Stabilization of Metastable Polymorphs on Single Crystal Oxide Substrates via Substrate Induced Strain in 2D/3D TMD/TMO Heterostructures: A case of Epitaxial MoS₂ Thin-film by Pulsed Laser Deposited, Role of Surface Chemistry and Structure

Structural polymorphs of two-dimensional 2D layered Van der Waal solids like MoS₂ hold great potential for major applications in the advanced electronics and energy sectors. Here, we have grown MoS₂ thin-film on different single crystal metal oxide substrates (SrLaAlO₄, c-Al₂O₃, SrTiO₃, LaAlO₃) by Pulsed Laser Deposition (PLD). We observe that on the structurally compatible tetragonal SrLaAlO₄ (001) substrate mixed 1T´+2H phase MoS₂ grows with a dominant (~75%) 1T´ phase, while on hexagonal c-Al₂O₃ (0001) substrate pure 2H phase grows, whereas 1T´ phase contribution varies in order SLAO>STO>LAO. Further, the chemical role of Sr is elucidated in the early growth on SLAO and STO. XRD, Raman spectroscopy, XPS, VBS, and EFM are used to analyse the properties of these films and phases.The pivotal role of lattice strain in stabilizing the initial layer(s) on SLAO has also observed. The mixed 1T´+2H phase in ultrathin film shows high room temperature resistivity (~2 mΩ cm) with respect to that of pure 2H phase (~14 mΩ cm). This substrate selective polymorphism with distinct electronic features provides an approach to stabilization of metastable phases of even soft Van der Waal solids on hard substrates for integration into novel device functions.