Monolayer tantalum disulfide epitaxially grown on Au(111) is studied in real time during molecular beam epitaxy using low-energy electron microscopy and microdiffraction. Complementary x-ray photoelectron emission microscopy provides insight into the chemical and electronic structure of the grown layers. Our study reveals a previously unreported growth mechanism where the formation of $2\mathrm{H}\text{−}{\mathrm{TaS}}_2$ proceeds via a transient $1\mathrm{T}\text{−}{\mathrm{TaS}}_2$ phase. The $1\mathrm{T}\text{−}{\mathrm{TaS}}_2$ phase exhibits a significantly higher growth rate than the $2\mathrm{H}\text{−}{\mathrm{TaS}}_2$ phase, with growth proceeding mainly in the 1T phase. By comparison with ${\mathrm{TaSe}}_2$ on Au(111), we find that this growth mechanism is common to other Ta-based transition-metal dichalcogenides on Au(111). Furthermore, we find spectroscopic evidence for the presence of charge-density-wave order in $1\mathrm{T}\text{−}{\mathrm{TaS}}_2$ on Au(111). These findings provide perspectives on the growth dynamics and phase control of ${\mathrm{TaS}}_2$, opening up avenues for tailoring its electronic properties through substrate interaction and phase engineering.

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• 2-dimensional systems
• Transition metal trichalcogenides
• Low-energy electron diffraction
• Low-energy electron microscopy
• X-ray photoelectron spectroscopy