Selection of metal–tellurium (M–Te) alloy as Recyclable Controlled Te Precursors for Wafer‐Scale Synthesis of M _x Te _y Thin Films

Wafer-scale synthesis of metal telluride films has been hindered by the high volatility and limited reactivity of tellurium. To overcome this, we introduce a confined tellurization strategy utilizing in situ formed metal-tellurium (M-Te) alloys as controllable Te sources. Systematic investigation on appropriate metal species through cohesive energy calculations and experiments demonstrates that the cohesive energy of the source metal and metal-to-Te atomic ratio in the source bilayer are the key parameters dictating Te flux. Among many metals, Au-Te and Ag-Te alloys provide steady Te flux while preventing the delamination of M/Te bilayer (observed with Pt, Mo, Cu) after metal deposition on Te layer and the undesired co-evaporation of metal (observed with In, Zn) during Te supply for M_xTe_y synthesis. With the Au-Te alloy, atomically-smooth, single-crystalline 4-inch Si₂Te₃ thin films are produced, which are the largest reported to date. The film thickness can be modulated by adjusting the Au/Te ratio, verified by structural and spectroscopic characterization. The generality of this concept is verified by synthesizing other tellurides, including MoTe₂ and Cr₂Te₃. The M-Te alloy source is recyclable by replenishing Te on the alloy, establishing this methodology as a robust and versatile platform for producing a wide range of high-quality metal telluride films.