Novel Au- and Ge-based two-dimensional materials formed through topotactic transitions of AlB₂-like structures

Abstract

The topotactic reaction of a layered compound, for example CaGe2, with HCl solution is a common and facile method to produce two-dimensional (2D) materials. In this work we demonstrate with first-principles calculations that this technique can potentially lead to a whole new family of 2D materials starting from three-dimensional crystals with AlB2-like structures. As representative cases, we show here that the de-intercalation of Sc and Ca atoms from ScAuGe and Ca2AuGe3 crystals is strongly exothermic and produces the stable 2D monolayers AuGeH and AuGe3H3, respectively. Remarkably, both metals (AuGeH) and semiconductors (AuGe3H3) can be prepared by this method. Based on the broad availability of AlB2-like structures with varying stoichiometries, there are several possibilities to prepare novel functional 2D materials with suitable topotactic transitions.

Ca- and Sc-based ternary AlB2-like crystals: a first-principles study

“…This configuration is in agreement with experimental studies [45] [47] to be the same as that of Ca 2 AgSi 3 . In the recent DFT study [40], it was shown that the topotactic transformation of Ca 2 AuGe 3 can lead to the 2D material with composition AuGe 3 H 3 . With respect to electronic properties, both Ca 2 AgSi 3 and Ca 2 AuGe 3 are metallic.…”

“…In particular, when CaSi 2 (and likewise [37] for CaGe 2 ) crystals react with a solution of HCl acid [32], Ca atoms are removed and H atoms (or OH groups) are attached to the silicene layer to produce the wide-band gap semiconductor silicane (or siloxene). In a recent study [40], we showed with firstprinciples calculations that similar reactions (termed topotactic transitions or transformations) can be used to prepare Au-and Ge-based two-dimensional materials from the AlB 2 -like crystals of ScAuGe and Ca 2 AuGe 3 . In fact, the same approach can prepare a whole new family of 2D systems, a realization that serves as the main motivation to study the structural and electronic properties of the corresponding three-dimensional precursors.…”

Improving the magnetic moment of Ca2Ge and promoting the conversion of semiconductors to diluted magnetic semiconductors using Mn-doping

“…[4][5][6][7][8] Recently, investigations of DMS have mainly focused on III-V, IV, II-VI, oxide and sulde semiconductors, such as GaAs, GaN, Si, Ge, ZnO, MoS 2 , etc. [9][10][11][12][13] The preparation of DMS mainly uses transition metal atoms or rare earth ions, which have spin magnetic moment, doped to substitute some atoms in the semiconductor material. [14][15][16] The magnetic moment of DMS is produced by the exchange of p state electrons of the anions and d state electrons of the magnetic ions, which are changed by the external temperature and doping concentration, so they may be ferromagnetic, sub ferromagnetic and antimagnetic.…”

Effect of stress on electronic structure and optical properties of cubic Ca2Ge

“…Ca 2 Ge is a novel semiconductor material whose crystal structure and photoelectric properties are similar to Ca 2 Si [1,2]. With respect to Si, Ge has larger charge carrier mobility, a smaller dielectric constant and a larger excitation radius (Ge-24.3 nm, Si-4.9 nm), and hence a stronger quantum size effect [3,4]; Furthermore, Ca 2 Ge is compatible with the conventional Si processes and overcomes the physical quantum limitations of Si (conventional Si integrated circuit IC in the range * Author to whom any correspondence should be addressed.…”