Synthesis of Ti4Au3C3 and its derivative trilayer goldene through chemical exfoliation

Achieving large two-dimensional (2D) sheets of any metal is challenging due to their tendency to coalescence or cluster into 3D shapes. Recently, single-atom-thick gold sheets, termed goldene, was reported ¹ . Here, we raise the question if goldene can be extended to include multiple layers? The answer is yes , and trilayer goldene is the magic number, for reasons of electronegativity. Experiments are made to synthesize the atomically laminated phase Ti ₄ Au ₃ C ₃ through substitutional intercalation of Si layers in Ti ₄ SiC ₃ for Au. Density functional theory calculations suggest that it is energetically favorable to insert three layers of Au into Ti ₄ SiC ₃ , compared to inserting a monolayer, bilayer or more than three layers. Isolated trilayer goldene sheets, ~ 100 nm wide and 6.7 Å thick, were obtained by chemically etching the Ti ₄ C ₃ layers from Ti ₄ Au ₃ C ₃ nanolaminate templates. Furthermore, trilayer goldene is found in both hcp and fcc forms, where the hcp is ~ 50 meV/atom more stable at room temperature from ab initio molecular dynamics simulations.