There is a new page here, which is about the recently set up AFM labs in my research institute, Requimte. The page has location, booking information, etc about the labs. But it also has operation protocols for the instruments, so might also be of use for other users of the TTAFM from AFMWorkshop. There are also some example images collected on the two machines, on their individal pages, Long Beach and Signal Hill. The page can be reached directly at afmhelp.com/requimte.
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RQUIMTE AFM TWIN LAB
This page has contact information, locations, and other useful information about the AFM instruments in the AFM TwinLabs located in Requimte labs in Porto and Lisbon, Portugal.
This page is intended for users and potential users of the instruments; for more information about Atomic Force Microscopy (AFM), see the links on the left. The two labs are equipped with TTAFM instruments from AFM Workshop.
The Porto AFM Workshop 2016 has finished recently, it ran from the from the 18th April to 21st April. This is a training workshop, aimed at any researcher or scientist, who wants to learn about AFM, or increase their knowledge of the technique. Following the successful courses that ran in 2011, 2013 and 2014, the course will included several hours hands-on training in acquiring images with the atomic force microscope as well as AFM data processing. As well as lectures on practical classes, the course featured advanced topics lectures from guest scientists in biology and materials science.
A report on the course was published here recently and the results from the image competition we ran will be announced soon!
|Lisbon lab: Signal Hill|
|For further details about the facilities in the Porto lab click here or click on the picture above.||For further details about the facilities in the Lisbon lab click here or click on the picture above.|
This site allows users to access instrument specifications and locations, as well as contacts of the two supervisors of the Requimte AFM Twin-lab
· See booking schedule, make bookings at the Twin-lab – for registered users of the instruments only.
· When available you will also see the schedule for Requimte AFM mini-course, and sign-up
· Currently in development: Our protocols for sample preparation, image acquisition, image processing, image analysis. These materials are specifically designed for the individual Requimte instruments. Currently the following procedures are available:
· You can use the following links to download the software required to process the images from the Requimte instruments. This software is Gwyddion, which can be found at Gwyddion.net. There is a user guide for this software here. It is recommended to use version 2.22 or above of Gwyddion. For other AFM/SPM software, look here: SPM Software.
· To access materials specific to one of the labs, click on the lab you are interested in above.
The locations of the two AFM labs in the TWINLAB are shown on a google map linked to below. Click the markers on the map for full address details. Contact details can be found on the pages describing the two instruments linked above (click on the instrument pictures).
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A couple of new details about my book, Atomic Force Microscopy. Firstly, I just found a new (to me) review (published in German in Physik Magazine), including this great quote:
"Atomic Force Microscopy by Peter Eaton and Paul West is the manual that should accompany any AFM."
Prof. Othmar Marti, University of Ulm
Secondly, a new paperback edition of the book, was recently published. In addition to being approximately half the price of the hardback edition, this new edition has been updated and all (known) typos corrected, so this is the version to get if you can!
The paperback version can be found on amazon.com here.
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While many other procedures are important for full determination of the performance of an AFM instrument, the Z noise floor is often used as a simple parameter to quantify instrument performance, since it indicates the lower limit of the precision that can be reached in the z axis in that instrument, and is also simple to measure.
It can be essential to know the noise floor of the AFM instrument to assure that high resolution measurements are meaningful. This can be particularly important for measurements of very small features (i.e. < 5nm), and for high resolution force spectroscopy. Measuring the noise floor can also help in optimizing instrument setup and vibration isolation. It is important to know the noise floor when using only the z piezo in the z feedback loop, as well as the noise floor of the z calibration sensor if there is one in the instrument. In most instruments, the noise floor of the z calibration sensor will be much higher than that of the z piezo.
In order to get reproducible results, all scan parameters should be maintained the same when comparing two results. Some factors, such as the PID values vary greatly from instrument to instrument, so the specific values to use cannot be suggested here. In each case, standard values should be established such that a fair comparison can be made.
Note that the procedure below is adapted from general guidelines given in Appendix B, page 195 of Eaton and West “Atomic Force Microscopy”. For a outline of a procedure that’s generally applicable to any model of AFM, take a look at the procedure below. Click here to find a specific procedure for measuring the z noise floor on a TT-AFM from AFM workshop.
Measuring noise floor in the z piezo signal
a) Place a flat, clean sample in the instrument. Use a new probe.
b) Do a probe approach and scan a small image on the sample to verify cleanliness and optimize the PID parameters.
c) Set the instrument to make a zero size scan such that the probe does not move in the x and y axis. Some instruments do not seem to have the option to do this (I have found that the JPK Nanowizard software does not allow this). In this case, make the smallest size scan you are able to , such as 1nm, or even less if possible).
d) Measure an image without probe motion in x or y, i.e. an image with a scan size of 0 nm, at a 1 Hz scan rate. A 128 x 128 pixel image is adequate. The data from the z piezo voltage should be used. This may be labelled height, or topography. The z scale should be in nanometers.
e) It may be necessary to flatten the data before the measurement, e.g. by a 1st order horizontal line levelling routine.
f) Calculate the RMS roughness (Rq, see chapter 5) of the image, this value is the noise floor.
If you get some transient noise in the image, from e.g. a person talking, or slamming a door, you can repeat the image.
The achievable noise floor varies from one instrument to another, as well as depending on the noise in the environment, the measurement parameters, and the vibration isolation, but typically a sub-Ångström noise floor can be achieved. An example of type of image you should get is shown in the image above. it's important that you scan a small image before doing the "zero size" image, as the instrument must be in feedback for the noise floor to be measured.
All text and images copyright Peter Eaton 2014-2018
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There are a wide variety of technique available to make these kind of measurements nowadays, however, microscopy is often used, because it is a direct technique (some other techniques measure properties related to size), and because it’s also possible to measure shape at the same time. The size of nanoparticles is extremely important for their properties, and ideally a technique to measure nanoparticle size will have sub-nanometer resolution.
Apart from microscopy, light-scattering techniques are probably the most common techniques used. The method of dynamic light scattering, or DLS; is extremely popular and used in thousands of labs worldwide. A newer method based on laser light scattering, called nanoparticle tracking analysis, or NTA, is currently growing in popularity.
In our project, we prepared nine samples; these we made up of nanoparticles composed of three different, and commonly used materials, a metal, an oxide (silica), and a polymer. We examined each materials in two different sizes, and also tested the ability of each method to distinguish between different populations in mixed samples.
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