The crystal structure of solid solutions formed in the HfO2-Sc2O3 nanoscale system

• Published in: Journal of crystal growth Vol. 523; p. 125156
• Main Authors: Smirnova, T.P., Saraev, A.A., Korolkov, I.V., Kitchai, V.N., Borisov, V.O.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-10-2019; Elsevier BV
• Subjects: A1. Characterization; A1. Nanostructures; A1. Solid solutions; A1. X-ray diffraction; B1. Alloys; B1. Rare earth compounds; Complex compounds; Crystal structure; Current leakage; Electric field strength; Electron diffraction; Fluorite; Hafnium oxide; High temperature; Identification methods; Insulators; Lattice vacancies; Lattice vibration; Leakage current; MIS (semiconductors); Phases; Scandium; Scandium oxides; Solid solutions; Synthesis; Thermodynamic equilibrium; Volt-ampere characteristics; A1. Solid solutions; A1. Characterization; B1. Alloys; A1. X-ray diffraction; B1. Rare earth compounds; A1. Nanostructures
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2019.125156

•Phase formation in the Hf-Sc-O nano-system.•Impact of scandium concentration on the structural type of synthesized phases.•Approaches to phase identification.•The relationship of the physical properties and films phase composition.
Here we report the results of studying the crystal structure of solid solutions films, obtained in the HfO2-Sc2O3 nano-scale system using of ALD process and volatile complex compounds such as of Hf(N(C2H5)2)4 and [Sc(C5H4CH3). A number of phases, that are thermodynamically equilibrium at high temperatures (≥1500 °C), have been synthesized at T = 300 °C. The formation of disordered solid solutions with a fluorite structure and the Hf3Sc4O12 compound with an ordered rhombohedral structural type were observed at varying the scandium concentration from 2 to 30 at.%. The results obtained allowed to conclude that the synthesis temperature is not a parameter that determines the structural types of synthesized phases in the system under study. The formation and stabilization of the nonequilibrium high-temperature phases of solid solutions is initiated by oxygen vacancies, which accumulate when Hf is replaced by scandium in the HfO2 lattice. To identify the synthesized phases a set of methods has been used: XPS, X-ray diffraction, electron diffraction (SAED modes) and HR TEM. Testing metal-insulator-semiconductor (MIS) structures with a series of films under study has demonstrated conventional dynamic volt-ampere characteristics. The high leakage current was observed for all samples with the disordered cubic structure. The injection-type hysteresis without any current leakage signs has been observed at the electric field strength of 106 V/cm for structures with the ordered rhombohedral phase of Hf3Sc4O12.