Crystal Structure of β-Ga2O3

Abstract

The crystal structure of β-Ga2O3 has been determined from single-crystal three-dimensional x-ray diffraction data. The monoclinic crystal has cell dimensions a=12.23±0.02, b=3.04±0.01, c=5.80±0.01 A and β=103.7±0.3° as originally reported by Kohn, Katz, and Broder [Am. Mineral. 42, 398 (1957)]. There are 4 Ga2O3 in the unit cell. The most probable space group to which the crystal belongs is C2h3—C2/m; the atoms are in five sets of special positions 4i: (000, ½½0)±(x0z). There are two kinds of coordination for Ga3+ ions in this structure, namely tetrahedral and octahedral. Average interionic distances are: tetrahedral Ga–O, 1.83 A; octahedral Ga–O, 2.00 A; tetrahedron edge O–O, 3.02 A; and octahedron edge O–O, 2.84 A. Because of the reduced coordination of half of the metal ions, the density of β-Ga2O3 is lower than that of α-Ga2O3 which has the α-corundum structure. Also the closest approach of two Ga3+ ions in β-Ga2O3 is 3.04 A which is considerably larger than the closest approach of metal ions in the sesquioxides with the α-corundum-type structure and, in agreement with the results of thermodynamic measurements, the β phase appears to be the structurally more stable one. The average Ga–O distances in the structure seem to account for the fact that although the Ga3+ ion is substantially larger than the Al3+ ion its quantitative preference for tetrahedrally coordinated sites when substituted for Fe3+ ion in the iron garnets is very nearly the same as that of the Al3+ ion. The structure accounts for a recent result obtained by Peter and Schawlow from paramagnetic-resonance measurements on Cr3+-ion-doped β-Ga2O3, namely that the Cr3+ ion substitutes for the Ga3+ ions in a single set of equivalent octahedral sites. The magnetic aspects of the β-Ga2O3 structure are discussed and it is shown that a possible Fe2O3 isomorph could be expected to be at least antiferromagnetic with a Néel temperature of about 700°K Furthermore, a knowledge of the β-Ga2O3 structure and of the nature of site preferences of the Ga3+ and Fe3+ ions in the garnets lead to a prediction regarding the structure of the ferrimagnetic crystals of formula Ga2—xFexO3 recently discovered by Remeika.

Nanostructures and thin films of transparent conductive oxides studied by perturbed angular correlations

“…A BaF 2 6-detector PAC setup was used [17], but when measuring single crystals only one 4-detector plane of this setup was selected, where the sample's c-axis was oriented within the detector plane at The lattice parameters of the Ga 2 O 3 powder samples and nanowires were previously found to be "relaxed" [18], i.e., with standard bulk parameters, thus the values a = 12.23Å, b = 3.08Å, c = 5.80Å and = 107.3 o , reported in ref. [10], were considered, which are in agreement with the optimum estimated atomic positions and lattice parameters found in the theoretical study of Ga 2 O 3 done by F. Litimein et al [19].…”

“…Thus, in this study, thin films of ZnO and Cd x Zn 1 x O (x = 0.16) were investigated. Gallium oxide (Ga 2 O 3 ) has the biggest band-gap among the transparent conductive oxides, 4.8 eV , making it interesting for photonics working in the UV and visible wavelength region [3,[10][11][12][13]. However, as in the case of ZnO, it is an intrinsic n-type semiconductor and it has been proven very difficult to obtain p-type doping, which is fundamental for technological applications.…”

“…In the case of Ga 2 O 3 , a 1 ⇥ 2 ⇥ 2 supercell of the -Ga 2 O3 crystalline structure was considered (80 atoms), using the lattice parameters reported in ref. [10]. Since the Ga atoms have two non-equivalent sites, octahedral and tetrahedral, two simulations were performed, considering the 111 Cd probe in each site.…”

Supported Ga-oxide Catalyst for Dehydrogenation of Ethane

“…However, the peak intensity of the low transition energy (10373 eV) is higher than that of the high transition energy (10378 eV) 28) . It is known that β-Ga2O3 is the only stable phase 29) and it includes two kinds of Ga, tetrahedral Ga and octahedral Ga, in its structure 30) . Thus, we calculated spectra of tetrahedral Ga and octahedral Ga shown in Fig.…”

Lanthanide-doped semiconductor nanocrystals: electronic structures and optical properties

“…[197,198]. The structure of β-Ga 2 O 3 is monoclinic with a space group of C 2/m , and Ga 3+ ions occupy two crystallographic sites, namely tetrahedral and octahedral, respectively [199]. (Fig.…”