Stabilizing the Metastable: Controlled Chemical Vapor Deposition Growth of Monolayer 1T’ MoS₂

Transition metal dichalcogenides (TMDs) have emerged as a versatile platform for studying low-dimensional physics, as their properties are highly tunable via composition and crystal structure. In contrast to the well-studied semiconducting 2H phase, the metastable 1T′ phase, particularly MoS₂, is a promising material for next generation electronic, spintronic, and superconducting devices featuring Weyl semimetallicity, the quantum spin Hall effect, and superconductivity. However, the scalable synthesis of pure phase monolayers is hindered by thermodynamic instability. Here, we report a scalable bottom-up chemical vapor deposition (CVD) method for the direct synthesis of 1T’ MoS₂ monolayers. Layer number and coverage are studied by atomic force microscopy (AFM). The Fast Fourier Transform (FFT) analysis of the high resolution transmission electron microscopy (HRTEM) images reveals the characteristic superlattice of the 1T’ phase. X-ray photoelectron spectroscopy (XPS) further confirms the 1T′ phase via characteristic Mo 3d binding energies. Raman spectroscopy reveals the vibrational fingerprint of 1T’ MoS2 (J₁, J₃, and A_1g modes), in the absence of 2H phase modes. Temperature-dependent phonon behavior was analyzed. Both lattice thermal expansion and anharmonic effects contribute to the observed redshift of the vibrational frequencies with increasing temperature. This synthetic approach provides a pathway for fabricating other metastable TMDs, enabling the exploration of their unique electronic properties.