Polygermanosilyne calcium hydroxide intercalation compounds formed by topotactic transformation of Ca(Si1-xGex)(2) alloy zintl phases in ambient atmosphere

Epitaxial thin films of Ca(Si1-xGex)(2) with 0 < x less than or equal to 1 are found to react with the moisture of ambient atmosphere to form new Ca-S i-Ge-O-H compounds which were studied by X-ray diffraction, energy dispersi ve X-ray analysis, infrared absorption, and thermally induced hydrogen deso rption measurements. Pure CaGe2 forms the polygermyne calcium hydroxide int ercalation compound Ca(OH)(2)(GeH)(2) upon exposure to humidity, with a tri gonal tr6 crystal lattice with a = 4.00(1) and c = 65.3(1) Angstrom. In mix ed Ca(Si1-xGex)(2) with smaller Ge content, the group-14 layers are subject to intense oxidation leading to decreased crystallinity. The products exhi bit characteristic colours and intense photoluminescence, the peak luminesc ence varying from 1.35 eV for the reaction product of Ca(Si0.3Ge0.7)(2) to 2.6 eV for that of Ca(Si0.5Ge0.5)(2).