Enhanced proximity effect near the submonolayer terrace of the high-$T_c$ superconductor Fe(Te,Se)

Interest in the superconducting proximity effect has been ignited for its crucial role in various superconducting quantum devices, together with the potential to construct topological superconductivity. In this work, monolayer Fe (Te, Se) as a high-critical temperature ($T_c$) superconductor is epitaxially grown on semiconducting $\mathrm{SrTi}{O}_3$ (STO) substrates with a nominal coverage less than 1, to generate coplanar heterostructures of monolayer Fe (Te, Se) and STO. A proximity-induced full superconducting gap is detected on STO with an intriguingly extended decay length when the boundary is formed by a Fe (Te, Se) submonolayer terrace. The $T_c$, gap anisotropy, and possible causes of such proximity-induced superconductivity are discussed in detail, which provides insights into the interfacial superconductivity in the heterostructure of a low-dimensional superconductor and a semiconductor, and might pave the way for fabricating better high-$T_c$ superconductor-semiconductor devices.