Atomic Force Microscopy

Day 9

AFM - Atomic Force Microscope

Today, I have been show the functions of an AFM, which basically scans the surface of the sample at a nanometre scale, so that any roughness can be seen. A smooth sample is considered to only change its contours by a maximum of 5nm.

First, Dr Ong explained to me the functions of the AFM, how it functions and what it does.
As mentioned above, the AFM is meant to scan the surface of the sample to determine its countours on a nanoscale.

There are 3 ways a AFM can employ the scan the sample:

First, it could be a certain distance away from the sample, and measures the coulomb forces between the sample and the tip of which the AFM uses to scan the sample. The distance from the sample would determine how much force can be measured by the machine, and hence could be used to determine the distance from the tip, allowing the contours to be plotted.

The second method would be to ensure that the tip is always in contact with the sample, such that any contours would change the shape of the tip, and as a laser is shone on the tip, the deflection of the laser by the tip of the sample would be collected by a detector, allowing the machine to know how much the contours have changed, allowing the contours to be plotted as well. This method may not be very good on a soft sample, as it could potentially scratch the sample.

The third method would be to vibrate the tip, and every time the tip contacts the sample the height of the sample could be taken using the same mechanism as the second method. This method would be better used on a soft sample, as it would reduce the damage done to the sample, allowing the true surface to be taken more accurately.

My sample, after the polishing done yesterday, ..., remains a very bad failure in terms of smoothness.



A topography showing an area of my sample

My sample has contours which would measure up to 200nm change, as well as traces of the polishing agent used yesterday, although it look very smooth with the naked eyes. This portion of the sample is part of the same portion shown in yesterday's post (the smoother part).

That concludes the day, and in fact, it concludes the entire research programme for me. If there are any questions or comments, do leave them at the chat box beside and I will respond to them as soon as possible.