Exfoliation and Analysis of Large-area, Air-Sensitive Two-Dimensional Materials

Abstract

We describe methods for producing and analyzing large, thin flakes of air-sensitive two-dimensional materials. Thin flakes of layered or van der Waals crystals are produced using mechanical exfoliation, in which layers are peeled off a bulk crystal using adhesive tape. This method produces high-quality flakes, but they are often small and can be hard to find, particularly for materials with relatively high cleavage energies such as black phosphorus. By heating the substrate and the tape, two-dimensional material adhesion to the substrate is promoted, and the flake yield can be increased by up to a factor of ten. After exfoliation, it is necessary to image or otherwise analyze these flakes but some twodimensional materials are sensitive to oxygen or water and will degrade when exposed air. We have designed and tested a hermetic transfer cell to temporarily maintain the inert environment of a glovebox so that air-sensitive flakes can be imaged and analyzed with minimal degradation. The compact design of the transfer cell is such that optical analysis of sensitive materials can be performed outside of a glovebox without specialized equipment or modifications to existing equipment.

Visualizing the Effect of Oxidation on Magnetic Domain Behavior of Nanoscale Fe3GeTe2 for Applications in Spintronics

“…Bulk FGT crystals were exfoliated inside a nitrogen glovebox (H 2 O, O 2 < 0.5 ppm) . A 27 nm thick flake, which are measured using atomic force microscopy (AFM) (Supporting Information Figure S1), was selected and transferred onto a 50 nm thick SiN x membrane TEM window using a dry transfer method involving polydimethylsiloxane (PDMS) and polycarbonate (PC). The residual PC was removed by thermally annealing at 350 °C and a vacuum of 2 e – 2 mbar for 3 h, in a vacuum chamber connected to the glovebox .…”