Ashok Kumar Swami In cross-sectional SEM using Focused Ion Beam (FIB)), a focused ion beam mills a trench to expose the film’s edge, followed by low-energy polishing to get a smooth, artifact-free surface. This method gives site-specific, high-resolution cross-sections even for very thin or delicate films.

How did you prepare the cross-section?

What is the material?

What is the layer thickness?

Can you provide an image?

Doing cross-sectional SEM on thin films can be a huge pain, especially if you’re not getting any image. The most common culprit? Sample prep issues or charging effects in the microscope. Let’s start with how to actually prep a sample in a simple, practical way.

Honestly, the easiest method if you don’t have fancy gear (like ion milling machines or microtomes) is the cleaving/fracture technique. Take your sample—let’s say it’s on a glass substrate—and use a diamond scribe to gently score the BACK side (not the thin film side; otherwise, you’ll just crunch and smear that layer!). Then, sandwich the sample between two glass slides for support. Now, here’s the trick: apply a quick, sharp force, even just using your weight (or a controlled tap). It feels risky, but if done right, you get a clean break and a nice cross-section of your film for imaging. I’ve tried sawing, polishing, and all sorts of delicate approaches, but cleaving like this beats them for most brittle substrates. Sawing and grinding often just wipe out ultra-thin layers.

If you’re working with softer films or membranes (think polymers), try the cryo-fracture trick. Dunk the sample in liquid nitrogen for a minute; once it’s brittle, snap it quickly. You can even embed it in a drop of ultrapure water or diluted sucrose, freeze it, then slice thin sections with a cryostat at −30°C. That gives crazy-smooth, undamaged cross-sections—awesome for soft stuff and layered membranes.

For those who have access, ion milling is the gold standard. After you’ve done your rough section, use an ion mill to “polish” the cross-section. The result? Super-pristine, flat surfaces, ready for high-res SEM. But most of us don’t have this kit lying around.

Sometimes folks suggest embedding in epoxy and polishing—but heads-up, that’s only for thick and mechanically tough films. For nanometer-scale layers, you’ll just destroy them with polishing and grinding. So avoid that for “really thin” stuff.

Now, mounting: always orient the cross-section upright, so the electron beam can scan directly across your layers. And if your sample/substrate is non-conductive, you pretty much have to sputter-coat it with a thin layer of gold, platinum, or carbon. That’s how you avoid tons of charging and blank screens in SEM.

Final imaging tips: run your SEM at a lower voltage (2–5kV) and, if you can, use a low-vacuum mode. High voltage is charging central. Backscattered electron mode is great for seeing composition differences, and if you have EDS, you can pinpoint elements in each layer.

So, if you’re not getting any image, I’d bet it’s a combo of: rough or smeared cross-section (try the cleaving or cryo method), sample not coated (sputter coat it), or trying to image at high voltage. Fixing those will get you on track. And hey, even experienced folks have these headaches—just keep tweaking your prep until you get a clean break and a conductive surface. After that, imaging should be way easier!

I am attaching a document file here, and I hope it will be helpful to you in some way