The Unique Electronic Structure of Mg₂Si: Shaping the Conduction Bands of Semiconductors with Multicenter Bonding

Abstract

The electronic structures of the antifluorite-type compound Mg Si is described in which a sublattice of short cation-cation contacts creates a very low conduction band minimum. Since Mg Si shows n-type conductivity without intentional carrier doping, the present result indicates that the cage defined by the cations plays critical roles in carrier transport similar to those of inorganic electrides, such as 12 CaO⋅7 Al O :e and Ca N. A distinct difference in the location of conduction band minimum between Mg Si and the isostructural phase Na S is explained in terms of factors such as the differing interaction strengths of the Si/S 3s orbitals with the cation levels, with the more core-like character of the S 3s leading to a relatively low conduction band energy at the Γ point. Based on these results and previous research on electrides, approaches can be devised to control the energy levels of cation sublattices in semiconductors.

Hybrid-Functional and Quasi-Particle Calculations of Band Structures of Mg2Si, Mg2Ge, and Mg2Sn

“…Similarly, our recent work revealed Sb-induced microstructure inhomogeneities in Mg2(Si,Sn) alloys [36]. [12,21,35], owing to a unique ntype electronic structure [45,46]. The experimental band gaps of Mg2Si, Mg2Ge, and Mg2Sn are known to be 0.77, 0.74, and 0.36 eV, respectively [1] [47-50].…”

“…For Mg2Si and Mg2Ge, the conduction band minimum (CBM) state (X1) does not belong to Mg or Si atoms, while the valence band maximum states are localized near atomic sites. Instead, the X1 state is localized near the interstitial site [45]. Under the tensile strain on Mg2Si and Mg2Ge, this CBM state ascends, while the next CBM state (X3), composed of Mg s states, descends, resulting in the band convergence between X1 and X3 [46].…”

“…The experimental band gaps of Mg2Si, Mg2Ge, and Mg2Sn are known to be 0.77, 0.74, and 0.36 eV, respectively [1] [47-50]. The valence and conduction band edge states are located at Γ and X points, respectively [45][46][47]. For Mg2Si and Mg2Ge, the conduction band minimum (CBM) state (X1) does not belong to Mg or Si atoms, while the valence band maximum states are localized near atomic sites.…”

Discovery of Hidden Classes of Layered Electrides by Extensive High-Throughput Material Screening

“…Despite many endeavors since the first crystalline electride grown three decades ago, 3 only a few electrides have been synthesized. [4][5][6][7][8][9][10][11][12][13] The first room-temperature stable inorganic electride was reported in 2003 by removing oxygen ions from the crystallographic cages of 12CaO.7Al 2 O 3 , yielding [Ca 24 Al 28 O 64 ] 4+ (4e -). 5 The high density of anionic electrons with loosely bounded nature makes [Ca 24 Al 28 O 64 ] 4+ (4e -) promising for a plethora of applications, such as efficient thermionic emitters, 14 electroninjection electrode for organic light-emitting diodes, 15,16 and high performance catalysts.…”

Fatigue Study of the Pre-Corroded 6082-T6 Aluminum Alloy in Saline Atmosphere

“…6061 aluminum alloys have %Mg + %Si (wt) in amounts greater than 1.4%, which favors the increase in mechanical resistance after heat treatment compared with other alloys such as 6063. Magnesium and silicon form Mg 2 Si compound, which behaves like a semiconductor [2,3]. Additionally, it contains amounts of Cu around 0.25% to improve corrosion resistance and 0.7% Fe, which results in the precipitation of the ternary compounds Al x Fe y Si z [4,5].…”