Controlled Bipolar Doping of One-Dimensional Van der Waals Nb₂Pd₃Se₈

2D layered materials such as graphene, transition metal dichalcogenides (TMDCs), h-BN, and black phosphorous have been extensively studied in a wide range of applications due to their fascinating structural, physical, and chemical properties. However, as the width of the 2D semi-infinite plane becomes narrow to meet the stringent dimensional requirements of the transistor, the dangling bond density at the edge of 2D vdW increases, resulting in degradation of electronic performance. To solve such scale-down problems, research has been conducted in recent years on one-dimensional (1D) vdW materials with a further reduced dimension from a 2D structure. 1D vdW materials, where single molecular chains with strong covalent bonds are assembled by a weak vdW force, are free of broken or dangling bonds on the chain surface, even when separated by a diameter of less than 1 nm. On the basis of these structural features, various 1D vdW material-based applications have been demonstrated, such as molecular connectors, transistors, and sensors. In recent years, ternary 1D transition metal chalcogenides containing a noble metal such as Pd or Pt have gained attention as promising semiconducting materials for electronic and optoelectronic devices. For example, Nb₂Pd₃Se₈, successfully synthesized by Keszler et al. Nevertheless, research into the stable tuning of electrical properties, which is a prerequisite for basic electronic materials, is still in its infancy stage for 1D vdW materials.<br/>In this study, we introduce a new ternary transition metal chalcogenide, Nb₂Pd₃Se₈, which was successfully synthesized via chemical vapor transport (CVT) method using iodine as a transport agent. Furthermore, we first demonstrated the chemical doping of Nb₂Pd₃Se₈, which is a representative n-type 1D vdW material, through chemically doping AuCl₃ and β-nicotinamide adenine dinucleotide (NADH) as p-type and n-type dopants, respectively. The concentration of holes and electrons controlled by varying the immersion time in the doping solution were effectively confirmed by spectroscopic and transport studies. In addition, we demonstrated an axial p−n junction on Nb2Pd3Se8 that exhibits near-perfect rectifying behavior using a selective doping method. We believe that this work can promote research based on 1D vdW semiconductors for future electronic applications.