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hi
Iam usind INNOVA ..when I am takindg contact mode force curves ,whatever is my sample my sensor response is not changing....I am getting similar sensor response for both hard and soft samples..
so please give me an advice how it would happen?
Hi Remya,
The slope of the force-distance curve will only change if your cantilever is actually stiff enough to indent the sample to some extend. Keep in mind that the force a cantilever can exert for a given z-movement is described by Hooke's law. So if you want to see a difference in complience of your sample by evaluating the slope of a force curve you have to choose a cantilever with an appropriate spring constant. This has nothing to do with your machine but rather with your choice of cantilevers.
On the Innova also take advantage of always using the "closed-loop z" option to eliminate z- hysteresis.
Stefan
Hello Remya,
A few things to consider. I am actually curious what you intend to measure on a memebrane. Membranes are usually homogenous so you would not expect any differences in the force curves. Besides that:
1. Make sure that your membrane is supported properly. If it is suspended then you might not indent it at all but just flex the whole piece.
2. Your measurement will depend on the thickness to an extend. I.e. if your memebrane is very thin you might actually push onto the substrate.
3. Make sure to carefully select the area you are attempting your indents. You want to avoid maming an indent in a pore of the mebrane. The "probe positioning (point and shoot)" feature should be used on your Innova.
4. Maybe a TAP150 is a good start. You may want to contact Bruker AFM Probes and ask them for a few samples of cantilevers with different spring constants. This way you can easily figure out which one(s) will give you success.
Good Luck
I am not sure what you are trying to achieve but steel has a Youngs modulus of around 100-200 GPa, Silicon is about in the same range depending on crystal orientation and so forth. So these are not accesible with a TESP tip at all. Our Nanoindention cantilevers are the stiffest ones we make at a k around 350 N/m equipped with a diamond tip but even then you obviously have a limit.
If you want to find out if you really make an indent I would suggest that you pick a rather soft sample and scan a smalla rea, maybe around 500nm - 1um. The make a few indents by executing force curves with various loadings. After that scan the area again and look for the indents. Measuring the indent will also give you additional useful information.
Best,
Remya,
Force curves on Innova can be taken with the z-sensor on (closed-loop) or z-sensor off( open loop), I always recommend using the z-sensor on so running the f-s curve in closed-loop mode. Z-start denotes the position (typically away from the surface) whenre the probe starts its z-curve. The convention here is that a neagtive sign means aways from the surface. Z-end is the position closest to the surface before the probe retracts again. There are two things to consider: