STRUCTURAL CHARACTERISTICS OF La 2 O 3 THIN FILM GROWN ON LaB 6

Within the framework of hexagonal lanthanum oxide ( h - La 2 O 3 ) formation, lanthanum hexaboride film on sapphire substrate ( LaB 6 / Al 2 O 3 ) was oxidized at different temperatures (700-1000 °C) under reduced atmospheric pressure (1·10 -2 ,1.5·10 -1 Torr) during 30 min. The composition evolution of La 2 O 3 / LaB 6 structure versus annealing temperature has been studied using XRD, FIR reflectivity spectroscopy, SEM and electron probe X-ray microanalysis (EDS). The annealing of the LaB 6 film at T =700 °C under air pressure of 1·10 -2 Torr generates thin La 2 O 3 layer which exhibits as inferred from XRD the hexagonal phase. The hydratation of La 2 O 3 / LaB 6 / Al 2 O 3 in distilled water for 30 min and postannealing at 900 °C under air pressure of 1.5·10 -1 Torr transform h - La 2 O 3 into hexagonal La ( OH ) 3 phase accompanied monoclinic LaO ( OH ) and lanthanum oxide carbonate hydrate species.