Nanoscale Stripes

In a nod to what I used to do, a blog post caught my eye. It regards a bit of a controversy in a field I used to be quite familiar with; nanoscale surface science. The question basically boils down to whether the “stripes” being seen on a very small scale in a STM image are real or some sort of artefact. Given I’ve spent quite a bit of time thinking about the strange things can happen when performing probe microscopy (my masters dissertation has quite a lot of space dedicated to consideration of hysteresis loops in AFM imaging—sorry, no idea where to find an electronic copy of that just now) it’s tickled my fancy.

I vaguely remember maybe seeing a talk on this back in the day (possibly before results were published; or maybe on something entirely else. The memory isn’t what it used to be, and I obviously wasn’t paying too close attention). I didn’t realise there was a controversy though. I’ve no particular stake in this these days, and certainly have been out the game long enough not to have followed all the arguments and counter-arguments enough to form a firm opinion. However, it does sound as if someone is at least fooling themselves. I think it’s worth quoting Phil Moriarty’s guest post, which is well worth a read in full but this stuck with me (emphasis mine):

First, a large scale (80 x 80 nm2) STM image of the nanoparticle layer was taken (using, in this case, an ultrahigh vacuum STM) […] Instead of then reducing the scan area to get a higher resolution/higher magnification image, Yu and Stellacci instead carry out what is sometimes called an “offline zoom”: they simply zoom in on a region of interest (shown by the blue box) using image processing software. This is a rather unorthodox strategy. The usual approach would be to zoom-in in “real time” on the area of interest.

I must say if it were my experiment my instinct would be to take a couple more images of the same area (possibly varying scan conditions, though maybe I’d leave that for the repeat experiments) then decrease the scan area centred on the feature of interest. It seems inconceivable that they wouldn’t even try that which begs the question: Did they simply then not see the feature, or were they unable to get a clear scan? The two are quite possibly very different things.

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