Quantum confinement induced band gaps in MgB sub(2) nanosheets

The discovery of two-dimensional semiconducting materials, a decade ago, spawned an entire sub-field within solid-state physics that is focused on the development of nanoelectronics. Here we present a new class of semiconducting two-dimensional material based on hexagonal MgB sub(2). Although MgB sub(2) is a semimetal, similar to the other well-studied transition metal diborides, we demonstrate that, unlike the transition metal diborides, thinning MgB sub(2), to create nanosheets, opens a band gap in the density of states. We predict that a 7 A thick MgB sub(2) nanosheet will have a band gap of 0.51 eV. MgB sub(2) nanosheets differ from other two-dimensional semiconductors in that the band gap is introduced by (001) surfaces and is opened by the quantum confinement effect. The implications of these findings are that nanostructured MgB sub(2) is not merely a new composition, but also has intrinsic mechanisms for tuning its electronic properties, which may facilitate the development of nanoelectronics.