Scanning probe microscopy (SPM) is an exciting family of techniques applied to everything from materials science to biology. It is defined by the Royal Microscopy Society as “a family of techniques… a physical probe is positioned within a few nanometres of the surface, or in contact with the surface, and the probe is raster-scanned across the surface. A physical property of the surface, to which the probe is sensitive, is used as a control parameter to yield a true 3-dimensional image of the surface.” Through this definition we can see that SPM can cover a wide range of techniques designed to investigate a variety of properties including electrical and electrochemical properties, thermal properties, magnetic properties and more.
SPM is, however, often narrowed to focus only on Atomic Force Microscopy (AFM). To do so seems to limit the full toolkit available when all SPM techniques are considered. By narrowing our focus only to AFM we forget about all of the SPM techniques which allow us to characterize samples in ways not possible with AFM. Take Scanning ElectroChemical Microscopy (SECM) as an example. Using SECM we can measure the local electrochemical activity of a sample with chemical selectivity, as well as the local impedance of a sample. These sorts of measurements are intrinsic to the technique allowing it to answer questions which may have been closed off to AFM alone.
Is it too limiting to only consider AFM when discussing SPM? What SPM techniques deserve to be discussed more?
I think the reason that SPM is narrowed to AFM so often is due to the growth and development that AFM has undergone compared to all the other techniques under the SPM umbrella.
Today a new AFM could do morphology, conductivity, adhesion, stiffness, thermal conduction/expansion, electrochemical, STS, work function, and even IR/Ramen mapping! Not to mention the highest resolution SPMs are AFM and AFM is a benchtop technique without the need for a UHV chamber. Not to mention that AFM is generally more stable that STM over time.
I personally love STM and I desperately would like to work full time with a 4-probe STM but I honestly think that in 40 years the only SPM anyone will use outside of old labs will be AFM.
Hi Sam,
I guess it depends on the field you are working in what SPM means to people. I agree that SPM really is a zoo or category of experiments and not limited to AFM. For example, SPM also includes Scanning Tunneling Microscopy (STM), SPELS (Scanning Probe Energy Loss Spectroscopy) and TERS (Tip-enhanced Raman spectroscopy). But these are less relevant for biological samples. On the other hand, since I'm usually not working with biological samples I wouldn't think first of SECM when talking about SPM.
You have to define the scope or context of the discussion for which you want to create this list of techniques. For a general list of some techniques see the english wikipedia to SPM for a start.
Thanks Karl Bauer & Christopher Goodwin .
That's an interesting take on it, I hadn't thought to consider that SPM means different things to different fields of researchers.
As some context I started thinking about this during a recent SPM conference. I've done some AFM, but my work has never really focused on it. Instead I've used STM, and now the different scanning probe electrochemistries. I was surprised to find that when discussing SPM only two talks over two days looked at anything other than AFM (STM and NSOM). Which leads to the rhetorical question of when there's such a wide range of other scanning probe options is AFM always the right choice or are there times where this isn't necessarily the case but its what people know?
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