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SrSn crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Sr is bonded in a 5-coordinate geometry to seven equivalent Sn atoms. There are five shorter (3.48 Å) and two longer (3.67 Å) Sr–Sn bond lengths. Sn is bonded in a 9-coordinate geometry to seven equivalent Sr and two equivalent Sn atoms. Both Sn–Sn bond lengths are 2.99 Å.
SrSn(BO3)2 is Calcite-derived structured and crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Sr2+ is bonded to six equivalent O2- atoms to form SrO6 octahedra that share corners with six equivalent SnO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Sr–O bond lengths are 2.56 Å. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. Sn4+ is bonded to six equivalent O2- atoms to form SnO6 octahedra that share corners with six equivalent SrO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Sn–O bond lengths are 2.09 Å. O2- is bonded in a distorted trigonal planar geometry to one Sr2+, one B3+, and one Sn4+ atom.
SrSn(PO4)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Sr2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.61–2.99 Å. Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six equivalent PO4 tetrahedra. There are a spread of Sn–O bond distances ranging from 2.03–2.10 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three equivalent SnO6 octahedra. The corner-sharing octahedra tilt angles range from 41–50°. There are a spread of P–O bond distances ranging from 1.52–1.58 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Sr2+ and one P5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Sr2+, one Sn4+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Sr2+, one Sn4+, and one P5+ atom.
Abstract Germanium-based oxides such as rutile GeO 2 are garnering attention owing to their wide band gaps and the prospects of ambipolar doping for application in high-power devices. Here, we present the use of germanium tetraisopropoxide (GTIP), a metal-organic chemical precursor, as a source of germanium for the demonstration of hybrid molecular beam epitaxy for germanium-containing compounds. We use Sn 1- x Ge x O 2 and SrSn 1- x Ge x O 3 as model systems to demonstrate our synthesis method. A combination of high-resolution X-ray diffraction, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy confirms the successful growth of epitaxial rutile Sn 1- x Ge x O 2 on TiO 2 (001) substrates up to x = 0.54 and coherent perovskite SrSn 1- x Ge x O 3 on GdScO 3 (110) substrates up to x = 0.16. Characterization and first-principles calculations corroborate that germanium occupies the tin site, as opposed to the strontium site. These findings confirm the viability of the GTIP precursor for the growth of germanium-containing oxides by hybrid molecular beam epitaxy, thus providing a promising route to high-quality perovskite germanate films.