Origin of Mobility Suppression in La-doped BaSnO3 Films (Ⅱ)

摘要

As discussed in the part-Ⅰ abstract, La-doped BaSnO3 (BLSO, Pm-3m, α =4.115 A,Eg〜3.1eV) epitaxial films exhibit only 〜100 cm2 V1s1 though the single crystal exhibit very high mobility of 320 cm2 V-1s-1. The main origin of mobility suppression is considered to that doped La ions were not activated at around the film/substrate interfaces. In order to clarify the origin of La inactivation, we performed LAADF-STEM observations and EELS analyses (data not shown). We have clarified that oxygen concentration at around the BLSO film and substrate interface is lower than that in the bulk region. We have also detected 2+ valence state of Sn in the BLSO film by XAS. Since Sn2+ ions play not only as electron acceptor but also ionized impurity, mobility and carrier concentration suppression occurred simultaneously.