Supertetrahedral Layers Based on GaAs or InAs

Abstract

The solid-state compounds M 15 Tr 22As32 and M 3Ga6As8 (M = Sr, Eu; Tr = Ga, In) were synthesized by heating the elements, and their crystal structures were determined by single-crystal and powder X-ray diffraction (space group C2/c). The structures are hierarchical variants of the HgI2 type and consist of layers of polymeric T5 (M 15 Tr 22As32) or T6 supertetrahedra (M 3Ga6As8), separated by strontium or europium cations. These compounds constitute hitherto unknown GaAs- or InAs-based supertetrahedral structures and represent the first binary vacancy-free T5 and T6 supertetrahedra. Vacancies or mixed-metal strategies for charge compensation, as known from related chalcogenides, are not required for supertetrahedra based on charge-neutral GaAs or InAs. Optical band gap, resistivity, and Hall-effect measurements together with DFT calculations reveal that the supertetrahedral compounds are direct band gap semiconductors similar to binary GaAs or InAs. Magnetic susceptibility measurements confirm Eu2+ in Eu15Ga22As32, Eu15In22As32, and Eu3Ga6As8 and indicate antiferromagnetic ordering below 10 K.

III–V Clathrate Semiconductors with Outstanding Hole Mobility: Cs8In27Sb19 and A8Ga27Sb19 (A = Cs, Rb)

“…This is dissimilar to other reports of p-type ternary compounds containing III−V fragments, such as in the supertetrahedral layered compounds Ae 15 Tr 22 As 32 and Ae 3 Ga 6 As 8 (Ae = Sr, Eu; Tr = Ga, In), in which there is a substantial decrease in mobility down to 0.2− 98 cm 2 •V −1 •s −1 going from the binary to ternary compounds. 89 High hole mobility within bulk samples at room temperature is uncommon but can still be found in some compounds, such as doped CsBi 4 Te 6 (700−1000 cm 90−92 The ordered nature of the In−Sb framework may be a key to the high mobility of Cs 8 In 27 Sb 19 . It was shown that defects may significantly affect the electronic and optical properties of III− V semiconductors.…”

Polymorphism of Ba2SiP4

“…[10] and Na 23 Si 9n+19 P 12n+33 with n = 0-3. [11] To the best of our knowledge this uncommon condensation mode was sparely observed only in KSi 2 P 3 , [7] B 2 S 3 , [12] Li 9 B 19 S 33 , [13] M 15 Tr 22 As 32 and M 3 Ga 6 As 8 (M = Sr, Eu; Tr = Ga, In) [14] and a few other mixedmetal T3 chalcogenides. [15] The possibility of the formation of homonuclear phosphorus bonding distinguishes the family of phosphidosilicates from the oxido-and nitridosilicates.…”

“…[7] In contrast, the introduction of small and weak electronegative metals yields threedimensional structures of vertex-shared tetrahedra [8] or supertetrahedra with sizes ranged from T2 to T5 [9] and the feature of supertetrahedral fusion in Li 2 SiP 2 , LiSi 2 P 3[10] and Na 23 Si 9n+19 P 12n+33 with n = 0-3. [11] To the best of our knowledge this uncommon condensation mode was sparely observed only in KSi 2 P 3 , [7] B 2 S 3 , [12] Li 9 B 19 S 33 , [13] M 15 Tr 22 As 32 and M 3 Ga 6 As 8 (M = Sr, Eu; Tr = Ga, In) [14] and a few other mixedmetal T3 chalcogenides. [15] The possibility of the formation of homonuclear phosphorus bonding distinguishes the family of phosphidosilicates from the oxido-and nitridosilicates.…”

The Phosphidosilicates SrSi7P10and BaSi7P10

“…The basic building units of these compounds are SiP 4 tetrahedra condensed by vertices to T2 supertetrahedra (Figure 2, yellow) according to the Yaghi [ 20 ] notation. By zigzag fusion of these entities, which was sparely observed in related compounds, [ 6,10–11,21–28 ] chains are formed, depicted in turquoise in Figure 2. Further vertex‐edge condensation of these fused T2‐chain motifs – to the best of our knowledge only once observed [ 29 ] – yields in T2 layers, which are propagating in the ab plane, visualized by condensation of the blue T2 chains in Figure 2.…”