Elementary processes governing VAlC chemical etching in HF.

The literature on MXenes, an important class of 2D materials discovered in 2011, is now abundant. Yet, the lack of well-defined structures, with definite crystal orientations, has so far hindered our capability to identify some key aspects ruling MXene's chemical exfoliation from their parent MAX phase. Herein the chemical exfoliation of VAlC is studied by using well-defined square pillars with lateral sizes from 7 μm up to 500 μm, processed from centimeter-sized VAlC single crystals.

Mechanical Exfoliation of Select MAX Phases and Mo Ce Al C Single Crystals to Produce MAXenes.

MXenes-2D carbides/nitrides derived from their bulk nanolamellar M AX phase (MAX) counterparts-are, for the most part, obtained by chemical etching. Despite the fact that the MA bonds in the MAX phases are not weak, in this work it is demonstrated that relatively large MAX single crystals can be mechanically exfoliated using the adhesive tape method to produce flakes whose thickness can be reduced down to half a unit cell. The exfoliated flakes, transferred onto SiO /Si substrates, are analyzed using electric force microscopy (EFM).