Most of the time, STM and epitaxial growth goes hand in hand because it is difficult to locate an exact flake on a substrate that you want to measure. But I've seen some papers where people manage to locate mechanically exfoliated monolayer flakes of 2D materials (e.g. graphene) on SiO2 substrates. How are people doing this? In one of the papers that I read, they said they used a "telescope" to locate the flake (E. Stolyarova et al. PNAS 104 (22) 9209-9212 (2007)). Do anyone know what type of telescope this is?
Capacitance-based navigation is another technique people use to locate micrometer size sample. ( REVIEW OF SCIENTIFIC INSTRUMENTS 82, 073701 (2011) )
There are several ways to avoid epitaxial growth and study exfoliated flakes by STM. First you may prepare exfoliated flakes with large surface coverage, so they are easy to locate as done e.g in
- Scientific Reports 5, Article number: 14714 (2015) and Scientific Reports 6, Article number: 29726 (2016)
- Review of Scientific Instruments 88 (7), 076104 (2017) and 2D Materials 4 (4), 041005 (2017)
Or you may make some sort of markers that you can use to guide to the flakes e.g by EBL as done in Nano Lett., 2018, 18 (11), pp 6696–6702.
If you have big enough flakes and good enough optics approaching directly on the flake could work as well.
I hope these papers will help:
https://www.sciencedirect.com/science/article/pii/S0008622316303402
http://iopscience.iop.org/article/10.1088/2053-1583/aadd20/meta
https://dqmp.unige.ch/renner/wp-content/uploads/2018/05/heterostructure_preprint_submitted2018.pdf
It would be easy to track your sample if you can pre pattern your substrate using methods like Photolithography. Then by using an optical microscope which is connected to see the tip-sample junction of STM, we can see the grids/patterns made in the substrate and thus the flake of interest.
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