Bonding and electronics of the MoTe2/Ge interface under strain

Understanding the interface formation of a conventional semiconductor with a monolayer of transition-metal dichalcogenides provides a necessary platform for the anticipated applications of dichalcogenides in electronics and optoelectronics. We report here, based on the density functional theory, that under in-plane tensile strain, a 2H semiconducting phase of the molybdenum ditelluride $({\mathrm{MoTe}}_{2})$ monolayer undergoes a semiconductor-to-metal transition and in this form bonds covalently to bilayers of Ge stacked in the [111] crystal direction. This gives rise to the stable bonding configuration of the ${\mathrm{MoTe}}_{2}$/Ge interface with the $\ifmmode\pm\else\textpm\fi{}\mathrm{K}$ valley metallic, electronic interface states exclusively of a Mo $4d$ character. The atomically sharp Mo layer represents therefore an electrically active (conductive) subsurface $\ensuremath{\delta}$-like two-dimensional profile that can exhibit a valley-Hall effect. Such system can develop into a key element of advanced semiconductor technology or a novel device concept.