Quantum confinement induced band gaps in MgB ₂ nanosheets

Abstract

The discovery of two-dimensional semiconducting materials, a decade ago, spawned an entire subfield 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 2 . Although MgB 2 is a semimetal, similar to the other well-studied transition metal diborides, we demonstrate that, unlike the transition metal diborides, thinning MgB 2 , to create nanosheets, opens a band gap in the density of states. We predict that a 7 Å thick MgB 2 nanosheet will have a band gap of 0.51 eV. MgB 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 2 is not merely a new composition, but also has intrinsic mechanisms for tuning its electronic properties, which may facilitate the development of nanoelectronics.

Simple, Green, and High‐Yield Production of Boron‐Based Nanostructures with Diverse Morphologies by Dissolution and Recrystallization of Layered Magnesium Diboride Crystals in Water

“…Further experimental investigations are required to understand the effect of the dissolution aide being used on the morphology of boron‐based nanostructures. Due to the presence of functionalized boron, these nanostructures exhibit properties that are distinct from those of parent MgB 2 . To obtain nanostructures that are chemically identical to parent MgB 2 it would be promising to explore its exfoliation in the presence of organic solvents .…”

“…Due to the presence of functionalized boron, these nanostructures exhibit properties that are distinct from those of parent MgB 2 . [82] To obtain nanostructures that are chemically identical to parent MgB 2 it would be promising to explore its exfoliation in the presence of organic solvents. [83] Green et al recently demonstrated the possibility of obtaining pristinen anosheetsb ye xfoliating layered metal diborides in organic solvents.…”

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

“…The former confines the carriers effective mass ( m ∗) in nanosheets, while the latter determines the electron‐spin interaction at the interface. [ 22–25 ] And thus the band structure in 2D materials, corresponding to the optical and transfer behavior of DOFs, are modulated. [ 26–29 ] By constructing polarized heterostructures with ultraclean interfaces, various proximity effects and devices have been demonstrated, where the polarization penetrates into the neighboring nonpolarized layer.…”

High-temperature phonon-mediated superconductivity in monolayer Mg2B4C2

“…The discovery of highly crystalline two-dimensional (2D) superconductors [1][2][3][4][5], such as NbSe 2 monolayer [6][7][8][9], has provided new possibilities for van der Waals (vdW) heterostructures nano-engineering of novel insulator-superconductor interfaces [10] and 2D Josephson junctions, without the need of an insulating layer [11]. One main challenging issue in the realization of 2D superconductivity is that most of the well-known conventional bulk superconductors either do not superconduct or poorly superconduct when their dimensions are reduced [6][7][8][12][13][14][15][16][17]. Although numerous 2D phononmediated superconductors have recently been predicted from first-principles calculations, the highest predicted intrinsic T c stayed around 20 K [17][18][19][20][21][22][23][24] (19 K for B 2 C monolayer [21], 10.3 K for B 2 O monolayer [17], and 19-25 K for borophenes [22], to name a few).…”

“…Despite the large success with the bulk conventional superconductors, two-dimensional intrinsic superconductors having a high-T c remained elusive. Notably, various attempts have been made to realize superconductivity in the 2D analogues of bulk MgB 2 [13,32,51,[69][70][71][72][73][74]. On the one hand, Xu and Beckman proposed a quasi-2D MgB 2 nanosheet with inert surfaces, which turns out to be a semiconductor with a bandgap of 0.51 eV resulting from the quantum confinement effects [13].…”