Conversion of 1D Nb₂Se₉ Nanowires to 2D Conductive NbSe₂ via Hydrogen Annealing: Structural and Electrical Characterization

Van der Waals (vdW) materials, consisting of multiple layers held together by weak vdW forces, have garnered significant interest due to their tunable electronic, optical, and mechanical properties. In this study, a one-dimensional (1D) Nb₂Se₉ nanowire template, known for its p-type semiconductor characteristics, was synthesized and converted into a conductive NbSe₂ nanowire through hydrogen annealing. The conversion process, performed at 300 and 500 °C, maintained the wire morphology and passed through an intermediate NbSe₃ phase. Structural analysis confirmed the conversion, showing preferred orientation growth in the vdWs direction [002]. Raman and X-ray diffraction results indicated that residual Se in the material increased interlayer distances and caused stress in the out-of-plane direction. Electrical measurements demonstrated that the converted NbSe₂ exhibited metallic properties with linear I-V curves and ohmic contact. The NbSe₂ nanowires converted at 300 °C exhibited superior performance, with a breakdown current density of 2.01 MA cm^-2, surpassing conventional nano metallic wire materials like Si, Cu, and SnO₂. This study highlights the potential of NbSe₂ nanowires for applications in nano devices, leveraging their high electrical conductivity and structural integrity maintained at low process temperatures suitable for back-end-of-line (BEOL) processes.