TEM observation of ferroelectric films grown on silicon using Y2O3 buffer layer

Ferroelectric films grown on Si substrates using Y2O3 buffer layers were in vestigated by cross-sectional high-resolution transmission electron microsc opy (HRTEM). It was found that no interfacial SiO2 layer was formed when an Y2O3 layer was grown by molecular beam epitaxy (MBE) on a Si(111) substrat e at 600 degrees C, while that a SiO2 layer was formed on a Si(100) substra te under the same growth conditions. Then, ferroelectric YMnO3, SrBi2Ta2O9( SBT), and Pb(Zr,Ti)O-3(PZT) films were deposited on the Y2O3/Si structures and cross-sections were observed. It was found that the interfacial SiO2 la yer about 5 to 6 nm in the thickness was formed even on a Si(111) substrate after deposition of the ferroelectric film. It was also found that polygra ins in PZT film were much smaller than those in SBT, although both films we re formed by the same sol-gel driven method.