Synthesis and stability of two-dimensional Ge/Sn graphane alloys

There has been considerable interest in the germanium and tin graphane analogues due to their potential as optoelectronic building blocks, and novel topological materials. Here, we have synthesized for the first time alloyed germanium/tin graphane analogues from the topochemical deintercalation of CaGe_2-2xSn_2x (x = 0-0.09) in aqueous HCl. In these two-dimensional alloys, the germanium atom is terminated with hydrogen while tin is terminated with hydroxide. With greater tin incorporation, the band gap systematically shifts from 1.59 eV in GeH down to 1.38 eV for Ge_0.91Sn_0.09H_0.91(OH)_0.09, which allows for more sensitive photodetection at lower energies. In contrast to germanane's oxidation resistance, the Ge and Sn atoms in these graphane alloys rapidly oxidize upon exposure to air. This work demonstrates the possibility of creating functional tin-incorporated group IV graphane analogues.