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Exfoliated Monolayer GeI2: Theoretical Prediction of a Wide-Band Gap Semiconductor with Tunable Half-Metallic Ferromagnetism

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journal contribution
posted on 09.09.2018, 00:00 by Chun-Sheng Liu, Xiao-Le Yang, Jin Liu, Xiao-Juan Ye
Two-dimensional wide-band gap semiconductors are promising candidates for high-temperature/power/frequency devices. However, the number of these pristine materials with band gaps larger than 2.2 eV is relatively small. Expectedly, properly enhancing the electronegativity differences among the constituent atoms could increase the band gap. Using first-principles calculations, including spin–orbit coupling, we propose a GeI2 monolayer with an intrinsic band gap of 2.59 eV, suggesting that it is a potential wide-band gap semiconductor. Interestingly, the layered semiconducting GeI2 has first been synthesized in 1968. Its cleavage energy (0.16 J/m2) is only half that of the graphite, indicating that the exfoliation of layered GeI2 could be experimentally feasible. Besides the confirmed dynamic stability, monolayer GeI2 can remain thermally stable at 600 K, which is suitable for operation at high temperature. Distinct light absorption in the spectral range from 240 to 650 nm for monolayer GeI2 promises applications in optoelectronic devices working under blue and ultraviolet light. Remarkably, semihydrogenation on the surface of GeI2 induces a transition from nonmagnetic semiconductor to ferromagnetic half-metal. Therefore, the GeI2 monolayer possesses great potential in future optoelectronics and spintronics.