Novel 2D germanene dioxide monolayers. Mechanical properties, hole-mobility values, and carrier mobility

Using first-principles calculations, 2D germanene dioxide monolayers of freestanding and well-ordered GeO 4 tetrahedrons (4-GD) and GeO 6 tetrahedrons (6-GD) building blocks are found to be stable. 4-GD is formed by corner-sharing GeO 4 tetrahedrons in a rectangular network, and 6-GD consists of edge-sharing GeO 6 octahedrons. However, the insulating 6-GD is the strongest germanene dioxide monolayer with an energy difference of -4.93 eV, and can therefore play the role of a supporting substrate for nanostructures in sensing and catalytic applications. The bandgap of 4-GD monolayers is 2.8 eV, and 6-GD has slightly larger bandgaps of about 3.5 eV regardless of the chirality and width. It is found that both the imaginary part of the dielectric function and the absorption spectrum exhibit a consistent bandgap with the electronic structure diagram, suggesting the possibility of its use as an optical detector for ultraviolet light. Carrier mobility can be observed along the x and y directions; a maximum of 1.20 x 10⁴ cm² V^-1 s^-1 is observed. Their thermal stability can be confirmed by molecular dynamics at 300 and 500 K, suggesting that the novel 2D structures have a stable existence. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)