AFM and TEM studies on high-quality Bi-2223 thin films grown by MOCVD

摘要

AFM and TEM observations of high- quality Bi-2223 thin films grown by MOCVD have been carried out to elucidate the crystal growth mechanism and the effect of surface structures on superconducting properties. AFM images of the film surfaces grown on flat planes (off-angle <0.3 deg.) of LaAlO3, SrTiO3 and MgO [001] substrates clearly showed a 2-dimensional nucleation growth. In contrast, those on vicinal planes (off-angle-3 deg.) of LaAlO3, SrTiO3 and Nd:YAlO3 [001] substrates showed a step flow growth. The films grown on LaAlO3, SrTiO3 and Nd:AlO3 showed the highest Tc(0) of 97 K reported for as-grown BSCCO films. In addition, a TEM plan-view image of the film grown on [001] LaAlO3 showed clearly the misfit dislocation network running along the orthogonal [110] directions at the heterointerface and having Burger's vectors b=1/2[110]. The clear AFM images of regularly-shaped terraces or step-edges and the distinct TEM image of the misfit dislocation network are evidence of high-quality MOCVD grown Bi-2223 films.