chosen probe. The half cone angle of the tip can vary from less than 3<sup>o</sup> to over 25<sup>o</sup> giving problems resolving high aspect ratio structures. | ||
The main purposes are surface roughness measurements and step/structure high measurements in the nanometer and sub-micrometer regime. For larger structure see the [[Specific Process Knowledge/Characterization/Topographic measurement|topografic measurement]] page. | The main purposes are surface roughness measurements and step/structure high measurements in the nanometer and sub-micrometer regime. For larger structure see the [[Specific Process Knowledge/Characterization/Topographic measurement|topografic measurement]] page. | ||
To get some product information from the vendor take a look at Bruker's homepage [ | To get some product information from the vendor take a look at Bruker's homepage [https://www.bruker.com/en/products-and-solutions/microscopes/materials-afm/dimension-icon-afm.html] | ||
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You can find them here: [https://www.youtube.com/playlist?list=PLjWVU97LayHC9xeoG2uv8IaHuY7t-q0Tj link to training videos] | You can find them here: [https://www.youtube.com/playlist?list=PLjWVU97LayHC9xeoG2uv8IaHuY7t-q0Tj link to training videos] | ||
It is also recommanded to read | It is also recommanded to read this presentation of contract mode, tapping mode and peak force tapping mode [https://labmanager.dtu.dk/view_binary.php?fileId=5383 click HERE - requires login] | ||
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[[Image:Nanoman cantilever AR5.jpg|right|thumb|AR5-NCHR tip<br /> (Aspect Ratio 5)]] | [[Image:Nanoman cantilever AR5.jpg|right|thumb|AR5-NCHR tip<br /> (Aspect Ratio 5)]] | ||
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*[ | *[https://labmanager.dtu.dk/view_binary.php?fileId=5383 Introduction to contact mode, tapping mode and peak force tapping mode + how to improve image quality- requires login] | ||
*[[/AFM Icon Acceptance|AFM Icon Acceptance 1 & 2 and overview of accessories and modes on the systems]] | *[[/AFM Icon Acceptance|AFM Icon Acceptance 1 & 2 and overview of accessories and modes on the systems]] | ||
*[[/Workspaces|What experiment/mode and probe to select]] | *[[/Workspaces|What experiment/mode and probe to select]] | ||
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*Free analysis software: For visualizing and analyzing AFM and Optical profiler files (Nanoman and Sensofar) [http://gwyddion.net Gwyddion] | *Free analysis software: For visualizing and analyzing AFM and Optical profiler files (Nanoman and Sensofar) [http://gwyddion.net Gwyddion] | ||
*or you can install Brukers own software analyses program that can be found on the cleanroom drive: U:\Nlab\CleanroomDrive\_Equipment\AFM\NanoScope_Analysis_x86_v170r1sr2.exe | *or you can install Brukers own software analyses program that can be found on the cleanroom drive: U:\Nlab\CleanroomDrive\_Equipment\AFM\NanoScope_Analysis_x86_v170r1sr2.exe | ||
*or you can get a SPIP license for free if you are connected one of the following institutes (Nanolab, Physics, Chemistry, Mechanics, Energikonvertering, this list may not be updated!) | *or you can get a SPIP license for free if you are connected to one of the following institutes (Nanolab, Physics, Chemistry, Mechanics, Energikonvertering, this list may not be updated!). | ||
==An overview of the performance of the AFM Icon== | ==An overview of the performance of the AFM Icon== | ||
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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 | |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 | |style="background:WhiteSmoke; color:black"|better than 2% (at 200 nm), typically better than 0.75% | ||
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|style="background:silver; color:black"| | |style="background:silver; color:black"| | ||
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===Height Accuracy=== | ===Height Accuracy=== | ||
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 | |||
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! !! Worn Probe !! New probe | |||
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! 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 | |||
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* Scan mode: PeakForce Tapping | |||
* Probe: Tap 150Al | |||
* Size: 1µm | |||
* Scan Speed: 1Hz | |||
* Samples/line: 256 | |||
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* Scan mode: PeakForce Tapping | |||
* Probe: Tap 150Al | |||
* Size: 1µm | |||
* Scan Speed: 1Hz | |||
* Samples/line: 256 | |||
|- | |||
! Roughness information | |||
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* R<sub>q</sub>: 2.49 nm | |||
* R<sub>a</sub>: 1.97 nm | |||
* R<sub>max</sub>: 18.8 nm | |||
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* 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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