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We demonstrate that structural and spectroscopic information can be obtained on exfoliated nanocrystals as thin as 6 nm. This can be achieved by using a combination of micro X-ray fluorescence (μXRF), micro X-ray absorption near-edge spectroscopy (μXANES), and X-ray microdiffraction (μXRD) techniques. Highly focused, tunable X-ray beams available at synchrotron sources enable one to use these non-invasive characterization tools to study exfoliated samples on a variety of substrates. As an example, we focused on exfoliated nanocrystals of the high temperature superconductor Bi2Sr2CaCu2O8+δ. μXRF is used to locate the sample of desired thickness; μXANES and μXRD are used to obtain electronic and structural information, respectively. We find that the '4.7b' structural modulation, characteristic of the bulk crystals, is drastically suppressed for exfoliated crystals thinner than 60 nm. [ABSTRACT FROM AUTHOR]

In the recently discovered class of materials known as topological insulators, the presence of strong spin-orbit coupling causes certain topological invariants in the bulk to differ from their values in vacuum. The sudden change in invariants at the interface results in metallic, time reversal invariant surface states whose properties are useful for applications in spintronics and quantum computation. However, a key challenge is to fabricate these materials on the nanoscale appropriate for devices and probing the surface. To this end we have produced 2 nm thick nanocrystals of the topological insulator Bi2Se3 via mechanical exfoliation. For crystals thinner than 10 nm we observe the emergence of an additional mode in the Raman spectrum. The emergent mode intensity together with the other results presented here provide a recipe for production and thickness characterization of Bi2Se3 nanocrystals. [ABSTRACT FROM AUTHOR]