Atomic layer deposition of cubic tin–calcium sulfide alloy films. Issue 7 (14th April 2020)

• Record Type: Journal Article
• Authors: Yang, Chuanxi; Zhao, Xizhu; Kim, Sang Bok; Schelhas, Laura T.; Lou, Xiabing; G. Gordon, Roy
• Is Part Of: Journal of materials research. Volume 35:Issue 7(2020)
• Page Start: 795
• Page End: 803
• Publication Date: 2020-04-14
• Subjects: atomic layer deposition, -- alloy, -- crystallographic structure; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1557/jmr.2019.337
• Languages: English
• ISSNs: 0884-2914

Abstract

Abstract: Abstract : We deposit films of tin–calcium sulfide by atomic layer deposition (ALD) and demonstrate the metastability of this material. Rough and spiky films are obtained by using Sn and Ca precursors with different ligands, whereas compact and smooth films are obtained when the two metal sources share the same ligands. Compositional and quartz crystal microbalance results indicate that part of the underlaying SnS film is replaced and/or removed during the CaS ALD cycle during the ternary film deposition, possibly via a temperature-dependent cation exchange mechanism. The crystal structure transforms from orthorhombic to cubic as the calcium content increases. Furthermore, resistivity increases with calcium content in the alloy films, whereas optical band gap only depends weakly on Ca content. After annealing at 400 °C in an H2 S environment, the cubic alloy film undergoes a phase transition into the orthorhombic phase and its resistivity also decreases. Both phenomena could be explained by phase separation of the metastable alloy.