Thermal stability of amorphous metal chalcogenide thin films

• Published in: Journal of non-crystalline solids Vol. 559; p. 120663
• Main Authors: Sava, F., Simandan, I.D., Stavarache, I., Porosnicu, C., Mihai, C., Velea, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2021
• Subjects: Ion-conducting amorphous chalcogenides; Solid electrolytes; Thermal stability; Thin film; Solid electrolytes; Ion-conducting amorphous chalcogenides; Thermal stability; Thin film
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2021.120663

•Ag-based electrolytes have a higher thermal stability than Cu-based electrolytes.•Annealing marginally influences the ionic conduction of Ag-based electrolytes.•In the Cu-GeSe films, a Cu2-xSe superionic conducting composition is formed.•Annealing of the Cu-GeTe films above 280 °C will hinder the Cu ions diffusion.•An increase in thickness and contraction of the surface is observed at 100 °C. Amorphous metal chalcogenides have good switching properties for resistive memories, but have low thermal stability. In this work, the response to rapid thermal stress, as high as 550 °C, of amorphous Cu-GeSe, Ag-GeSe, Cu-GeTe, Ag-GeTe thin films, is investigated. Metal-GeTe films, which are amorphous up to 280 °C, are the most stable. Metal-GeSe films start to crystallize at 190 °C and a Cu1.59Se phase, with 20.5% Cu vacancies and a structure similar to the c-Cu2-xSe superionic conductor, is formed. This might boost the performance of memory devices. Silver atoms migration is facilitated in Ag-GeSe by poor crystallization (below 5%, at all temperatures). Difussion of Ag is enhanced in Ag-GeTe, due to the crystallization of the cubic (Ag2Te)4-GeTe2 (Ag8GeTe6) phase, which has Ag+ vacancies. In Cu-GeTe, the formation of stoichiometric polycrystalline Cu0.67Ge0.33Te might hinder diffusion. An unusual anisotropic behaviour (increase in thickness, simultaneously with contraction of surface) is observed at 100 °C in Cu-GeSe and Cu-GeTe thin films, which suggests the orientation of the amorphous clusters package along a preferential direction.