Nanodevices from and electronic transport properties of Zr I2 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 ZrI2 to explore various structures and assess the feasibility of obtaining monolayer phases through mechanical exfoliation. Four stable phases of bulk ZrI2, namely the α(α′)-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 ZrI2 monolayers are systematically investigated, and conceptual nanodevices based on ml-α- and ml-hex-ZrI2 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-α-ZrI2 demonstrate a remarkable negative differential conductance effect. These findings illuminate the multifunctional nature of ZrI2 monolayers and highlight their potential applications in nanoelectronic devices.