Phase Engineering of a 1D van der Waals Thin Film

Phase engineering has been extensively explored in 2D van der Waals (vdW) materials, especially in transition-metal dichalcogenides, whereas less focus has been given to phase transitions in lower-dimensional systems. In this study, a transformative phase transition phenomenon in 1D vdW materials is reported, for the first time, with a focus on niobium tetra-telluride (NbTe₄). Through precise compositional control during sputtering deposition followed by strategic thermal annealing, the phase stability is elucidated between the amorphous, monoclinic, and tetragonal phases in NbTe₄ thin films. It is found that the monoclinic-to-tetragonal phase transition exhibited a pronounced insulator–metal transition behavior, accompanied by a significant change in resistance. High-resolution transmission electron microscopy revealed atomic-scale structural modifications, shedding light on the underlying mechanisms propelling this phase transition. Notably, the reversibility of this phase transition is demonstrated under electrical pulses, underscoring the potential of 1D vdW materials across a range of applications, from electronics to optoelectronics.