Tunneling Effects in Crossed Ta₂Pt₃Se₈-Ta₂Pd₃Se₈Nanowire Junctions: Implications for Anisotropic Photodetectors

Quasi-one-dimensional van der Waals (vdW) materials are a promising system for future applications in electronics and optoelectronics. Here we report systematic studies on the electronic and optoelectronic properties of crossed junctions composed of two vdW nanowires: p-type Ta2Pt3Se8 (TPtS) and n-type Ta2Pd3Se8 (TPdS). Asymmetric nonlinear output behaviors are observed in crossed junctions, where a rectifying barrier is formed because of depletion of the majority carriers at the heterointerface with a transmission probability of ∼0.025. Optoelectronic characteristics reveal inelastic tunneling effects of the crossed junctions. Furthermore, polarized photocurrent measurements demonstrate that isotropic photocurrent signals are detected at the TPtS-TPdS interface, while the maximum photocurrent signals for each nanowire are present when incident light is polarized along the nanowire direction. This indicates that photoexcited carriers in both TPtS and TPdS nanowires can tunnel through the rectifying barrier at the crossed junction to generate photocurrent signals. Additionally, our photocurrent spectral measurements find that the band gaps of individual nanowires are thickness-dependent and range from 0.9 to 1.1 eV, in good agreement with theoretical predictions. These results shed light on the electrical transport and photocurrent generation mechanisms for the nanoscale crossed junctions, opening up new avenues for engineering future vdW-material-based electronic and optoelectronic devices, such as anisotropic photodetectors and multiterminal circuits.