Kinetically Controlled Site-Specific Substitutions in Higher-Order Heterostructures

Targeted substitutions in extended solids have been historically challenging, limited by high temperature and the synthetic routes traditionally used. Here, we report the synthesis of new compounds in the (Pb x Sn 1– x Se) 1+δ TiSe 2 intergrowth family from designed amorphous precursors. By controlling local composition and using low reaction temperatures, the metastable quaternary compounds can be synthesized over the entire range of 0 ≤ x ≤ 1 as crystallographically aligned thin films. X-ray diffraction and electron microscopy confirm the formation of a solid solution in the Pb x Sn 1– x Se layer, with the overall and constituent structure both changing as a function of composition as predicted by Vegard’s law. Charge transfer between constituents and subsequent conduction in the TiSe 2 describes the observed transport properties. The mobility of the charge carriers is increased in compounds with the alloyed Pb x Sn 1– x Se layer, providing direct evidence that charge transport occurs predominantly in the dichalcogenide layer.