Quantitative measurement of structural fluctuation at LaNiO3/LaAlO3 interfaces as a function of thickness

It has been well documented that oxide films thinner than a few unit cells (u.c.) are often insulating, and the Anderson localization supported by the low dimensionality is one of the major mechanisms of such insulating behavior. To discriminate the effect of randomness from that of dimensionality, we examined structural fluctuation as well as the average structure of LaNiO3 thin films on LaAlO3 substrates as a function of thickness. The surface x-ray diffraction experiment revealed that there is little difference in average atomic position and atomic occupancy among 2 to 5 u.c. thick samples. The main difference occurs in the atomic displacement parameters. 4 and 5 u.c. thick samples have significantly smaller atomic displacement parameters than 2 and 3 u.c. thick samples. This result suggests that structural fluctuation plays some role in the interfacial transport properties although it is often neglected in the discussion of oxide interface physics.

Automated summary

It has been found that oxide films thinner than a few unit cells are often insulating, and the Anderson localization supported by low dimensionality is one of the major mechanisms for this behavior. To distinguish the effects of randomness from dimensionality, the structural fluctuation and average structure of LaNiO3 thin films on LaAlO3 substrates were examined as a function of thickness. Surface x-ray diffraction experiment revealed little difference in average atomic position and atomic occupancy between 2 to 5 u.c. thick samples, with the main difference observed in the atomic displacement parameters. This suggests that structural fluctuation plays a role in interfacial transport properties, which is often neglected in discussions of oxide interface physics.