Nanodevices from and electronic transport properties of ZrI2 monolayers

Two-dimensional transition-metal dihalides possess immense potential for applications in low-dimensional nanodevices because of their exceptional thermal and chemical stabilities, unique mechanical and electronic properties, and ultrahigh carrier mobility. In this study, an extensive structural search utilizing first-principles total-energy calculations combined with the particle-swarm optimization algorithm is conducted on bulk ${\mathrm{Zr}\mathrm{I}}_{2}$ to explore various structures and assess the feasibility of obtaining monolayer phases through mechanical exfoliation. Four stable phases of bulk ${\mathrm{Zr}\mathrm{I}}_{2}$, namely the \ensuremath{\alpha}(\ensuremath{\alpha}\ensuremath{'})-phase, hex-phase, and tet-phase, along with their corresponding monolayers, are successfully obtained. All bulk and monolayer phases exhibit dynamic and mechanical stability. The mechanical, electronic transport, and photoelectric properties of the ${\mathrm{Zr}\mathrm{I}}_{2}$ monolayers are systematically investigated, and conceptual nanodevices based on ml-\ensuremath{\alpha}- and ml-hex-${\mathrm{Zr}\mathrm{I}}_{2}$ monolayers are constructed. These nanodevices show remarkable transport characteristics, including excellent rectifying effects, low threshold voltages, high current densities, outstanding field-effect behaviors, and sensitive photoelectric responses. Moreover, p-n junction diodes constructed using ml-\ensuremath{\alpha}-${\mathrm{Zr}\mathrm{I}}_{2}$ demonstrate a remarkable negative differential conductance effect. These findings illuminate the multifunctional nature of ${\mathrm{Zr}\mathrm{I}}_{2}$ monolayers and highlight their potential applications in nanoelectronic devices.