Structural, Electrical, and Optical Properties of the Tetragonal, Fluorite-Related Zn_0.456In_1.084Ge_0.460O₃

Abstract

We report the discovery of Zn 0.456 In 1.084 Ge 0.460 O 3 , a material closely related to bixbyite. In contrast, however, the oxygen atoms in this new phase occupy 4 Wyckoff positions, which result in 4 four-coordinate, 24 sixcoordinate (2 different Wyckoff positions), and 4 eight-coordinate sites as compared to the 32 six-coordinate (also 2 different Wyckoff positions) sites of bixbyite. This highly ordered material is related to fluorite, Ag 6 GeSO 8 , and γ-UO 3 and is n-type with a bulk carrier concentration of 4.772 × 10 14 cm −3 . The reduced form displays an average room temperature conductivity of 99(11) S· cm −1 and an average optical band gap of 2.88(1) eV. These properties are comparable to those of In 2 O 3 , which is the host material for the current leading transparent conducting oxides. The structure of Zn 0.456 In 1.084 Ge 0.460 O 3 is solved from a combined refinement of synchrotron X-ray powder diffraction and time-of-flight neutron powder diffraction and confirmed with electron diffraction. The solution is a new, layered, tetragonal structure in the I4 1 /amd space group with a = 7.033986(19) Å and c = 19.74961(8) Å. The complex cationic topological network adopted by Zn 0.456 In 1.084 Ge 0.460 O 3 offers the potential for future studies to further understand carrier generation in ∼3 eV oxide semiconductors.

A Detailed Study on the Structural, Electrical and Optical Properties of (ZnO-GeO2) Substituted In2O3 Transparent Conducting Oxide

“…The electrical conductivity of pellet samples for Zn0.1In1.8Ge0.1O3 composition is 308 S/cm and 1060 S/cm for unreduced and reduced samples respectively. The reduced conductivity of Zn0.476In1.032Ge0.476O3 decreased up to 135 S/cm [17,[20][21][22]. Conductivity results indicate that this new system has similar conductivity behavior of other In2O3 based ternary system [21,22].…”

“…GeO2 bulk system or reaction with alumina crucible. However, Rickert et al[17] indexed that Zn0.456In1.084Ge0.460O3 (ZIGO) contained three phases and this new phase not related to bixbyite on the contrary it is fluorite related tetragonal phases.…”

Site Identity and Importance in Cosubstituted Bixbyite In2O3

“…Sample dimensions and masses were taken at each step to apply geometry and thickness corrections and the sheet resistance was converted to bulk conductivity [33]. Additionally, a porosity correction following the Bruggeman symmetric medium model was applied to each result, assuming that the air in the pellet acts as an insulating phase, following the same procedure as reported previously [13,34].…”

“…The constituent identities and their site preferences have been linked to crystal structure, however, as exhibited by the cosubstitution of Zn/Ge pairs. In this instance, the system forms a single defined phase instead of a solid solution and departs from the bixbyite structure in order to provide a 4-coordinate site for Ge [13]. approximately double the amount of tin in ITO [5,6].…”

“…The constituent identities and their site preferences have been linked to crystal structure, however, as exhibited by the cosubstitution of Zn/Ge pairs. In this instance, the system forms a single defined phase instead of a solid solution and departs from the bixbyite structure in order to provide a 4-coordinate site for Ge [13]. A thorough understanding of how multiple constituents occupy the two nonequivalent cation sites in bixbyite can provide information on how to optimize the cosubstituted systems to increase tin solubility while maintaining its dopant nature.…”