Structural, electronic and optical characteristics of SrGe2 and BaGe2: A combined experimental and computational study

Pressure-induced stable structures and physical properties of Sr–Ge system

“…[1,2] For example, an excellent ZT value = 1.1 was achieved in the n-type Mg 2 (Si, Sn) system under ambient condition, and they can be seen as promising thermoelectric materials. [3] Both BaGe 2 and SrGe 2 show high optical absorption coefficients (7.5×10 4 cm −1 and 7.8×10 4 cm −1 at hω = 1.5 eV), indicating that they are ideal solar cell candidates. [4] Pressure has become a useful tool to expand the variety of materials, and modify accessible structure patterns with excellent properties.…”

“…[3] Both BaGe 2 and SrGe 2 show high optical absorption coefficients (7.5×10 4 cm −1 and 7.8×10 4 cm −1 at hω = 1.5 eV), indicating that they are ideal solar cell candidates. [4] Pressure has become a useful tool to expand the variety of materials, and modify accessible structure patterns with excellent properties. In recent years, novel stoichiometries with superconductivity were studied in compounds constituted by metals and group IV elements associated with the wellknown effect of pressure.…”

“…As is well known, some compositions (such as Sr 2 Ge, SrGe 2−δ , SrGe 2 , SrGe 3 , SrGe 6−δ ) of Sr-Ge have been studied and synthesized under pressure and show excellent properties. [4,[14][15][16][17][18] For instance, I4/mmm SrGe 3 phase was synthesized at 13 GPa and 1100 • C. [14] It showed superconductivity with T c = 6.0 K. SrGe 2−δ was obtained at 2 GPa and 900 • C, which is a superconductor with T c about 7.3 K. [15] Furthermore, Pnma SrGe 2 , a semiconductor with good optical property, was synthesized by the Ar arc-melting technique. [4] However, some problems remain to be further solved: (i) whether the new Sr-Ge compounds are stable at moderate conditions; (ii) the ground-state structures and properties of Sr-Ge system under high pressure; and (iii) the unit of germanium in the Sr-Ge compounds.…”

Fabrication of SrGe2 thin films on Ge (100), (110), and (111) substrates

“…Alkaline-earth silicides have been widely investigated because of their useful functions for many technological applications such as solar cells [ 1 – 3 ], thermoelectrics [ 4 – 6 ], and optoelectronics [ 7 – 9 ]. However, the study of germanides has not been active compared to that of silicides even though some studies have predicted interesting electrical and optical properties for germanides [ 10 – 16 ].…”

“…SrGe 2 is one of the alkaline-earth germanides. Theoretical and experimental studies of bulk SrGe 2 have revealed the following properties [ 12 – 16 ]: (i) a BaSi 2 -type structure (orthorhombic, space group: , no. 62, Z = 8), (ii) an indirect transition semiconductor with a band gap of approximately 0.82 eV, and (iii) an absorption coefficient of 7.8 × 10 5 cm −1 at 1.5 eV photon, which is higher than that of Ge (4.5 × 10 5 cm −1 at 1.5 eV photon).…”