Properties of sputtered BaSi₂ thin films annealed in vacuum condition

As a potential absorber candidate for high-efficient solar cell applications, BaSi₂ films are confronted with issues of surface oxidation associated with the higherature annealing. Herein, BaSi₂ films are deposited by the sputtering technique. A vacuum annealing process is subsequently carried out to crystallize sputtered BaSi₂ films. Raman spectroscopy is used to study surface structures and crystalline quality. Elemental depth profile is measured by Auger Electron spectroscopy to understand the compositions of films. Optical and electrical properties are further investigated to reveal the effects of annealing condition. Applying vacuum annealing condition can effectively suppress diffusions of Ba and ensures a stochiometric BaSi₂ layer. However, surface oxidation still occurs even in the vacuum environment owing to the high reactivity of Ba. Further attempts to prevent BaSi₂ surface oxidation may focus on the combination of other methods, such as capping layer and reducing atmosphere, with vacuum (or low-pressure) annealing condition.